{"id":70,"date":"2024-09-10T22:55:54","date_gmt":"2024-09-10T14:55:54","guid":{"rendered":"https:\/\/blog.easitch.com\/?p=70"},"modified":"2026-03-18T14:25:00","modified_gmt":"2026-03-18T06:25:00","slug":"%e8%ae%b0%e4%b8%80%e6%ac%a1%e9%83%91%e5%b7%9e%e6%95%b0%e5%ad%97%e9%a9%ac%e5%8a%9b%e9%9d%a2%e8%af%95%e9%a2%98","status":"publish","type":"post","link":"https:\/\/blog.eastfond.com\/?p=70","title":{"rendered":"\u8bb0\u4e00\u6b21\u90d1\u5dde\u6570\u5b57\u9a6c\u529b\u9762\u8bd5\u9898"},"content":{"rendered":"<h1>MVCC \u7684\u5b9e\u73b0\u539f\u7406<\/h1>\n<p>\u591a\u7248\u672c\u5e76\u53d1\u63a7\u5236\uff08<strong>MVCC<\/strong>\uff0cMultiversion Concurrency Control\uff09\u662f\u4e00\u79cd\u6570\u636e\u5e93\u5e76\u53d1\u63a7\u5236\u6280\u672f\uff0c\u7528\u4e8e\u5904\u7406\u591a\u4e2a\u4e8b\u52a1\u540c\u65f6\u64cd\u4f5c\u6570\u636e\u65f6\u7684\u6570\u636e\u4e00\u81f4\u6027\u95ee\u9898\u3002\u4e0e\u9501\u673a\u5236\u4e0d\u540c\uff0cMVCC \u901a\u8fc7\u4e3a\u6bcf\u4e2a\u4e8b\u52a1\u63d0\u4f9b\u6570\u636e\u7684\u591a\u4e2a\u7248\u672c\u6765\u907f\u514d\u4e8b\u52a1\u4e4b\u95f4\u7684\u51b2\u7a81\uff0c\u5b9e\u73b0\u66f4\u9ad8\u7684\u5e76\u53d1\u6027\u3002\u4e0b\u9762\u6211\u5c06\u8be6\u7ec6\u4ecb\u7ecd MVCC \u7684\u539f\u7406\u3001\u5b9e\u73b0\u65b9\u5f0f\u4ee5\u53ca\u5b83\u89e3\u51b3\u7684\u95ee\u9898\u3002<\/p>\n<h2>\u4e00\u3001MVCC \u7684\u539f\u7406<\/h2>\n<p>MVCC \u7684\u6838\u5fc3\u601d\u60f3\u662f\uff1a\u5728\u6570\u636e\u5e93\u7cfb\u7edf\u4e2d\uff0c\u6bcf\u4e2a\u4e8b\u52a1\u5728\u8bbf\u95ee\u6570\u636e\u65f6\uff0c\u770b\u5230\u7684\u662f\u6570\u636e\u5728\u67d0\u4e2a\u65f6\u95f4\u70b9\u7684\u5feb\u7167\uff08Snapshot\uff09\uff0c\u800c\u4e0d\u662f\u6700\u65b0\u7684\u6570\u636e\u72b6\u6001\u3002\u901a\u8fc7\u7ef4\u62a4\u6570\u636e\u7684\u591a\u4e2a\u7248\u672c\uff0cMVCC \u5141\u8bb8\u591a\u4e2a\u4e8b\u52a1\u5e76\u53d1\u8bfb\u53d6\u76f8\u540c\u7684\u6570\u636e\uff0c\u4f46\u6bcf\u4e2a\u4e8b\u52a1\u8bfb\u53d6\u7684\u6570\u636e\u90fd\u662f\u5176\u81ea\u5df1\u6240\u770b\u5230\u7684\u90a3\u4e2a\u7248\u672c\uff0c\u8fd9\u6837\u53ef\u4ee5\u907f\u514d\u52a0\u9501\u5e26\u6765\u7684\u963b\u585e\u95ee\u9898\u3002<\/p>\n<p>MVCC \u4e3a\u6bcf\u4e00\u884c\u8bb0\u5f55\u4fdd\u7559\u4e86\u591a\u4e2a\u7248\u672c\uff0c\u6bcf\u4e2a\u7248\u672c\u7684\u6709\u6548\u6027\u53d6\u51b3\u4e8e\u4e8b\u52a1\u7684\u5f00\u59cb\u548c\u63d0\u4ea4\u65f6\u95f4\u3002MVCC \u5b9e\u73b0\u65f6\u901a\u5e38\u4f1a\u5f15\u5165\u5982\u4e0b\u51e0\u4e2a\u6982\u5ff5\uff1a<\/p>\n<ol>\n<li>\n<p><strong>\u4e8b\u52a1\u7684\u7248\u672c\u53f7<\/strong>\uff1a<br \/>\n\u6bcf\u4e2a\u4e8b\u52a1\u5728\u5f00\u59cb\u65f6\u4f1a\u5206\u914d\u4e00\u4e2a\u552f\u4e00\u7684\u7248\u672c\u53f7\uff08\u6216\u65f6\u95f4\u6233\uff09\uff0c\u901a\u5e38\u662f\u9012\u589e\u7684\u3002\u8fd9\u4e2a\u7248\u672c\u53f7\u7528\u4e8e\u6807\u8bb0\u4e8b\u52a1\u5728\u4f55\u65f6\u5f00\u59cb\uff0c\u5e76\u51b3\u5b9a\u8be5\u4e8b\u52a1\u53ef\u4ee5\u770b\u5230\u54ea\u4e9b\u6570\u636e\u7248\u672c\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u6570\u636e\u7684\u7248\u672c\u53f7<\/strong>\uff1a<br \/>\n\u6570\u636e\u884c\u4f1a\u7ef4\u62a4\u591a\u4e2a\u7248\u672c\uff0c\u6bcf\u4e2a\u7248\u672c\u5173\u8054\u4e00\u4e2a\u4e8b\u52a1\u53f7\u6216\u7248\u672c\u53f7\u3002\u6bcf\u4e2a\u7248\u672c\u6709\u4e24\u4e2a\u91cd\u8981\u7684\u5b57\u6bb5\uff1a<\/p>\n<ul>\n<li><strong>\u521b\u5efa\u7248\u672c\u53f7<\/strong>\uff1a\u6807\u8bc6\u8fd9\u4e2a\u7248\u672c\u662f\u7531\u54ea\u4e2a\u4e8b\u52a1\u521b\u5efa\u7684\uff08\u5199\u5165\u7684\uff09\u3002<\/li>\n<li><strong>\u5220\u9664\u7248\u672c\u53f7<\/strong>\uff1a\u6807\u8bc6\u8fd9\u4e2a\u7248\u672c\u5728\u4f55\u65f6\u88ab\u5220\u9664\uff08\u5982\u679c\u662f\u672a\u88ab\u5220\u9664\u7684\u8bb0\u5f55\uff0c\u8fd9\u4e2a\u503c\u901a\u5e38\u662f <code>NULL<\/code> \u6216\u65e0\u6548\u503c\uff09\u3002<\/li>\n<\/ul>\n<\/li>\n<li>\n<p><strong>\u5feb\u7167\u8bfb\uff08Snapshot Read\uff09<\/strong>\uff1a<br \/>\n\u4e8b\u52a1\u5728\u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u4e0d\u9700\u8981\u9501\u5b9a\u6570\u636e\uff0c\u800c\u662f\u901a\u8fc7\u5224\u65ad\u6570\u636e\u7248\u672c\u53f7\u6765\u9009\u62e9\u8bfb\u53d6\u5408\u9002\u7684\u7248\u672c\u3002\u4e8b\u52a1\u4f1a\u770b\u5230\u7684\u662f\u5728\u5176\u5f00\u59cb\u4e4b\u524d\u5df2\u63d0\u4ea4\u7684\u6570\u636e\u7248\u672c\uff0c\u4e8b\u52a1\u5f00\u59cb\u540e\u7684\u6570\u636e\u4fee\u6539\u5219\u662f\u4e0d\u53ef\u89c1\u7684\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u5f53\u524d\u8bfb\uff08Current Read\uff09<\/strong>\uff1a<br \/>\n\u67d0\u4e9b\u60c5\u51b5\u4e0b\u4e00\u4e9b\u8bfb\u64cd\u4f5c\u5e0c\u671b\u8bfb\u5230\u6700\u65b0\u7684\u6570\u636e\uff0c\u800c\u4e0d\u662f\u5feb\u7167\u4e2d\u7684\u65e7\u7248\u672c\u3002\u4f8b\u5982 <code>SELECT FOR UPDATE<\/code>\uff0c\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\u4e8b\u52a1\u4f1a\u8bfb\u53d6\u6700\u65b0\u7248\u672c\u7684\u6570\u636e\uff0c\u5e76\u53ef\u80fd\u9501\u5b9a\u8fd9\u90e8\u5206\u6570\u636e\u4ee5\u9632\u5176\u4ed6\u4e8b\u52a1\u4fee\u6539\u3002<\/p>\n<\/li>\n<\/ol>\n<h2>\u4e8c\u3001MVCC \u7684\u5b9e\u73b0<\/h2>\n<p>MVCC \u7684\u5b9e\u73b0\u4e3b\u8981\u4f9d\u8d56\u4e8e\u4e8b\u52a1\u7248\u672c\u53f7\u548c\u6570\u636e\u884c\u7684\u591a\u7248\u672c\u5b58\u50a8\u3002\u4e0d\u540c\u7684\u6570\u636e\u5e93\u7cfb\u7edf\u4f1a\u6709\u4e0d\u540c\u7684\u5177\u4f53\u5b9e\u73b0\uff0c\u4e0b\u9762\u7b80\u5355\u63cf\u8ff0\u5e38\u89c1\u7684\u5b9e\u73b0\u6b65\u9aa4\u3002<\/p>\n<ol>\n<li>\n<p><strong>\u6570\u636e\u591a\u7248\u672c\u5b58\u50a8<\/strong>\uff1a<br \/>\n\u6570\u636e\u5e93\u7cfb\u7edf\u4e2d\u6bcf\u884c\u8bb0\u5f55\u4e0d\u53ea\u4fdd\u5b58\u5f53\u524d\u7684\u6570\u636e\u72b6\u6001\uff0c\u8fd8\u4fdd\u7559\u5386\u53f2\u7248\u672c\u3002\u65b0\u7684\u66f4\u65b0\u64cd\u4f5c\u5e76\u4e0d\u4f1a\u76f4\u63a5\u8986\u76d6\u65e7\u6570\u636e\uff0c\u800c\u662f\u65b0\u5199\u5165\u4e00\u6761\u7248\u672c\u5316\u7684\u8bb0\u5f55\uff0c\u65e7\u7248\u672c\u4f9d\u7136\u4fdd\u7559\u3002\u8fd9\u4e9b\u7248\u672c\u5316\u7684\u8bb0\u5f55\u5728\u5143\u6570\u636e\u4e2d\u5b58\u50a8\u4e86\u4e8b\u52a1\u7684\u7248\u672c\u53f7\u3001\u521b\u5efa\u548c\u5220\u9664\u65f6\u95f4\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u4e8b\u52a1\u5f00\u59cb\u4e0e\u7248\u672c\u5feb\u7167<\/strong>\uff1a<br \/>\n\u6bcf\u5f53\u4e00\u4e2a\u4e8b\u52a1\u5f00\u59cb\u65f6\uff0c\u6570\u636e\u5e93\u4f1a\u5206\u914d\u4e00\u4e2a\u552f\u4e00\u7684\u65f6\u95f4\u6233\u6216\u7248\u672c\u53f7\uff0c\u5e76\u8bb0\u5f55\u4e00\u4e2a\u5feb\u7167\u3002\u8be5\u5feb\u7167\u8bb0\u5f55\u4e86\u5f53\u524d\u54ea\u4e9b\u4e8b\u52a1\u5df2\u7ecf\u63d0\u4ea4\uff0c\u54ea\u4e9b\u4e8b\u52a1\u8fd8\u672a\u63d0\u4ea4\u3002\u4e8b\u52a1\u5728\u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u4f1a\u6839\u636e\u5feb\u7167\u4e2d\u7684\u4fe1\u606f\uff0c\u8fc7\u6ee4\u6389\u90a3\u4e9b\u8fd8\u672a\u63d0\u4ea4\u7684\u66f4\u65b0\uff0c\u4fdd\u8bc1\u8bfb\u53d6\u7684\u90fd\u662f\u5df2\u7ecf\u63d0\u4ea4\u7684\u6570\u636e\u7248\u672c\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u5199\u5165\u6570\u636e\u4e0e\u7248\u672c\u7ba1\u7406<\/strong>\uff1a<br \/>\n\u5f53\u4e00\u4e2a\u4e8b\u52a1\u5bf9\u67d0\u884c\u6570\u636e\u8fdb\u884c\u66f4\u65b0\u65f6\uff0c\u6570\u636e\u5e93\u4e0d\u4f1a\u76f4\u63a5\u8986\u76d6\u8be5\u884c\u7684\u6570\u636e\uff0c\u800c\u662f\u751f\u6210\u4e00\u6761\u65b0\u7684\u7248\u672c\u8bb0\u5f55\uff0c\u5e76\u5c06\u5176\u521b\u5efa\u7248\u672c\u53f7\u8bbe\u4e3a\u5f53\u524d\u4e8b\u52a1\u7684\u7248\u672c\u53f7\uff0c\u65e7\u7248\u672c\u4f1a\u88ab\u6807\u8bb0\u4e3a\u8fc7\u65f6\uff08\u4f46\u4fdd\u7559\u5728\u6570\u636e\u5e93\u4e2d\uff0c\u76f4\u5230\u4e0d\u518d\u6709\u5176\u4ed6\u4e8b\u52a1\u9700\u8981\u8bfb\u53d6\u5b83\uff09\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u5783\u573e\u56de\u6536\uff08GC\uff0cGarbage Collection\uff09<\/strong>\uff1a<br \/>\n\u4e3a\u4e86\u907f\u514d\u65e7\u7248\u672c\u6570\u636e\u65e0\u9650\u589e\u957f\uff0c\u6570\u636e\u5e93\u7cfb\u7edf\u4f1a\u5b9a\u671f\u6e05\u7406\u90a3\u4e9b\u4e0d\u518d\u9700\u8981\u7684\u65e7\u7248\u672c\u6570\u636e\u3002\u5f53\u6240\u6709\u53ef\u80fd\u9700\u8981\u8bfb\u53d6\u67d0\u7248\u672c\u6570\u636e\u7684\u4e8b\u52a1\u90fd\u5df2\u7ed3\u675f\u65f6\uff0c\u8be5\u7248\u672c\u5c31\u53ef\u4ee5\u88ab\u56de\u6536\u3002<\/p>\n<\/li>\n<\/ol>\n<h2>\u4e09\u3001MVCC \u89e3\u51b3\u4e86\u54ea\u4e9b\u95ee\u9898<\/h2>\n<p>MVCC \u89e3\u51b3\u4e86\u4f20\u7edf\u6570\u636e\u5e93\u5728\u5e76\u53d1\u73af\u5883\u4e0b\u7684\u4e00\u4e9b\u5173\u952e\u95ee\u9898\uff0c\u5c24\u5176\u662f\u5728\u9ad8\u5e76\u53d1\u7684\u573a\u666f\u4e2d\uff0c\u5176\u4f18\u52bf\u5341\u5206\u663e\u8457\u3002\u5b83\u4e3b\u8981\u89e3\u51b3\u4e86\u4ee5\u4e0b\u95ee\u9898\uff1a<\/p>\n<ol>\n<li>\n<p><strong>\u63d0\u9ad8\u4e86\u5e76\u53d1\u6027<\/strong>\uff1a<br \/>\nMVCC \u5141\u8bb8\u591a\u4e2a\u4e8b\u52a1\u540c\u65f6\u8bfb\u53d6\u6570\u636e\u800c\u4e0d\u9700\u8981\u52a0\u9501\u3002\u7531\u4e8e\u6bcf\u4e2a\u4e8b\u52a1\u53ef\u4ee5\u770b\u5230\u81ea\u5df1\u7684\u6570\u636e\u5feb\u7167\uff0c\u8bfb\u64cd\u4f5c\u4e0d\u4f1a\u88ab\u5199\u64cd\u4f5c\u963b\u585e\uff0c\u6781\u5927\u63d0\u5347\u4e86\u7cfb\u7edf\u7684\u5e76\u53d1\u80fd\u529b\u3002\u8fd9\u4e0e\u4f20\u7edf\u7684\u9501\u673a\u5236\u76f8\u6bd4\uff0c\u907f\u514d\u4e86\u8bfb\u5199\u9501\u5b9a\u5e26\u6765\u7684\u6027\u80fd\u74f6\u9888\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u907f\u514d\u4e86\u8bfb\u5199\u51b2\u7a81<\/strong>\uff1a<br \/>\n\u5728\u4f20\u7edf\u7684\u4e24\u9636\u6bb5\u9501\u534f\u8bae\u4e2d\uff0c\u8bfb\u5199\u64cd\u4f5c\u9700\u8981\u4e92\u65a5\uff0c\u8fd9\u5bb9\u6613\u5bfc\u81f4\u8bfb\u5199\u51b2\u7a81\uff0c\u5c24\u5176\u662f\u5728\u9ad8\u5e76\u53d1\u7684\u60c5\u51b5\u4e0b\u3002\u800c MVCC \u901a\u8fc7\u591a\u7248\u672c\u7ba1\u7406\uff0c\u4f7f\u5f97\u8bfb\u64cd\u4f5c\u53ef\u4ee5\u7ee7\u7eed\u8fdb\u884c\uff0c\u800c\u5199\u64cd\u4f5c\u5219\u66f4\u65b0\u4e00\u4e2a\u65b0\u7684\u7248\u672c\uff0c\u907f\u514d\u4e86\u8bfb\u5199\u7684\u76f4\u63a5\u51b2\u7a81\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u5b9e\u73b0\u4e86\u5feb\u7167\u9694\u79bb<\/strong>\uff1a<br \/>\nMVCC \u81ea\u7136\u652f\u6301<strong>\u5feb\u7167\u9694\u79bb<\/strong>\uff08Snapshot Isolation\uff09\uff0c\u5373\u4e8b\u52a1\u770b\u5230\u7684\u90fd\u662f\u5176\u5f00\u59cb\u65f6\u7684\u6570\u636e\u5e93\u72b6\u6001\uff0c\u4e0d\u53d7\u5176\u4ed6\u672a\u63d0\u4ea4\u4e8b\u52a1\u7684\u5f71\u54cd\u3002\u8fd9\u79cd\u9694\u79bb\u7ea7\u522b\u53ef\u4ee5\u907f\u514d\u8bb8\u591a\u5e38\u89c1\u7684\u5e76\u53d1\u95ee\u9898\uff0c\u5982\u810f\u8bfb\u3001\u4e0d\u53ef\u91cd\u590d\u8bfb\u7b49\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u51cf\u5c11\u4e86\u9501\u4e89\u7528<\/strong>\uff1a<br \/>\n\u7531\u4e8e MVCC \u8bfb\u64cd\u4f5c\u4e0d\u9700\u8981\u9501\uff0c\u5199\u64cd\u4f5c\u4e5f\u4e0d\u4f1a\u963b\u585e\u8bfb\u64cd\u4f5c\uff0c\u56e0\u6b64\u51cf\u5c11\u4e86\u4e8b\u52a1\u4e4b\u95f4\u7684\u9501\u4e89\u7528\u3002\u9501\u4e89\u7528\u662f\u4f20\u7edf\u6570\u636e\u5e93\u5728\u9ad8\u5e76\u53d1\u60c5\u51b5\u4e0b\u7684\u4e3b\u8981\u74f6\u9888\u4e4b\u4e00\uff0c\u800c MVCC \u901a\u8fc7\u65e0\u9501\u7684\u65b9\u5f0f\u7ed5\u8fc7\u4e86\u8fd9\u4e2a\u95ee\u9898\u3002<\/p>\n<\/li>\n<\/ol>\n<h2>\u56db\u3001MVCC \u7684\u4e0d\u8db3\u4e0e\u6311\u6218<\/h2>\n<p>\u867d\u7136 MVCC \u63d0\u5347\u4e86\u5e76\u53d1\u6027\u80fd\uff0c\u4f46\u5b83\u4e5f\u5e26\u6765\u4e86\u4e00\u4e9b\u65b0\u7684\u6311\u6218\uff1a<\/p>\n<ol>\n<li>\n<p><strong>\u5b58\u50a8\u5f00\u9500<\/strong>\uff1a<br \/>\nMVCC \u9700\u8981\u5b58\u50a8\u591a\u4e2a\u7248\u672c\u7684\u6570\u636e\uff0c\u8fd9\u4f1a\u5bfc\u81f4\u5b58\u50a8\u5f00\u9500\u589e\u52a0\u3002\u5982\u679c\u6570\u636e\u66f4\u65b0\u9891\u7e41\uff0c\u7248\u672c\u4f1a\u8fc5\u901f\u7d2f\u79ef\uff0c\u9700\u8981\u5783\u573e\u56de\u6536\u673a\u5236\u53ca\u65f6\u6e05\u7406\uff0c\u5426\u5219\u5b58\u50a8\u7a7a\u95f4\u4f1a\u88ab\u5927\u91cf\u5386\u53f2\u7248\u672c\u5360\u7528\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u7248\u672c\u7ba1\u7406\u590d\u6742<\/strong>\uff1a<br \/>\nMVCC \u5728\u5b9e\u73b0\u4e0a\u9700\u8981\u7ef4\u62a4\u5927\u91cf\u7684\u7248\u672c\u4fe1\u606f\uff0c\u5e76\u4e14\u9700\u8981\u53ca\u65f6\u6e05\u7406\u65e0\u7528\u7684\u7248\u672c\u3002\u8fd9\u5bf9\u6570\u636e\u5e93\u7cfb\u7edf\u7684\u8bbe\u8ba1\u548c\u4f18\u5316\u63d0\u51fa\u4e86\u66f4\u9ad8\u7684\u8981\u6c42\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u4e00\u81f4\u6027\u95ee\u9898<\/strong>\uff1a<br \/>\n\u5728\u67d0\u4e9b\u60c5\u51b5\u4e0b\uff0c\u4e8b\u52a1\u53ef\u80fd\u9700\u8981\u770b\u5230\u6700\u65b0\u7684\u6570\u636e\uff08\u5982\u67d0\u4e9b\u590d\u6742\u7684\u4e1a\u52a1\u903b\u8f91\uff09\uff0c\u8fd9\u65f6\u9700\u8981\u989d\u5916\u7684\u673a\u5236\u6765\u5904\u7406\u201c\u5f53\u524d\u8bfb\u201d\u548c\u201c\u5feb\u7167\u8bfb\u201d\u4e4b\u95f4\u7684\u77db\u76fe\u3002<\/p>\n<\/li>\n<\/ol>\n<h2>\u4e94\u3001\u5178\u578b\u6570\u636e\u5e93\u4e2d\u7684 MVCC \u5b9e\u73b0<\/h2>\n<p>\u4e0d\u540c\u7684\u6570\u636e\u5e93\u7cfb\u7edf\u5bf9 MVCC \u7684\u5b9e\u73b0\u65b9\u5f0f\u6709\u6240\u4e0d\u540c\uff1a<\/p>\n<ul>\n<li>\n<p><strong>PostgreSQL<\/strong>\uff1aPostgreSQL \u4f7f\u7528 MVCC \u6765\u63d0\u4f9b\u9ad8\u5e76\u53d1\u8bbf\u95ee\u3002\u5b83\u4e3a\u6bcf\u884c\u8bb0\u5f55\u7ef4\u62a4\u4e00\u4e2a xmin \u548c xmax \u5b57\u6bb5\uff0c\u5206\u522b\u4ee3\u8868\u521b\u5efa\u8be5\u884c\u7684\u4e8b\u52a1 ID \u548c\u5220\u9664\u8be5\u884c\u7684\u4e8b\u52a1 ID\u3002\u4e8b\u52a1\u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u6839\u636e\u8fd9\u4e9b ID \u5224\u65ad\u54ea\u4e9b\u884c\u5bf9\u8be5\u4e8b\u52a1\u53ef\u89c1\u3002<\/p>\n<\/li>\n<li>\n<p><strong>MySQL InnoDB<\/strong>\uff1aInnoDB \u5f15\u64ce\u901a\u8fc7\u9690\u85cf\u7684\u7cfb\u7edf\u5217\uff08\u5982 trx_id \u548c roll_pointer\uff09\u5b9e\u73b0 MVCC\u3002trx_id \u8868\u793a\u521b\u5efa\u8be5\u7248\u672c\u7684\u4e8b\u52a1 ID\uff0croll_pointer \u6307\u5411\u56de\u6eda\u65e5\u5fd7\uff0c\u7528\u4e8e\u8ddf\u8e2a\u65e7\u7248\u672c\u7684\u6570\u636e\u3002<\/p>\n<\/li>\n<\/ul>\n<h1>\u5185\u5b58\u6ea2\u51fa\u548c\u5185\u5b58\u6cc4\u6f0f<\/h1>\n<p>\u5728 JVM\uff08Java \u865a\u62df\u673a\uff09\u4e2d\uff0c\u5185\u5b58\u6ea2\u51fa\uff08<strong>OutOfMemoryError<\/strong>\uff09\u548c\u5185\u5b58\u6cc4\u6f0f\uff08<strong>Memory Leak<\/strong>\uff09\u662f\u4e24\u79cd\u5e38\u89c1\u7684\u5185\u5b58\u95ee\u9898\uff0c\u5b83\u4eec\u867d\u7136\u6709\u4e00\u5b9a\u8054\u7cfb\uff0c\u4f46\u672c\u8d28\u4e0a\u662f\u4e0d\u540c\u7684\u6982\u5ff5\u3002\u4e0b\u9762\u6211\u4f1a\u8be6\u7ec6\u89e3\u91ca\u8fd9\u4e24\u8005\u7684\u533a\u522b\uff0c\u5e76\u901a\u8fc7\u4e3e\u4f8b\u8bf4\u660e\u5b83\u4eec\u662f\u5982\u4f55\u53d1\u751f\u7684\u3002<\/p>\n<h2>\u4e00\u3001\u5185\u5b58\u6ea2\u51fa\uff08OutOfMemoryError\uff09<\/h2>\n<h3>1. \u6982\u5ff5<\/h3>\n<p><strong>\u5185\u5b58\u6ea2\u51fa<\/strong>\u662f\u6307\u7a0b\u5e8f\u7533\u8bf7\u7684\u5185\u5b58\u8d85\u51fa\u4e86 JVM \u80fd\u5206\u914d\u7684\u6700\u5927\u5185\u5b58\u7a7a\u95f4\u3002\u5f53 JVM \u8fd0\u884c\u65f6\uff0cJVM \u4f1a\u4e3a\u5e94\u7528\u7a0b\u5e8f\u5206\u914d\u4e00\u5b9a\u7684\u5185\u5b58\u533a\u57df\uff0c\u5305\u62ec\u5806\u5185\u5b58\uff08Heap\uff09\u3001\u6808\u5185\u5b58\uff08Stack\uff09\u3001\u65b9\u6cd5\u533a\uff08Method Area\uff09\u7b49\u3002\u5982\u679c\u5e94\u7528\u7a0b\u5e8f\u9700\u8981\u7684\u5185\u5b58\u8d85\u51fa\u4e86\u8fd9\u4e9b\u533a\u57df\u7684\u9650\u5236\uff0cJVM \u5c31\u4f1a\u629b\u51fa <code>OutOfMemoryError<\/code>\u3002<\/p>\n<h3>2. \u5e38\u89c1\u7684\u5185\u5b58\u6ea2\u51fa\u573a\u666f<\/h3>\n<p><strong>\u5806\u5185\u5b58\u6ea2\u51fa\uff08Heap Space OOM\uff09<\/strong>\uff1a<\/p>\n<p>\u5806\u662f JVM \u4e2d\u7528\u4e8e\u5b58\u50a8\u5bf9\u8c61\u5b9e\u4f8b\u7684\u533a\u57df\u3002\u5f53\u5bf9\u8c61\u8fc7\u591a\uff0c\u65e0\u6cd5\u56de\u6536\u65f6\uff0c\u5c31\u53ef\u80fd\u5bfc\u81f4\u5806\u5185\u5b58\u6ea2\u51fa\u3002<\/p>\n<pre><code class=\"language-java\">public class HeapOOM {\n    public static void main(String[] args) {\n        List&lt;Object&gt; list = new ArrayList&lt;&gt;();\n        while (true) {\n            \/\/\u5728\u8fd9\u4e2a\u4f8b\u5b50\u4e2d\uff0c`ArrayList` \u4e2d\u4e0d\u65ad\u589e\u52a0\u65b0\u7684 `Object` \u5b9e\u4f8b\uff0c\u968f\u7740\u5bf9\u8c61\u8d8a\u6765\u8d8a\u591a\uff0c\u5806\u5185\u5b58\u65e0\u6cd5\u627f\u53d7\uff0c\u6700\u7ec8\u4f1a\u5bfc\u81f4 `OutOfMemoryError: Java heap space`\u3002\n            list.add(new Object());\n        }\n    }\n}<\/code><\/pre>\n<p><strong>\u6808\u5185\u5b58\u6ea2\u51fa\uff08StackOverflowError\uff09<\/strong>\uff1a<br \/>\n\u6808\u5185\u5b58\u662f JVM \u7528\u6765\u4fdd\u5b58\u65b9\u6cd5\u8c03\u7528\u6808\u5e27\u7684\u5730\u65b9\u3002\u5982\u679c\u65b9\u6cd5\u8c03\u7528\u5c42\u6b21\u8fc7\u6df1\uff0c\u6216\u8005\u9012\u5f52\u8c03\u7528\u6ca1\u6709\u9000\u51fa\u6761\u4ef6\uff0c\u6808\u5185\u5b58\u53ef\u80fd\u6ea2\u51fa\u3002<\/p>\n<pre><code class=\"language-java\">public class StackOverflow {\n    public static void main(String[] args) {\n        recursiveMethod();\n    }\n    \/\/\u8fd9\u4e2a\u9012\u5f52\u65b9\u6cd5\u6ca1\u6709\u4efb\u4f55\u9000\u51fa\u6761\u4ef6\uff0c\u56e0\u6b64\u4f1a\u4e0d\u65ad\u538b\u5165\u65b0\u7684\u6808\u5e27\uff0c\u6700\u7ec8\u5bfc\u81f4 `StackOverflowError`\u3002\n    public static void recursiveMethod() {\n        recursiveMethod(); \/\/ \u65e0\u51fa\u53e3\u7684\u9012\u5f52\u8c03\u7528\n    }\n}<\/code><\/pre>\n<p><strong>\u65b9\u6cd5\u533a\u5185\u5b58\u6ea2\u51fa\uff08Metaspace OOM\uff09<\/strong>\uff1a<br \/>\n\u65b9\u6cd5\u533a\uff08\u5728 Java 8 \u540e\u79f0\u4e3a Metaspace\uff09\u5b58\u50a8\u7c7b\u4fe1\u606f\u3001\u5e38\u91cf\u3001\u9759\u6001\u53d8\u91cf\u7b49\u3002\u5982\u679c\u52a8\u6001\u751f\u6210\u8fc7\u591a\u7684\u7c7b\uff08\u4f8b\u5982\u901a\u8fc7\u5927\u91cf\u4f7f\u7528\u53cd\u5c04\u6216\u8005\u52a8\u6001\u4ee3\u7406\uff09\uff0c\u4e5f\u53ef\u80fd\u5bfc\u81f4 Metaspace \u7684\u6ea2\u51fa\u3002<\/p>\n<h3>3. \u5185\u5b58\u6ea2\u51fa\u7684\u89e3\u51b3\u65b9\u6cd5<\/h3>\n<ul>\n<li><strong>\u8c03\u6574 JVM \u5185\u5b58\u53c2\u6570<\/strong>\uff1a\u53ef\u4ee5\u901a\u8fc7 JVM \u53c2\u6570\u5982 <code>-Xmx<\/code>\uff08\u6700\u5927\u5806\u5185\u5b58\uff09\u548c <code>-Xms<\/code>\uff08\u521d\u59cb\u5806\u5185\u5b58\uff09\u6765\u589e\u5927\u5806\u5185\u5b58\u3002<\/li>\n<li><strong>\u4f18\u5316\u4ee3\u7801<\/strong>\uff1a\u5206\u6790\u5185\u5b58\u4f7f\u7528\u60c5\u51b5\uff0c\u4f18\u5316\u5bf9\u8c61\u751f\u547d\u5468\u671f\uff0c\u907f\u514d\u4e0d\u5fc5\u8981\u7684\u5bf9\u8c61\u6301\u6709\u3002<\/li>\n<li><strong>\u51cf\u5c11\u7c7b\u52a0\u8f7d\u91cf<\/strong>\uff1a\u5bf9\u52a8\u6001\u52a0\u8f7d\u7c7b\u6216\u53cd\u5c04\u751f\u6210\u7c7b\u7684\u64cd\u4f5c\u8981\u52a0\u4ee5\u63a7\u5236\uff0c\u5fc5\u8981\u65f6\u91ca\u653e\u7c7b\u52a0\u8f7d\u5668\u3002<\/li>\n<\/ul>\n<hr \/>\n<h2>\u4e8c\u3001\u5185\u5b58\u6cc4\u6f0f\uff08Memory Leak\uff09<\/h2>\n<h3>1. \u6982\u5ff5<\/h3>\n<p><strong>\u5185\u5b58\u6cc4\u6f0f<\/strong>\u662f\u6307\u7a0b\u5e8f\u4e2d\u5b58\u5728\u4e00\u4e9b\u4e0d\u518d\u9700\u8981\u7684\u5bf9\u8c61\uff0c\u56e0\u4e3a\u67d0\u4e9b\u539f\u56e0\uff08\u5982\u5f15\u7528\u672a\u91ca\u653e\uff09\uff0c\u5bfc\u81f4\u5b83\u4eec\u65e0\u6cd5\u88ab\u5783\u573e\u56de\u6536\u5668\u56de\u6536\u3002\u8fd9\u4e9b\u5bf9\u8c61\u4f1a\u4e00\u76f4\u5360\u636e\u5185\u5b58\u7a7a\u95f4\uff0c\u5c3d\u7ba1\u7a0b\u5e8f\u903b\u8f91\u4e0a\u5df2\u7ecf\u4e0d\u518d\u9700\u8981\u5b83\u4eec\u3002<\/p>\n<p>\u5185\u5b58\u6cc4\u6f0f\u4e0d\u4f1a\u7acb\u5373\u5f15\u53d1\u5185\u5b58\u6ea2\u51fa\u9519\u8bef\uff0c\u4f46\u968f\u7740\u7a0b\u5e8f\u8fd0\u884c\u65f6\u95f4\u53d8\u957f\uff0c\u8fd9\u4e9b\u65e0\u6cd5\u91ca\u653e\u7684\u5185\u5b58\u4f1a\u79ef\u7d2f\uff0c\u6700\u7ec8\u53ef\u80fd\u5bfc\u81f4\u5185\u5b58\u6ea2\u51fa\u3002<\/p>\n<h3>2. \u5e38\u89c1\u7684\u5185\u5b58\u6cc4\u6f0f\u573a\u666f<\/h3>\n<p><strong>\u9759\u6001\u96c6\u5408\u5f15\u8d77\u7684\u5185\u5b58\u6cc4\u6f0f<\/strong>\uff1a<br \/>\n\u9759\u6001\u96c6\u5408\uff08\u5982 <code>HashMap<\/code>\u3001<code>List<\/code>\uff09\u4f1a\u968f\u7740\u7a0b\u5e8f\u7684\u8fd0\u884c\u4e00\u76f4\u5b58\u5728\uff0c\u4e14\u5176\u5185\u90e8\u5b58\u653e\u7684\u5bf9\u8c61\u4e5f\u4e0d\u4f1a\u88ab\u5783\u573e\u56de\u6536\u3002\u5982\u679c\u4e0d\u5c0f\u5fc3\u5f80\u9759\u6001\u96c6\u5408\u4e2d\u4e0d\u65ad\u6dfb\u52a0\u5bf9\u8c61\uff0c\u5e76\u4e14\u6ca1\u6709\u53ca\u65f6\u6e05\u7406\uff0c\u5c31\u4f1a\u5bfc\u81f4\u5185\u5b58\u6cc4\u6f0f\u3002<\/p>\n<pre><code class=\"language-java\">public class MemoryLeakExample {\n    private static List&lt;Object&gt; list = new ArrayList&lt;&gt;();\n\n    public static void main(String[] args) {\n        for (int i = 0; i &lt; 1000; i++) {\n            Object obj = new Object();\n            list.add(obj); \/\/ \u4e0d\u65ad\u5f80\u9759\u6001\u96c6\u5408\u4e2d\u6dfb\u52a0\u5bf9\u8c61\uff0c\u4e14\u672a\u79fb\u9664\n        }\n    }\n}<\/code><\/pre>\n<p>\u5728\u8fd9\u4e2a\u4f8b\u5b50\u4e2d\uff0c<code>list<\/code> \u662f\u9759\u6001\u7684\uff0c\u56e0\u6b64\u5373\u4f7f\u7a0b\u5e8f\u903b\u8f91\u4e0d\u518d\u9700\u8981\u5176\u4e2d\u7684\u5bf9\u8c61\uff0c\u5b83\u4eec\u4e5f\u65e0\u6cd5\u88ab\u5783\u573e\u56de\u6536\uff0c\u9020\u6210\u5185\u5b58\u6cc4\u6f0f\u3002<\/p>\n<p><strong>\u76d1\u542c\u5668\u6216\u56de\u8c03\u672a\u6b63\u786e\u79fb\u9664<\/strong>\uff1a<br \/>\n\u5982\u679c\u4e3a\u5bf9\u8c61\u6ce8\u518c\u4e86\u4e8b\u4ef6\u76d1\u542c\u5668\u6216\u56de\u8c03\uff08\u5982\u901a\u8fc7 <code>Observer<\/code> \u6a21\u5f0f\uff09\uff0c\u4f46\u6ca1\u6709\u5728\u5bf9\u8c61\u4e0d\u518d\u9700\u8981\u65f6\u53d6\u6d88\u76d1\u542c\u6216\u56de\u8c03\uff0c\u76d1\u542c\u5668\u4ecd\u7136\u6301\u6709\u5bf9\u8be5\u5bf9\u8c61\u7684\u5f15\u7528\uff0c\u5bfc\u81f4\u5bf9\u8c61\u4e0d\u80fd\u88ab\u56de\u6536<\/p>\n<pre><code class=\"language-java\">public class EventListenerLeak {\n public static void main(String[] args) {\n     Button button = new Button();\n     button.addActionListener(new ActionListener() {\n         @Override\n         public void actionPerformed(ActionEvent e) {\n             System.out.println(&quot;Button clicked&quot;);\n         }\n     });\n }\n}\n\nclass Button {\n private List&lt;ActionListener&gt; listeners = new ArrayList&lt;&gt;();\n\n public void addActionListener(ActionListener listener) {\n     listeners.add(listener); \/\/ \u76d1\u542c\u5668\u672a\u88ab\u79fb\u9664\uff0c\u6301\u6709\u5bf9 ActionListener \u7684\u5f15\u7528\n }\n}<\/code><\/pre>\n<p>\u5728\u8fd9\u4e2a\u4f8b\u5b50\u4e2d\uff0c<code>Button<\/code> \u6301\u6709 <code>ActionListener<\/code> \u7684\u5f15\u7528\uff0c\u5982\u679c <code>Button<\/code> \u4e0d\u518d\u4f7f\u7528\u5374\u672a\u91ca\u653e\u76d1\u542c\u5668\uff0c\u5c31\u4f1a\u5bfc\u81f4\u5185\u5b58\u6cc4\u6f0f\u3002<\/p>\n<p><strong>ThreadLocal \u5f15\u8d77\u7684\u5185\u5b58\u6cc4\u6f0f<\/strong>\uff1a<br \/>\n<code>ThreadLocal<\/code> \u662f\u7528\u4e8e\u4e3a\u6bcf\u4e2a\u7ebf\u7a0b\u5b58\u50a8\u79c1\u6709\u6570\u636e\u7684\u7ed3\u6784\uff0c\u4f46\u5982\u679c <code>ThreadLocal<\/code> \u6ca1\u6709\u88ab\u6b63\u786e\u6e05\u7406\uff0c\u4e5f\u53ef\u80fd\u4f1a\u5bfc\u81f4\u7ebf\u7a0b\u7ed3\u675f\u540e\u4ecd\u7136\u65e0\u6cd5\u91ca\u653e\u7ebf\u7a0b\u79c1\u6709\u7684\u6570\u636e\u3002<\/p>\n<pre><code class=\"language-java\">public class ThreadLocalLeak {\n    private static final ThreadLocal&lt;byte[]&gt; threadLocal = new ThreadLocal&lt;&gt;();\n\n    public static void main(String[] args) {\n        threadLocal.set(new byte[1024 * 1024 * 10]); \/\/ 10MB \u7684\u5bf9\u8c61\n        \/\/ \u5982\u679c\u4e0d\u8c03\u7528 threadLocal.remove()\uff0c\u5bf9\u8c61\u5c06\u65e0\u6cd5\u88ab\u56de\u6536\n    }\n}<\/code><\/pre>\n<p>\u5728\u8fd9\u4e2a\u4f8b\u5b50\u4e2d\uff0c\u5982\u679c\u7ebf\u7a0b\u7ed3\u675f\u540e\u672a\u663e\u5f0f\u8c03\u7528 <code>threadLocal.remove()<\/code>\uff0c\u5219 <code>ThreadLocal<\/code> \u5f15\u7528\u7684\u5bf9\u8c61\u5c06\u65e0\u6cd5\u88ab\u56de\u6536\uff0c\u5bfc\u81f4\u5185\u5b58\u6cc4\u6f0f\u3002<\/p>\n<h3>3. \u5185\u5b58\u6cc4\u6f0f\u7684\u89e3\u51b3\u65b9\u6cd5<\/h3>\n<ul>\n<li><strong>\u9759\u6001\u5f15\u7528\u7684\u6e05\u7406<\/strong>\uff1a\u907f\u514d\u5728\u9759\u6001\u96c6\u5408\u4e2d\u65e0\u9650\u5236\u5b58\u653e\u5bf9\u8c61\uff0c\u4f7f\u7528\u5b8c\u4e4b\u540e\u53ca\u65f6\u79fb\u9664\u3002<\/li>\n<li><strong>\u76d1\u542c\u5668\u548c\u56de\u8c03\u7684\u89e3\u9664<\/strong>\uff1a\u5728\u5bf9\u8c61\u751f\u547d\u5468\u671f\u7ed3\u675f\u65f6\uff0c\u786e\u4fdd\u79fb\u9664\u6ce8\u518c\u7684\u76d1\u542c\u5668\u6216\u56de\u8c03\u3002<\/li>\n<li><strong>ThreadLocal \u7684\u6b63\u786e\u4f7f\u7528<\/strong>\uff1a\u5728\u4f7f\u7528 <code>ThreadLocal<\/code> \u65f6\uff0c\u5728\u5408\u9002\u7684\u65f6\u5019\u8c03\u7528 <code>remove()<\/code> \u65b9\u6cd5\uff0c\u786e\u4fdd\u7ebf\u7a0b\u7ed3\u675f\u540e\u6570\u636e\u53ef\u4ee5\u88ab\u56de\u6536\u3002<\/li>\n<\/ul>\n<hr \/>\n<h2>\u4e09\u3001\u5185\u5b58\u6ea2\u51fa vs \u5185\u5b58\u6cc4\u6f0f<\/h2>\n<table>\n<thead>\n<tr>\n<th>\u7279\u6027<\/th>\n<th>\u5185\u5b58\u6ea2\u51fa\uff08OutOfMemoryError\uff09<\/th>\n<th>\u5185\u5b58\u6cc4\u6f0f\uff08Memory Leak\uff09<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>\u89e6\u53d1\u6761\u4ef6<\/td>\n<td>JVM \u7684\u67d0\u4e2a\u5185\u5b58\u533a\u57df\u8017\u5c3d\uff0c\u65e0\u6cd5\u518d\u5206\u914d\u5185\u5b58<\/td>\n<td>\u7a0b\u5e8f\u4e2d\u4e0d\u518d\u4f7f\u7528\u7684\u5bf9\u8c61\u65e0\u6cd5\u88ab\u5783\u573e\u56de\u6536<\/td>\n<\/tr>\n<tr>\n<td>\u5f02\u5e38\/\u9519\u8bef\u7c7b\u578b<\/td>\n<td>\u76f4\u63a5\u629b\u51fa <code>OutOfMemoryError<\/code> \u5f02\u5e38<\/td>\n<td>\u901a\u5e38\u4e0d\u4f1a\u7acb\u5373\u629b\u5f02\u5e38\uff0c\u4f46\u957f\u65f6\u95f4\u8fd0\u884c\u4f1a\u5bfc\u81f4\u5185\u5b58\u6ea2\u51fa<\/td>\n<\/tr>\n<tr>\n<td>\u5f71\u54cd\u8303\u56f4<\/td>\n<td>\u7a0b\u5e8f\u5185\u5b58\u8017\u5c3d\uff0c\u65e0\u6cd5\u7ee7\u7eed\u6267\u884c\uff0c\u7acb\u5373\u5bfc\u81f4\u7a0b\u5e8f\u5d29\u6e83<\/td>\n<td>\u7a0b\u5e8f\u5185\u5b58\u9010\u6e10\u589e\u52a0\uff0c\u6700\u7ec8\u53ef\u80fd\u5bfc\u81f4\u5185\u5b58\u6ea2\u51fa<\/td>\n<\/tr>\n<tr>\n<td>\u5178\u578b\u573a\u666f<\/td>\n<td>\u521b\u5efa\u8fc7\u591a\u5bf9\u8c61\u3001\u9012\u5f52\u8c03\u7528\u8fc7\u6df1\u3001\u751f\u6210\u8fc7\u591a\u7c7b\u6216\u65b9\u6cd5\u7b49<\/td>\n<td>\u9759\u6001\u5f15\u7528\u672a\u91ca\u653e\u3001\u76d1\u542c\u5668\u672a\u79fb\u9664\u3001ThreadLocal \u672a\u6e05\u7406\u7b49<\/td>\n<\/tr>\n<tr>\n<td>\u89e3\u51b3\u65b9\u5f0f<\/td>\n<td>\u589e\u5927 JVM \u5185\u5b58\u53c2\u6570\uff0c\u4f18\u5316\u5bf9\u8c61\u5206\u914d\uff0c\u907f\u514d\u5927\u5bf9\u8c61\u5360\u7528\u8fc7\u591a\u5185\u5b58<\/td>\n<td>\u4f18\u5316\u5f15\u7528\u7ba1\u7406\uff0c\u53ca\u65f6\u91ca\u653e\u4e0d\u518d\u4f7f\u7528\u7684\u5bf9\u8c61<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h3>\u7ed3\u8bba<\/h3>\n<p>\u5185\u5b58\u6ea2\u51fa\u548c\u5185\u5b58\u6cc4\u6f0f\u662f JVM \u4e2d\u5e38\u89c1\u7684\u5185\u5b58\u95ee\u9898\u3002\u5185\u5b58\u6ea2\u51fa\u901a\u5e38\u7531\u4e8e\u5206\u914d\u7684\u5185\u5b58\u8d85\u8fc7\u4e86 JVM \u7684\u9650\u5236\uff0c\u800c\u5185\u5b58\u6cc4\u6f0f\u662f\u56e0\u4e3a\u7a0b\u5e8f\u4e2d\u6709\u672a\u91ca\u653e\u7684\u5bf9\u8c61\u3002\u5185\u5b58\u6ea2\u51fa\u4f1a\u7acb\u5373\u5bfc\u81f4\u7a0b\u5e8f\u5d29\u6e83\uff0c\u800c\u5185\u5b58\u6cc4\u6f0f\u5219\u662f\u6f5c\u5728\u95ee\u9898\uff0c\u957f\u671f\u79ef\u7d2f\u53ef\u80fd\u5bfc\u81f4\u5185\u5b58\u6ea2\u51fa\u3002\u901a\u8fc7\u5408\u7406\u7684\u5185\u5b58\u7ba1\u7406\u548c\u4ee3\u7801\u4f18\u5316\uff0c\u53ef\u4ee5\u6709\u6548\u51cf\u5c11\u8fd9\u4e9b\u95ee\u9898\u7684\u53d1\u751f\u3002<\/p>\n<h1>Bean\u7684\u521b\u5efa\u8fc7\u7a0b<\/h1>\n<p>\u5728 Spring \u6846\u67b6\u4e2d\uff0cBean \u7684\u521b\u5efa\u8fc7\u7a0b\u662f\u4e00\u4e2a\u590d\u6742\u4f46\u6709\u5e8f\u7684\u8fc7\u7a0b\uff0c\u6d89\u53ca\u591a\u4e2a\u6b65\u9aa4\u548c\u7ec4\u4ef6\u3002\u4ee5\u4e0b\u662f Spring Bean \u521b\u5efa\u8fc7\u7a0b\u7684\u4e3b\u8981\u6b65\u9aa4\uff1a<\/p>\n<h2>1. <strong>BeanDefinition \u7684\u52a0\u8f7d<\/strong><\/h2>\n<ul>\n<li><strong>BeanDefinition<\/strong> \u662f Spring \u4e2d\u7528\u4e8e\u63cf\u8ff0 Bean \u7684\u5143\u6570\u636e\u5bf9\u8c61\u3002Spring \u5bb9\u5668\u5728\u542f\u52a8\u65f6\u4f1a\u4ece\u914d\u7f6e\u6587\u4ef6\uff08\u5982 XML \u6587\u4ef6\u3001Java \u914d\u7f6e\u7c7b\u3001\u6ce8\u89e3\u7b49\uff09\u4e2d\u52a0\u8f7d Bean \u7684\u5b9a\u4e49\u4fe1\u606f\uff0c\u5e76\u5c06\u5176\u8f6c\u6362\u4e3a <code>BeanDefinition<\/code> \u5bf9\u8c61\u3002<\/li>\n<li>\u52a0\u8f7d\u65b9\u5f0f\u5305\u62ec\uff1a\n<ul>\n<li><strong>XML \u914d\u7f6e\u6587\u4ef6<\/strong>\uff1a\u901a\u8fc7 <code>ClassPathXmlApplicationContext<\/code> \u6216 <code>FileSystemXmlApplicationContext<\/code> \u52a0\u8f7d XML \u6587\u4ef6\u3002<\/li>\n<li><strong>Java \u914d\u7f6e\u7c7b<\/strong>\uff1a\u901a\u8fc7 <code>AnnotationConfigApplicationContext<\/code> \u52a0\u8f7d\u5e26\u6709 <code>@Configuration<\/code> \u6ce8\u89e3\u7684 Java \u7c7b\u3002<\/li>\n<li><strong>\u6ce8\u89e3\u626b\u63cf<\/strong>\uff1a\u901a\u8fc7 <code>@ComponentScan<\/code> \u6ce8\u89e3\u626b\u63cf\u6307\u5b9a\u5305\u4e0b\u7684\u7c7b\uff0c\u5e76\u81ea\u52a8\u6ce8\u518c\u4e3a Bean\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h2>2. <strong>BeanDefinition \u7684\u6ce8\u518c<\/strong><\/h2>\n<ul>\n<li>\u52a0\u8f7d\u7684 <code>BeanDefinition<\/code> \u4f1a\u88ab\u6ce8\u518c\u5230 Spring \u5bb9\u5668\u7684 <code>BeanDefinitionRegistry<\/code> \u4e2d\u3002Spring \u5bb9\u5668\u4f1a\u7ef4\u62a4\u4e00\u4e2a <code>BeanDefinitionMap<\/code>\uff0c\u7528\u4e8e\u5b58\u50a8\u6240\u6709 Bean \u7684\u5b9a\u4e49\u4fe1\u606f\u3002<\/li>\n<\/ul>\n<h2>3. <strong>Bean \u7684\u5b9e\u4f8b\u5316<\/strong><\/h2>\n<ul>\n<li>\u5f53 Spring \u5bb9\u5668\u9700\u8981\u521b\u5efa\u67d0\u4e2a Bean \u65f6\uff0c\u4f1a\u6839\u636e <code>BeanDefinition<\/code> \u4e2d\u7684\u4fe1\u606f\u8fdb\u884c\u5b9e\u4f8b\u5316\u3002\u5b9e\u4f8b\u5316\u8fc7\u7a0b\u901a\u5e38\u5305\u62ec\u4ee5\u4e0b\u6b65\u9aa4\uff1a\n<ul>\n<li><strong>\u9009\u62e9\u6784\u9020\u5668<\/strong>\uff1aSpring \u4f1a\u6839\u636e <code>BeanDefinition<\/code> \u4e2d\u7684\u4fe1\u606f\u9009\u62e9\u5408\u9002\u7684\u6784\u9020\u5668\u8fdb\u884c\u5b9e\u4f8b\u5316\u3002\u5982\u679c Bean \u7c7b\u6709\u591a\u4e2a\u6784\u9020\u5668\uff0cSpring \u4f1a\u6839\u636e\u914d\u7f6e\u6216\u9ed8\u8ba4\u89c4\u5219\u9009\u62e9\u4e00\u4e2a\u3002<\/li>\n<li><strong>\u5b9e\u4f8b\u5316\u5bf9\u8c61<\/strong>\uff1aSpring \u4f7f\u7528\u53cd\u5c04\u673a\u5236\u8c03\u7528\u6784\u9020\u5668\u521b\u5efa\u5bf9\u8c61\u5b9e\u4f8b\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h2>4. <strong>Bean \u7684\u5c5e\u6027\u6ce8\u5165<\/strong><\/h2>\n<ul>\n<li>\u5b9e\u4f8b\u5316\u5b8c\u6210\u540e\uff0cSpring \u4f1a\u6839\u636e <code>BeanDefinition<\/code> \u4e2d\u7684\u4fe1\u606f\u8fdb\u884c\u5c5e\u6027\u6ce8\u5165\u3002\u5c5e\u6027\u6ce8\u5165\u7684\u65b9\u5f0f\u5305\u62ec\uff1a\n<ul>\n<li><strong>Setter \u6ce8\u5165<\/strong>\uff1a\u901a\u8fc7\u8c03\u7528 Bean \u7684 setter \u65b9\u6cd5\u6ce8\u5165\u4f9d\u8d56\u3002<\/li>\n<li><strong>\u6784\u9020\u5668\u6ce8\u5165<\/strong>\uff1a\u901a\u8fc7\u6784\u9020\u5668\u53c2\u6570\u6ce8\u5165\u4f9d\u8d56\u3002<\/li>\n<li><strong>\u5b57\u6bb5\u6ce8\u5165<\/strong>\uff1a\u901a\u8fc7\u53cd\u5c04\u76f4\u63a5\u6ce8\u5165\u5b57\u6bb5\uff08\u901a\u5e38\u4f7f\u7528 <code>@Autowired<\/code> \u6ce8\u89e3\uff09\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h2>5. <strong>Bean \u7684\u521d\u59cb\u5316<\/strong><\/h2>\n<ul>\n<li>\u5c5e\u6027\u6ce8\u5165\u5b8c\u6210\u540e\uff0cSpring \u4f1a\u8c03\u7528 Bean \u7684\u521d\u59cb\u5316\u65b9\u6cd5\u3002\u521d\u59cb\u5316\u65b9\u6cd5\u53ef\u4ee5\u901a\u8fc7\u4ee5\u4e0b\u65b9\u5f0f\u5b9a\u4e49\uff1a\n<ul>\n<li><strong><code>@PostConstruct<\/code> \u6ce8\u89e3<\/strong>\uff1a\u5728 Bean \u521d\u59cb\u5316\u5b8c\u6210\u540e\u8c03\u7528\u5e26\u6709 <code>@PostConstruct<\/code> \u6ce8\u89e3\u7684\u65b9\u6cd5\u3002<\/li>\n<li><strong><code>InitializingBean<\/code> \u63a5\u53e3<\/strong>\uff1a\u5b9e\u73b0 <code>InitializingBean<\/code> \u63a5\u53e3\uff0c\u5e76\u91cd\u5199 <code>afterPropertiesSet()<\/code> \u65b9\u6cd5\u3002<\/li>\n<li><strong>\u81ea\u5b9a\u4e49\u521d\u59cb\u5316\u65b9\u6cd5<\/strong>\uff1a\u5728 <code>BeanDefinition<\/code> \u4e2d\u6307\u5b9a\u81ea\u5b9a\u4e49\u7684\u521d\u59cb\u5316\u65b9\u6cd5\u540d\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h2>6. <strong>Bean \u7684\u4ee3\u7406\uff08\u5982\u679c\u6709\uff09<\/strong><\/h2>\n<ul>\n<li>\u5982\u679c Bean \u9700\u8981\u8fdb\u884c AOP \u4ee3\u7406\uff0cSpring \u4f1a\u5728\u521d\u59cb\u5316\u5b8c\u6210\u540e\u521b\u5efa\u4ee3\u7406\u5bf9\u8c61\u3002\u4ee3\u7406\u5bf9\u8c61\u4f1a\u5305\u88c5\u539f\u59cb Bean\uff0c\u5e76\u5728\u8c03\u7528\u65b9\u6cd5\u65f6\u6267\u884c\u989d\u5916\u7684\u903b\u8f91\uff08\u5982\u4e8b\u52a1\u7ba1\u7406\u3001\u65e5\u5fd7\u8bb0\u5f55\u7b49\uff09\u3002<\/li>\n<\/ul>\n<h2>7. <strong>Bean \u7684\u6ce8\u518c<\/strong><\/h2>\n<ul>\n<li>\u521d\u59cb\u5316\u5b8c\u6210\u540e\uff0cSpring \u4f1a\u5c06 Bean \u5b9e\u4f8b\u6ce8\u518c\u5230\u5bb9\u5668\u7684\u5355\u4f8b\u7f13\u5b58\u4e2d\uff08<code>singletonObjects<\/code>\uff09\uff0c\u4ee5\u4fbf\u540e\u7eed\u53ef\u4ee5\u76f4\u63a5\u4ece\u7f13\u5b58\u4e2d\u83b7\u53d6 Bean \u5b9e\u4f8b\u3002<\/li>\n<\/ul>\n<h2>8. <strong>Bean \u7684\u4f7f\u7528<\/strong><\/h2>\n<ul>\n<li>\u5f53\u5e94\u7528\u7a0b\u5e8f\u9700\u8981\u4f7f\u7528\u67d0\u4e2a Bean \u65f6\uff0cSpring \u5bb9\u5668\u4f1a\u4ece\u5355\u4f8b\u7f13\u5b58\u4e2d\u83b7\u53d6 Bean \u5b9e\u4f8b\u5e76\u8fd4\u56de\u3002\u5982\u679c Bean \u662f\u539f\u578b\uff08Prototype\uff09\u4f5c\u7528\u57df\uff0cSpring \u5bb9\u5668\u4f1a\u5728\u6bcf\u6b21\u8bf7\u6c42\u65f6\u521b\u5efa\u65b0\u7684\u5b9e\u4f8b\u3002<\/li>\n<\/ul>\n<h2>9. <strong>Bean \u7684\u9500\u6bc1<\/strong><\/h2>\n<ul>\n<li>\u5f53 Spring \u5bb9\u5668\u5173\u95ed\u65f6\uff0c\u4f1a\u9500\u6bc1\u6240\u6709\u5355\u4f8b Bean\u3002\u9500\u6bc1\u8fc7\u7a0b\u5305\u62ec\uff1a\n<ul>\n<li><strong>\u8c03\u7528\u9500\u6bc1\u65b9\u6cd5<\/strong>\uff1a\u5982\u679c Bean \u5b9e\u73b0\u4e86 <code>DisposableBean<\/code> \u63a5\u53e3\uff0cSpring \u4f1a\u8c03\u7528 <code>destroy()<\/code> \u65b9\u6cd5\u3002<\/li>\n<li><strong>\u8c03\u7528 <code>@PreDestroy<\/code> \u6ce8\u89e3\u7684\u65b9\u6cd5<\/strong>\uff1aSpring \u4f1a\u8c03\u7528\u5e26\u6709 <code>@PreDestroy<\/code> \u6ce8\u89e3\u7684\u65b9\u6cd5\u3002<\/li>\n<li><strong>\u8c03\u7528\u81ea\u5b9a\u4e49\u9500\u6bc1\u65b9\u6cd5<\/strong>\uff1a\u5728 <code>BeanDefinition<\/code> \u4e2d\u6307\u5b9a\u7684\u81ea\u5b9a\u4e49\u9500\u6bc1\u65b9\u6cd5\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h1>CAS \u673a\u5236<\/h1>\n<p>CAS\uff08Compare-And-Swap\uff09\u662f\u4e00\u79cd\u5e76\u53d1\u7f16\u7a0b\u4e2d\u7684\u539f\u5b50\u64cd\u4f5c\u673a\u5236\uff0c\u7528\u4e8e\u5b9e\u73b0\u65e0\u9501\uff08lock-free\uff09\u7684\u6570\u636e\u7ed3\u6784\u548c\u7b97\u6cd5\u3002CAS \u64cd\u4f5c\u901a\u5e38\u7528\u4e8e\u591a\u7ebf\u7a0b\u73af\u5883\u4e0b\uff0c\u786e\u4fdd\u5bf9\u5171\u4eab\u53d8\u91cf\u7684\u66f4\u65b0\u662f\u539f\u5b50\u7684\uff0c\u4ece\u800c\u907f\u514d\u6570\u636e\u7ade\u4e89\u548c\u5e76\u53d1\u95ee\u9898\u3002<\/p>\n<h2>CAS \u7684\u57fa\u672c\u6982\u5ff5<\/h2>\n<p>CAS \u64cd\u4f5c\u5305\u542b\u4e09\u4e2a\u64cd\u4f5c\u6570\uff1a<\/p>\n<ul>\n<li><strong>\u5185\u5b58\u4f4d\u7f6e\uff08V\uff09<\/strong>\uff1a\u8981\u66f4\u65b0\u7684\u53d8\u91cf\u5728\u5185\u5b58\u4e2d\u7684\u5730\u5740\u3002<\/li>\n<li><strong>\u9884\u671f\u503c\uff08A\uff09<\/strong>\uff1a\u5f53\u524d\u7ebf\u7a0b\u8ba4\u4e3a\u8be5\u53d8\u91cf\u5728\u5185\u5b58\u4e2d\u7684\u503c\u3002<\/li>\n<li><strong>\u65b0\u503c\uff08B\uff09<\/strong>\uff1a\u7ebf\u7a0b\u5e0c\u671b\u5c06\u53d8\u91cf\u66f4\u65b0\u4e3a\u7684\u65b0\u503c\u3002<\/li>\n<\/ul>\n<p>CAS \u64cd\u4f5c\u7684\u903b\u8f91\u5982\u4e0b\uff1a<\/p>\n<ol>\n<li><strong>\u6bd4\u8f83<\/strong>\uff1a\u68c0\u67e5\u5185\u5b58\u4f4d\u7f6e V \u4e2d\u7684\u503c\u662f\u5426\u7b49\u4e8e\u9884\u671f\u503c A\u3002<\/li>\n<li><strong>\u66f4\u65b0<\/strong>\uff1a\u5982\u679c\u76f8\u7b49\uff0c\u5219\u5c06\u5185\u5b58\u4f4d\u7f6e V \u4e2d\u7684\u503c\u66f4\u65b0\u4e3a\u65b0\u503c B\uff0c\u5e76\u8fd4\u56de\u6210\u529f\u3002<\/li>\n<li><strong>\u5931\u8d25<\/strong>\uff1a\u5982\u679c\u4e0d\u76f8\u7b49\uff0c\u5219\u4e0d\u8fdb\u884c\u66f4\u65b0\uff0c\u5e76\u8fd4\u56de\u5931\u8d25\u3002<\/li>\n<\/ol>\n<p>CAS \u64cd\u4f5c\u662f\u539f\u5b50\u7684\uff0c\u8fd9\u610f\u5473\u7740\u5728\u591a\u7ebf\u7a0b\u73af\u5883\u4e0b\uff0c\u53ea\u6709\u4e00\u4e2a\u7ebf\u7a0b\u80fd\u591f\u6210\u529f\u6267\u884c CAS \u64cd\u4f5c\uff0c\u5176\u4ed6\u7ebf\u7a0b\u4f1a\u5931\u8d25\u5e76\u9700\u8981\u91cd\u8bd5\u3002<\/p>\n<h2>CAS \u7684\u5b9e\u73b0<\/h2>\n<p>CAS \u64cd\u4f5c\u901a\u5e38\u7531\u5e95\u5c42\u786c\u4ef6\u6307\u4ee4\uff08\u5982 x86 \u67b6\u6784\u4e2d\u7684 <code>CMPXCHG<\/code> \u6307\u4ee4\uff09\u76f4\u63a5\u652f\u6301\uff0c\u56e0\u6b64\u5177\u6709\u6781\u9ad8\u7684\u6027\u80fd\u548c\u53ef\u9760\u6027\u3002\u5728\u9ad8\u7ea7\u7f16\u7a0b\u8bed\u8a00\u4e2d\uff0cCAS \u64cd\u4f5c\u901a\u5e38\u901a\u8fc7\u5e93\u51fd\u6570\u6216\u539f\u5b50\u7c7b\u6765\u5b9e\u73b0\u3002<\/p>\n<h2>CAS \u7684\u5e94\u7528\u573a\u666f<\/h2>\n<p>CAS \u673a\u5236\u5e7f\u6cdb\u5e94\u7528\u4e8e\u5e76\u53d1\u7f16\u7a0b\u4e2d\uff0c\u7279\u522b\u662f\u5728\u4ee5\u4e0b\u573a\u666f\uff1a<\/p>\n<ol>\n<li><strong>\u65e0\u9501\u6570\u636e\u7ed3\u6784<\/strong>\uff1a\u5982\u65e0\u9501\u961f\u5217\u3001\u65e0\u9501\u6808\u7b49\u3002\u901a\u8fc7 CAS \u64cd\u4f5c\uff0c\u53ef\u4ee5\u5728\u4e0d\u4f7f\u7528\u9501\u7684\u60c5\u51b5\u4e0b\u5b9e\u73b0\u7ebf\u7a0b\u5b89\u5168\u7684\u6570\u636e\u7ed3\u6784\u3002<\/li>\n<li><strong>\u539f\u5b50\u53d8\u91cf<\/strong>\uff1a\u5982 Java \u4e2d\u7684 <code>AtomicInteger<\/code>\u3001<code>AtomicLong<\/code> \u7b49\u7c7b\uff0c\u63d0\u4f9b\u4e86\u57fa\u4e8e CAS \u7684\u539f\u5b50\u64cd\u4f5c\u3002<\/li>\n<li><strong>\u81ea\u65cb\u9501<\/strong>\uff1a\u901a\u8fc7 CAS \u64cd\u4f5c\u5b9e\u73b0\u7684\u81ea\u65cb\u9501\uff0c\u53ef\u4ee5\u5728\u7b49\u5f85\u9501\u65f6\u907f\u514d\u7ebf\u7a0b\u5207\u6362\u7684\u5f00\u9500\u3002<\/li>\n<\/ol>\n<h2>CAS \u7684\u4f18\u7f3a\u70b9<\/h2>\n<h3>\u4f18\u70b9<\/h3>\n<ul>\n<li><strong>\u9ad8\u6027\u80fd<\/strong>\uff1aCAS \u64cd\u4f5c\u901a\u5e38\u7531\u786c\u4ef6\u6307\u4ee4\u76f4\u63a5\u652f\u6301\uff0c\u5177\u6709\u6781\u9ad8\u7684\u6027\u80fd\u3002<\/li>\n<li><strong>\u65e0\u9501<\/strong>\uff1a\u907f\u514d\u4e86\u4f20\u7edf\u9501\u673a\u5236\u4e2d\u7684\u7ebf\u7a0b\u963b\u585e\u548c\u4e0a\u4e0b\u6587\u5207\u6362\u5f00\u9500\u3002<\/li>\n<li><strong>\u7b80\u5355<\/strong>\uff1aCAS \u64cd\u4f5c\u903b\u8f91\u7b80\u5355\uff0c\u6613\u4e8e\u7406\u89e3\u548c\u5b9e\u73b0\u3002<\/li>\n<\/ul>\n<h3>\u7f3a\u70b9<\/h3>\n<ul>\n<li><strong>ABA \u95ee\u9898<\/strong>\uff1aCAS \u64cd\u4f5c\u5728\u6bd4\u8f83\u548c\u4ea4\u6362\u8fc7\u7a0b\u4e2d\uff0c\u5982\u679c\u53d8\u91cf\u7684\u503c\u4ece A \u53d8\u4e3a B \u518d\u53d8\u56de A\uff0cCAS \u64cd\u4f5c\u4f1a\u8ba4\u4e3a\u53d8\u91cf\u6ca1\u6709\u53d8\u5316\uff0c\u4ece\u800c\u5bfc\u81f4\u9519\u8bef\u7684\u66f4\u65b0\u3002\u89e3\u51b3 ABA \u95ee\u9898\u7684\u65b9\u6cd5\u5305\u62ec\u4f7f\u7528\u7248\u672c\u53f7\u6216\u6807\u8bb0\u4f4d\u3002<\/li>\n<li><strong>\u81ea\u65cb\u5f00\u9500<\/strong>\uff1a\u5728\u7ade\u4e89\u6fc0\u70c8\u7684\u60c5\u51b5\u4e0b\uff0cCAS \u64cd\u4f5c\u53ef\u80fd\u4f1a\u5bfc\u81f4\u7ebf\u7a0b\u4e0d\u65ad\u81ea\u65cb\uff08\u91cd\u8bd5\uff09\uff0c\u6d88\u8017 CPU \u8d44\u6e90\u3002<\/li>\n<\/ul>\n<h2>CAS \u7684\u4ee3\u7801\u793a\u4f8b<\/h2>\n<p>\u4ee5\u4e0b\u662f\u4e00\u4e2a\u7b80\u5355\u7684 Java \u793a\u4f8b\uff0c\u5c55\u793a\u4e86\u5982\u4f55\u4f7f\u7528 <code>AtomicInteger<\/code> \u7c7b\u4e2d\u7684 CAS \u64cd\u4f5c\uff1a<\/p>\n<pre><code class=\"language-java\">import java.util.concurrent.atomic.AtomicInteger;\n\npublic class CASExample {\n    private static AtomicInteger counter = new AtomicInteger(0);\n\n    public static void main(String[] args) {\n        \/\/ \u521b\u5efa\u591a\u4e2a\u7ebf\u7a0b\u5e76\u53d1\u5730\u589e\u52a0\u8ba1\u6570\u5668\n        for (int i = 0; i &lt; 10; i++) {\n            new Thread(() -&gt; {\n                for (int j = 0; j &lt; 1000; j++) {\n                    \/\/ \u4f7f\u7528 CAS \u64cd\u4f5c\u589e\u52a0\u8ba1\u6570\u5668\n                    int expectedValue;\n                    int newValue;\n                    do {\n                        expectedValue = counter.get();\n                        newValue = expectedValue + 1;\n                    } while (!counter.compareAndSet(expectedValue, newValue));\n                }\n            }).start();\n        }\n\n        \/\/ \u7b49\u5f85\u6240\u6709\u7ebf\u7a0b\u5b8c\u6210\n        try {\n            Thread.sleep(2000);\n        } catch (InterruptedException e) {\n            e.printStackTrace();\n        }\n\n        \/\/ \u8f93\u51fa\u6700\u7ec8\u7684\u8ba1\u6570\u5668\u503c\n        System.out.println(&quot;Final counter value: &quot; + counter.get());\n    }\n}<\/code><\/pre>\n<p>\u5728\u8fd9\u4e2a\u793a\u4f8b\u4e2d\uff0c\u591a\u4e2a\u7ebf\u7a0b\u5e76\u53d1\u5730\u589e\u52a0\u4e00\u4e2a <code>AtomicInteger<\/code> \u7c7b\u578b\u7684\u8ba1\u6570\u5668\u3002<code>compareAndSet<\/code> \u65b9\u6cd5\u4f7f\u7528\u4e86 CAS \u64cd\u4f5c\uff0c\u786e\u4fdd\u6bcf\u6b21\u589e\u52a0\u64cd\u4f5c\u90fd\u662f\u539f\u5b50\u7684\u3002<\/p>\n<h1>ReentrantLock\u7684\u5b9e\u73b0<\/h1>\n<p><code>ReentrantLock<\/code> \u662f Java \u4e2d\u63d0\u4f9b\u7684\u4e00\u79cd\u53ef\u91cd\u5165\u7684\u4e92\u65a5\u9501\uff08Reentrant Mutex Lock\uff09\uff0c\u5b83\u5b9e\u73b0\u4e86 <code>Lock<\/code> \u63a5\u53e3\uff0c\u5e76\u4e14\u63d0\u4f9b\u4e86\u6bd4\u4f20\u7edf\u7684 <code>synchronized<\/code> \u5173\u952e\u5b57\u66f4\u7075\u6d3b\u7684\u9501\u5b9a\u673a\u5236\u3002<code>ReentrantLock<\/code> \u7684\u5b9e\u73b0\u57fa\u4e8e AQS\uff08AbstractQueuedSynchronizer\uff0c\u62bd\u8c61\u961f\u5217\u540c\u6b65\u5668\uff09\uff0c\u8fd9\u662f\u4e00\u4e2a\u7528\u4e8e\u6784\u5efa\u540c\u6b65\u7ec4\u4ef6\u7684\u57fa\u7840\u6846\u67b6\u3002<\/p>\n<h2>ReentrantLock \u7684\u4e3b\u8981\u7279\u6027<\/h2>\n<ol>\n<li><strong>\u53ef\u91cd\u5165\u6027<\/strong>\uff1a\u540c\u4e00\u4e2a\u7ebf\u7a0b\u53ef\u4ee5\u591a\u6b21\u83b7\u53d6\u540c\u4e00\u4e2a\u9501\uff0c\u800c\u4e0d\u4f1a\u5bfc\u81f4\u6b7b\u9501\u3002<\/li>\n<li><strong>\u516c\u5e73\u6027<\/strong>\uff1a\u652f\u6301\u516c\u5e73\u9501\u548c\u975e\u516c\u5e73\u9501\u3002\u516c\u5e73\u9501\u4f1a\u6309\u7167\u7ebf\u7a0b\u8bf7\u6c42\u9501\u7684\u987a\u5e8f\u6765\u5206\u914d\u9501\uff0c\u800c\u975e\u516c\u5e73\u9501\u5219\u5141\u8bb8\u7ebf\u7a0b\u63d2\u961f\u3002<\/li>\n<li><strong>\u6761\u4ef6\u53d8\u91cf<\/strong>\uff1a\u901a\u8fc7 <code>Condition<\/code> \u63a5\u53e3\u63d0\u4f9b\u4e86\u7c7b\u4f3c\u4e8e <code>Object<\/code> \u76d1\u89c6\u5668\u65b9\u6cd5\uff08\u5982 <code>wait<\/code>, <code>notify<\/code>, <code>notifyAll<\/code>\uff09\u7684\u529f\u80fd\u3002<\/li>\n<\/ol>\n<h2>ReentrantLock \u7684\u5b9e\u73b0\u539f\u7406<\/h2>\n<p><code>ReentrantLock<\/code> \u7684\u5b9e\u73b0\u4e3b\u8981\u4f9d\u8d56\u4e8e AQS\uff08AbstractQueuedSynchronizer\uff09\uff0cAQS \u662f\u4e00\u4e2a\u7528\u4e8e\u6784\u5efa\u540c\u6b65\u7ec4\u4ef6\u7684\u57fa\u7840\u6846\u67b6\uff0c\u5b83\u63d0\u4f9b\u4e86\u4ee5\u4e0b\u6838\u5fc3\u529f\u80fd\uff1a<\/p>\n<ul>\n<li><strong>\u72b6\u6001\u7ba1\u7406<\/strong>\uff1a\u901a\u8fc7\u4e00\u4e2a <code>int<\/code> \u7c7b\u578b\u7684 <code>state<\/code> \u5b57\u6bb5\u6765\u8868\u793a\u9501\u7684\u72b6\u6001\u3002<\/li>\n<li><strong>\u7ebf\u7a0b\u6392\u961f<\/strong>\uff1a\u901a\u8fc7\u4e00\u4e2a FIFO \u961f\u5217\u6765\u7ba1\u7406\u7b49\u5f85\u83b7\u53d6\u9501\u7684\u7ebf\u7a0b\u3002<\/li>\n<li><strong>CAS \u64cd\u4f5c<\/strong>\uff1a\u4f7f\u7528 CAS \u64cd\u4f5c\u6765\u5b9e\u73b0\u65e0\u9501\u7684\u540c\u6b65\u673a\u5236\u3002<\/li>\n<\/ul>\n<h3>1. <strong>AQS \u7684\u6838\u5fc3\u7ed3\u6784<\/strong><\/h3>\n<p>AQS \u7684\u6838\u5fc3\u7ed3\u6784\u5305\u62ec\uff1a<\/p>\n<ul>\n<li><strong><code>state<\/code> \u5b57\u6bb5<\/strong>\uff1a\u8868\u793a\u9501\u7684\u72b6\u6001\uff0c0 \u8868\u793a\u9501\u672a\u88ab\u5360\u7528\uff0c\u5927\u4e8e 0 \u8868\u793a\u9501\u88ab\u5360\u7528\u3002<\/li>\n<li><strong><code>exclusiveOwnerThread<\/code> \u5b57\u6bb5<\/strong>\uff1a\u8bb0\u5f55\u5f53\u524d\u6301\u6709\u9501\u7684\u7ebf\u7a0b\u3002<\/li>\n<li><strong>FIFO \u961f\u5217<\/strong>\uff1a\u7528\u4e8e\u7ba1\u7406\u7b49\u5f85\u83b7\u53d6\u9501\u7684\u7ebf\u7a0b\u3002<\/li>\n<\/ul>\n<h3>2. <strong>ReentrantLock \u7684\u5b9e\u73b0<\/strong><\/h3>\n<p><code>ReentrantLock<\/code> \u5185\u90e8\u7ef4\u62a4\u4e86\u4e00\u4e2a <code>Sync<\/code> \u5bf9\u8c61\uff0c<code>Sync<\/code> \u662f AQS \u7684\u5b50\u7c7b\uff0c\u7528\u4e8e\u5b9e\u73b0\u5177\u4f53\u7684\u9501\u903b\u8f91\u3002<code>ReentrantLock<\/code> \u6709\u4e24\u4e2a\u5185\u90e8\u7c7b\uff1a<\/p>\n<ul>\n<li><strong><code>NonfairSync<\/code><\/strong>\uff1a\u975e\u516c\u5e73\u9501\u7684\u5b9e\u73b0\u3002<\/li>\n<li><strong><code>FairSync<\/code><\/strong>\uff1a\u516c\u5e73\u9501\u7684\u5b9e\u73b0\u3002<\/li>\n<\/ul>\n<h4>2.1 <strong>\u975e\u516c\u5e73\u9501\u7684\u5b9e\u73b0<\/strong><\/h4>\n<p>\u975e\u516c\u5e73\u9501\u5141\u8bb8\u7ebf\u7a0b\u5728\u83b7\u53d6\u9501\u65f6\u63d2\u961f\uff0c\u5373\u7ebf\u7a0b\u53ef\u4ee5\u76f4\u63a5\u5c1d\u8bd5\u83b7\u53d6\u9501\uff0c\u800c\u4e0d\u8003\u8651\u5176\u4ed6\u7b49\u5f85\u7ebf\u7a0b\u7684\u987a\u5e8f\u3002<\/p>\n<pre><code class=\"language-java\">final void lock() {\n    if (compareAndSetState(0, 1))\n        setExclusiveOwnerThread(Thread.currentThread());\n    else\n        acquire(1);\n}<\/code><\/pre>\n<ul>\n<li><strong><code>compareAndSetState(0, 1)<\/code><\/strong>\uff1a\u4f7f\u7528 CAS \u64cd\u4f5c\u5c1d\u8bd5\u5c06 <code>state<\/code> \u4ece 0 \u66f4\u65b0\u4e3a 1\uff0c\u8868\u793a\u83b7\u53d6\u9501\u3002<\/li>\n<li><strong><code>setExclusiveOwnerThread(Thread.currentThread())<\/code><\/strong>\uff1a\u5982\u679c CAS \u64cd\u4f5c\u6210\u529f\uff0c\u5219\u8bbe\u7f6e\u5f53\u524d\u7ebf\u7a0b\u4e3a\u9501\u7684\u6301\u6709\u8005\u3002<\/li>\n<li><strong><code>acquire(1)<\/code><\/strong>\uff1a\u5982\u679c CAS \u64cd\u4f5c\u5931\u8d25\uff0c\u5219\u8c03\u7528 AQS \u7684 <code>acquire<\/code> \u65b9\u6cd5\uff0c\u8fdb\u5165\u7b49\u5f85\u961f\u5217\u3002<\/li>\n<\/ul>\n<h4>2.2 <strong>\u516c\u5e73\u9501\u7684\u5b9e\u73b0<\/strong><\/h4>\n<p>\u516c\u5e73\u9501\u4f1a\u6309\u7167\u7ebf\u7a0b\u8bf7\u6c42\u9501\u7684\u987a\u5e8f\u6765\u5206\u914d\u9501\uff0c\u5373\u5148\u8bf7\u6c42\u7684\u7ebf\u7a0b\u5148\u83b7\u5f97\u9501\u3002<\/p>\n<pre><code class=\"language-java\">final void lock() {\n    acquire(1);\n}<\/code><\/pre>\n<ul>\n<li><strong><code>acquire(1)<\/code><\/strong>\uff1a\u76f4\u63a5\u8c03\u7528 AQS \u7684 <code>acquire<\/code> \u65b9\u6cd5\uff0c\u8fdb\u5165\u7b49\u5f85\u961f\u5217\uff0c\u6309\u7167 FIFO \u987a\u5e8f\u83b7\u53d6\u9501\u3002<\/li>\n<\/ul>\n<h4>2.3 <strong>\u91ca\u653e\u9501<\/strong><\/h4>\n<p>\u65e0\u8bba\u662f\u516c\u5e73\u9501\u8fd8\u662f\u975e\u516c\u5e73\u9501\uff0c\u91ca\u653e\u9501\u7684\u903b\u8f91\u90fd\u662f\u76f8\u540c\u7684\u3002<\/p>\n<pre><code class=\"language-java\">public void unlock() {\n    sync.release(1);\n}<\/code><\/pre>\n<ul>\n<li><strong><code>release(1)<\/code><\/strong>\uff1a\u8c03\u7528 AQS \u7684 <code>release<\/code> \u65b9\u6cd5\uff0c\u91ca\u653e\u9501\u3002<\/li>\n<\/ul>\n<h3>3. <strong>\u6761\u4ef6\u53d8\u91cf\uff08Condition\uff09<\/strong><\/h3>\n<p><code>ReentrantLock<\/code> \u901a\u8fc7 <code>newCondition()<\/code> \u65b9\u6cd5\u521b\u5efa <code>Condition<\/code> \u5bf9\u8c61\uff0c<code>Condition<\/code> \u63d0\u4f9b\u4e86\u7c7b\u4f3c\u4e8e <code>Object<\/code> \u76d1\u89c6\u5668\u65b9\u6cd5\u7684\u529f\u80fd\u3002<\/p>\n<pre><code class=\"language-java\">Condition condition = lock.newCondition();<\/code><\/pre>\n<ul>\n<li><strong><code>await()<\/code><\/strong>\uff1a\u4f7f\u5f53\u524d\u7ebf\u7a0b\u7b49\u5f85\uff0c\u5e76\u91ca\u653e\u9501\u3002<\/li>\n<li><strong><code>signal()<\/code><\/strong>\uff1a\u5524\u9192\u4e00\u4e2a\u7b49\u5f85\u7684\u7ebf\u7a0b\u3002<\/li>\n<li><strong><code>signalAll()<\/code><\/strong>\uff1a\u5524\u9192\u6240\u6709\u7b49\u5f85\u7684\u7ebf\u7a0b\u3002<\/li>\n<\/ul>\n<h1>b \u6811\u548c b+ \u6811<\/h1>\n<h2>1. <strong>\u6570\u636e\u5b58\u50a8<\/strong><\/h2>\n<ul>\n<li><strong>B \u6811<\/strong> \uff1a\u5185\u90e8\u8282\u70b9\u548c\u53f6\u5b50\u8282\u70b9\u90fd\u53ef\u4ee5\u5b58\u50a8\u6570\u636e\u3002<\/li>\n<li><strong>B+ \u6811<\/strong> \uff1a\u53ea\u6709\u53f6\u5b50\u8282\u70b9\u5b58\u50a8\u6570\u636e\uff0c\u5185\u90e8\u8282\u70b9\u53ea\u5b58\u50a8\u952e\u503c\u3002<\/li>\n<\/ul>\n<h2>2. <strong>\u8303\u56f4\u67e5\u8be2<\/strong><\/h2>\n<ul>\n<li><strong>B \u6811<\/strong> \uff1a\u8303\u56f4\u67e5\u8be2\u9700\u8981\u904d\u5386\u591a\u4e2a\u8282\u70b9\uff0c\u6548\u7387\u8f83\u4f4e\u3002<\/li>\n<li><strong>B+ \u6811<\/strong> \uff1a\u6240\u6709\u53f6\u5b50\u8282\u70b9\u901a\u8fc7\u94fe\u8868\u8fde\u63a5\uff0c\u4fbf\u4e8e\u8303\u56f4\u67e5\u8be2\u3002<\/li>\n<\/ul>\n<h2>3. <strong>\u78c1\u76d8 I\/O \u6548\u7387<\/strong><\/h2>\n<ul>\n<li><strong>B \u6811<\/strong> \uff1a\u6bcf\u6b21\u67e5\u627e\u53ef\u80fd\u9700\u8981\u8bbf\u95ee\u591a\u4e2a\u8282\u70b9\uff0c\u78c1\u76d8 I\/O \u6b21\u6570\u8f83\u591a\u3002<\/li>\n<li><strong>B+ \u6811<\/strong> \uff1a\u6240\u6709\u6570\u636e\u5b58\u50a8\u5728\u53f6\u5b50\u8282\u70b9\uff0c\u67e5\u627e\u64cd\u4f5c\u901a\u5e38\u53ea\u9700\u8981\u8bbf\u95ee\u4e00\u4e2a\u8282\u70b9\uff0c\u78c1\u76d8 I\/O \u6b21\u6570\u8f83\u5c11\u3002<\/li>\n<\/ul>\n<h2>4. <strong>\u7a7a\u95f4\u5229\u7528\u7387<\/strong><\/h2>\n<ul>\n<li><strong>B \u6811<\/strong> \uff1a\u5185\u90e8\u8282\u70b9\u548c\u53f6\u5b50\u8282\u70b9\u90fd\u53ef\u4ee5\u5b58\u50a8\u6570\u636e\uff0c\u7a7a\u95f4\u5229\u7528\u7387\u8f83\u9ad8\u3002<\/li>\n<li><strong>B+ \u6811<\/strong> \uff1a\u5185\u90e8\u8282\u70b9\u53ea\u5b58\u50a8\u952e\u503c\uff0c\u7a7a\u95f4\u5229\u7528\u7387\u8f83\u4f4e\u3002<\/li>\n<\/ul>\n<h1>\u5bf9\u8c61\u7684\u521b\u5efa\u8fc7\u7a0b<\/h1>\n<p>\u5728 Java \u4e2d\uff0c\u5bf9\u8c61\u7684\u521b\u5efa\u8fc7\u7a0b\u6d89\u53ca\u591a\u4e2a\u6b65\u9aa4\uff0c\u5305\u62ec\u7c7b\u52a0\u8f7d\u3001\u5185\u5b58\u5206\u914d\u3001\u521d\u59cb\u5316\u7b49\u3002\u4ee5\u4e0b\u662f Java \u5bf9\u8c61\u521b\u5efa\u8fc7\u7a0b\u7684\u8be6\u7ec6\u6b65\u9aa4\uff1a<\/p>\n<h2>1. <strong>\u7c7b\u52a0\u8f7d<\/strong><\/h2>\n<p>\u5728\u521b\u5efa\u5bf9\u8c61\u4e4b\u524d\uff0cJava \u865a\u62df\u673a\uff08JVM\uff09\u9700\u8981\u786e\u4fdd\u5bf9\u8c61\u6240\u5c5e\u7684\u7c7b\u5df2\u7ecf\u88ab\u52a0\u8f7d\u5230\u5185\u5b58\u4e2d\u3002\u7c7b\u52a0\u8f7d\u8fc7\u7a0b\u5305\u62ec\u4ee5\u4e0b\u51e0\u4e2a\u9636\u6bb5\uff1a<\/p>\n<ul>\n<li><strong>\u52a0\u8f7d\uff08Loading\uff09<\/strong>\uff1aJVM \u901a\u8fc7\u7c7b\u52a0\u8f7d\u5668\uff08ClassLoader\uff09\u5c06\u7c7b\u7684\u5b57\u8282\u7801\u52a0\u8f7d\u5230\u5185\u5b58\u4e2d\u3002<\/li>\n<li><strong>\u94fe\u63a5\uff08Linking\uff09<\/strong>\uff1a\u94fe\u63a5\u8fc7\u7a0b\u5305\u62ec\u4ee5\u4e0b\u4e09\u4e2a\u5b50\u9636\u6bb5\uff1a\n<ul>\n<li><strong>\u9a8c\u8bc1\uff08Verification\uff09<\/strong>\uff1a\u786e\u4fdd\u5b57\u8282\u7801\u7684\u6b63\u786e\u6027\u548c\u5b89\u5168\u6027\u3002<\/li>\n<li><strong>\u51c6\u5907\uff08Preparation\uff09<\/strong>\uff1a\u4e3a\u7c7b\u7684\u9759\u6001\u53d8\u91cf\u5206\u914d\u5185\u5b58\uff0c\u5e76\u8bbe\u7f6e\u9ed8\u8ba4\u521d\u59cb\u503c\u3002<\/li>\n<li><strong>\u89e3\u6790\uff08Resolution\uff09<\/strong>\uff1a\u5c06\u7c7b\u3001\u63a5\u53e3\u3001\u5b57\u6bb5\u548c\u65b9\u6cd5\u7684\u7b26\u53f7\u5f15\u7528\u89e3\u6790\u4e3a\u76f4\u63a5\u5f15\u7528\u3002<\/li>\n<\/ul>\n<\/li>\n<li><strong>\u521d\u59cb\u5316\uff08Initialization\uff09<\/strong>\uff1a\u6267\u884c\u7c7b\u7684\u9759\u6001\u521d\u59cb\u5316\u5757\u548c\u9759\u6001\u53d8\u91cf\u7684\u8d4b\u503c\u64cd\u4f5c\u3002<\/li>\n<\/ul>\n<h2>2. <strong>\u5206\u914d\u5185\u5b58<\/strong><\/h2>\n<p>\u4e00\u65e6\u7c7b\u88ab\u52a0\u8f7d\u5e76\u521d\u59cb\u5316\uff0cJVM \u5c31\u4f1a\u4e3a\u65b0\u5bf9\u8c61\u5206\u914d\u5185\u5b58\u3002\u5185\u5b58\u5206\u914d\u7684\u65b9\u5f0f\u53d6\u51b3\u4e8e\u5bf9\u8c61\u7684\u7c7b\u578b\u548c JVM \u7684\u5b9e\u73b0\uff1a<\/p>\n<ul>\n<li><strong>\u5806\u5185\u5b58<\/strong>\uff1a\u5927\u591a\u6570\u5bf9\u8c61\u7684\u5185\u5b58\u5206\u914d\u5728\u5806\uff08Heap\uff09\u4e2d\u3002\u5806\u662f JVM \u7ba1\u7406\u7684\u5185\u5b58\u533a\u57df\uff0c\u7528\u4e8e\u5b58\u50a8\u52a8\u6001\u5206\u914d\u7684\u5bf9\u8c61\u3002<\/li>\n<li><strong>\u6808\u5185\u5b58<\/strong>\uff1a\u5bf9\u4e8e\u5c40\u90e8\u53d8\u91cf\u548c\u65b9\u6cd5\u53c2\u6570\uff0c\u5185\u5b58\u5206\u914d\u5728\u6808\uff08Stack\uff09\u4e2d\u3002\u6808\u5185\u5b58\u7684\u751f\u547d\u5468\u671f\u4e0e\u65b9\u6cd5\u7684\u8c03\u7528\u5468\u671f\u4e00\u81f4\u3002<\/li>\n<\/ul>\n<h2>3. <strong>\u521d\u59cb\u5316\u5bf9\u8c61<\/strong><\/h2>\n<p>\u5185\u5b58\u5206\u914d\u5b8c\u6210\u540e\uff0cJVM \u4f1a\u5bf9\u5bf9\u8c61\u8fdb\u884c\u521d\u59cb\u5316\u3002\u521d\u59cb\u5316\u8fc7\u7a0b\u5305\u62ec\u4ee5\u4e0b\u51e0\u4e2a\u6b65\u9aa4\uff1a<\/p>\n<ul>\n<li><strong>\u9ed8\u8ba4\u521d\u59cb\u5316<\/strong>\uff1aJVM \u4f1a\u4e3a\u5bf9\u8c61\u7684\u5b57\u6bb5\u8bbe\u7f6e\u9ed8\u8ba4\u503c\uff08\u5982 <code>int<\/code> \u4e3a 0\uff0c<code>boolean<\/code> \u4e3a <code>false<\/code>\uff0c\u5f15\u7528\u7c7b\u578b\u4e3a <code>null<\/code>\uff09\u3002<\/li>\n<li><strong>\u663e\u5f0f\u521d\u59cb\u5316<\/strong>\uff1a\u6267\u884c\u5bf9\u8c61\u7684\u6784\u9020\u5668\uff08Constructor\uff09\uff0c\u4e3a\u5bf9\u8c61\u7684\u5b57\u6bb5\u8d4b\u503c\u3002\u6784\u9020\u5668\u662f\u7c7b\u4e2d\u7528\u4e8e\u521d\u59cb\u5316\u5bf9\u8c61\u7684\u7279\u6b8a\u65b9\u6cd5\u3002<\/li>\n<\/ul>\n<h2>4. <strong>\u6267\u884c\u6784\u9020\u5668<\/strong><\/h2>\n<p>\u6784\u9020\u5668\u662f\u5bf9\u8c61\u521d\u59cb\u5316\u7684\u6838\u5fc3\u90e8\u5206\uff0c\u5b83\u8d1f\u8d23\u4e3a\u5bf9\u8c61\u7684\u5b57\u6bb5\u8d4b\u503c\uff0c\u5e76\u6267\u884c\u5fc5\u8981\u7684\u521d\u59cb\u5316\u903b\u8f91\u3002\u6784\u9020\u5668\u7684\u6267\u884c\u8fc7\u7a0b\u5305\u62ec\u4ee5\u4e0b\u51e0\u4e2a\u6b65\u9aa4\uff1a<\/p>\n<ul>\n<li><strong>\u9690\u5f0f\u8c03\u7528\u7236\u7c7b\u6784\u9020\u5668<\/strong>\uff1a\u5982\u679c\u7c7b\u7ee7\u627f\u81ea\u7236\u7c7b\uff0cJVM \u4f1a\u9996\u5148\u8c03\u7528\u7236\u7c7b\u7684\u6784\u9020\u5668\u3002\u8fd9\u4e2a\u8fc7\u7a0b\u4f1a\u9012\u5f52\u5730\u8c03\u7528\u7236\u7c7b\u7684\u6784\u9020\u5668\uff0c\u76f4\u5230 <code>Object<\/code> \u7c7b\u3002<\/li>\n<li><strong>\u6267\u884c\u5b9e\u4f8b\u521d\u59cb\u5316\u5757<\/strong>\uff1a\u5728\u8c03\u7528\u6784\u9020\u5668\u4e4b\u524d\uff0cJVM \u4f1a\u6267\u884c\u7c7b\u7684\u5b9e\u4f8b\u521d\u59cb\u5316\u5757\uff08\u5982\u679c\u6709\u7684\u8bdd\uff09\u3002\u5b9e\u4f8b\u521d\u59cb\u5316\u5757\u662f\u7c7b\u4e2d\u7528\u4e8e\u521d\u59cb\u5316\u5bf9\u8c61\u7684\u4ee3\u7801\u5757\u3002<\/li>\n<li><strong>\u6267\u884c\u6784\u9020\u5668\u4ee3\u7801<\/strong>\uff1a\u6700\u540e\uff0cJVM \u6267\u884c\u5f53\u524d\u7c7b\u7684\u6784\u9020\u5668\u4ee3\u7801\uff0c\u5b8c\u6210\u5bf9\u8c61\u7684\u521d\u59cb\u5316\u3002<\/li>\n<\/ul>\n<h2>5. <strong>\u8fd4\u56de\u5bf9\u8c61\u5f15\u7528<\/strong><\/h2>\n<p>\u5bf9\u8c61\u521d\u59cb\u5316\u5b8c\u6210\u540e\uff0cJVM \u4f1a\u8fd4\u56de\u5bf9\u8c61\u7684\u5f15\u7528\uff0c\u5e76\u5c06\u5176\u8d4b\u503c\u7ed9\u53d8\u91cf\u3002\u6b64\u65f6\uff0c\u5bf9\u8c61\u5df2\u7ecf\u5b8c\u5168\u521b\u5efa\u5e76\u53ef\u4ee5\u4f7f\u7528\u4e86\u3002<\/p>\n<h2>\u793a\u4f8b\u4ee3\u7801<\/h2>\n<p>\u4ee5\u4e0b\u662f\u4e00\u4e2a\u7b80\u5355\u7684 Java \u7c7b\uff0c\u5c55\u793a\u4e86\u5bf9\u8c61\u7684\u521b\u5efa\u8fc7\u7a0b\uff1a<\/p>\n<pre><code class=\"language-java\">public class MyClass {\n    \/\/ \u9759\u6001\u521d\u59cb\u5316\u5757\n    static {\n        System.out.println(&quot;Static initialization block&quot;);\n    }\n\n    \/\/ \u5b9e\u4f8b\u53d8\u91cf\n    private int value;\n\n    \/\/ \u5b9e\u4f8b\u521d\u59cb\u5316\u5757\n    {\n        System.out.println(&quot;Instance initialization block&quot;);\n        value = 10;\n    }\n\n    \/\/ \u6784\u9020\u5668\n    public MyClass() {\n        System.out.println(&quot;Constructor called&quot;);\n    }\n\n    public static void main(String[] args) {\n        System.out.println(&quot;Creating object...&quot;);\n        MyClass obj = new MyClass();\n        System.out.println(&quot;Object created: &quot; + obj);\n    }\n}<\/code><\/pre>\n<h2>\u8f93\u51fa\u7ed3\u679c<\/h2>\n<pre><code>Static initialization block\nCreating object...\nInstance initialization block\nConstructor called\nObject created: MyClass@1b6d3586<\/code><\/pre>\n<h1>\u4e8b\u52a1\u7684\u9694\u79bb\u7ea7\u522b<\/h1>\n<h2>1. <strong>\u8bfb\u672a\u63d0\u4ea4\uff08Read Uncommitted\uff09<\/strong><\/h2>\n<ul>\n<li><strong>\u5b9a\u4e49<\/strong>\uff1a\u4e8b\u52a1\u53ef\u4ee5\u8bfb\u53d6\u5176\u4ed6\u4e8b\u52a1\u5c1a\u672a\u63d0\u4ea4\u7684\u6570\u636e\u3002<\/li>\n<li><strong>\u95ee\u9898<\/strong>\uff1a\u53ef\u80fd\u51fa\u73b0\u810f\u8bfb\uff08Dirty Read\uff09\u3002\n<ul>\n<li><strong>\u810f\u8bfb<\/strong>\uff1a\u4e00\u4e2a\u4e8b\u52a1\u8bfb\u53d6\u4e86\u53e6\u4e00\u4e2a\u4e8b\u52a1\u5c1a\u672a\u63d0\u4ea4\u7684\u6570\u636e\uff0c\u5982\u679c\u8be5\u4e8b\u52a1\u56de\u6eda\uff0c\u8bfb\u53d6\u7684\u6570\u636e\u5c06\u662f\u65e0\u6548\u7684\u3002<\/li>\n<\/ul>\n<\/li>\n<li><strong>\u9002\u7528\u573a\u666f<\/strong>\uff1a\u6781\u5c11\u4f7f\u7528\uff0c\u901a\u5e38\u53ea\u5728\u6027\u80fd\u8981\u6c42\u6781\u9ad8\u4e14\u5bf9\u6570\u636e\u4e00\u81f4\u6027\u8981\u6c42\u8f83\u4f4e\u7684\u573a\u666f\u4e2d\u4f7f\u7528\u3002<\/li>\n<\/ul>\n<h2>2. <strong>\u8bfb\u5df2\u63d0\u4ea4\uff08Read Committed\uff09<\/strong><\/h2>\n<ul>\n<li><strong>\u5b9a\u4e49<\/strong>\uff1a\u4e8b\u52a1\u53ea\u80fd\u8bfb\u53d6\u5176\u4ed6\u4e8b\u52a1\u5df2\u7ecf\u63d0\u4ea4\u7684\u6570\u636e\u3002<\/li>\n<li><strong>\u95ee\u9898<\/strong>\uff1a\u53ef\u80fd\u51fa\u73b0\u4e0d\u53ef\u91cd\u590d\u8bfb\uff08Non-Repeatable Read\uff09\u3002\n<ul>\n<li><strong>\u4e0d\u53ef\u91cd\u590d\u8bfb<\/strong>\uff1a\u4e00\u4e2a\u4e8b\u52a1\u5728\u540c\u4e00\u4e2a\u4e8b\u52a1\u4e2d\u591a\u6b21\u8bfb\u53d6\u540c\u4e00\u6570\u636e\uff0c\u4f46\u5728\u4e24\u6b21\u8bfb\u53d6\u4e4b\u95f4\uff0c\u53e6\u4e00\u4e2a\u4e8b\u52a1\u4fee\u6539\u4e86\u8be5\u6570\u636e\u5e76\u63d0\u4ea4\uff0c\u5bfc\u81f4\u4e24\u6b21\u8bfb\u53d6\u7684\u7ed3\u679c\u4e0d\u4e00\u81f4\u3002<\/li>\n<\/ul>\n<\/li>\n<li><strong>\u9002\u7528\u573a\u666f<\/strong>\uff1a\u5927\u591a\u6570\u6570\u636e\u5e93\u7cfb\u7edf\u7684\u9ed8\u8ba4\u9694\u79bb\u7ea7\u522b\uff0c\u9002\u7528\u4e8e\u5927\u591a\u6570\u4e1a\u52a1\u573a\u666f\u3002<\/li>\n<\/ul>\n<h2>3. <strong>\u53ef\u91cd\u590d\u8bfb\uff08Repeatable Read\uff09<\/strong><\/h2>\n<ul>\n<li><strong>\u5b9a\u4e49<\/strong>\uff1a\u4e8b\u52a1\u5728\u540c\u4e00\u4e2a\u4e8b\u52a1\u4e2d\u591a\u6b21\u8bfb\u53d6\u540c\u4e00\u6570\u636e\u65f6\uff0c\u4fdd\u8bc1\u8bfb\u53d6\u7ed3\u679c\u4e00\u81f4\u3002<\/li>\n<li><strong>\u95ee\u9898<\/strong>\uff1a\u53ef\u80fd\u51fa\u73b0\u5e7b\u8bfb\uff08Phantom Read\uff09\u3002\n<ul>\n<li><strong>\u5e7b\u8bfb<\/strong>\uff1a\u4e00\u4e2a\u4e8b\u52a1\u5728\u540c\u4e00\u4e2a\u4e8b\u52a1\u4e2d\u591a\u6b21\u6267\u884c\u540c\u4e00\u67e5\u8be2\uff0c\u4f46\u5728\u4e24\u6b21\u67e5\u8be2\u4e4b\u95f4\uff0c\u53e6\u4e00\u4e2a\u4e8b\u52a1\u63d2\u5165\u4e86\u65b0\u7684\u6570\u636e\u5e76\u63d0\u4ea4\uff0c\u5bfc\u81f4\u4e24\u6b21\u67e5\u8be2\u7684\u7ed3\u679c\u96c6\u4e0d\u4e00\u81f4\u3002<\/li>\n<\/ul>\n<\/li>\n<li><strong>\u9002\u7528\u573a\u666f<\/strong>\uff1a\u9002\u7528\u4e8e\u9700\u8981\u4fdd\u8bc1\u6570\u636e\u4e00\u81f4\u6027\u7684\u573a\u666f\uff0c\u4f46\u53ef\u80fd\u4f1a\u5e26\u6765\u8f83\u9ad8\u7684\u9501\u5f00\u9500\u3002<\/li>\n<\/ul>\n<h2>4. <strong>\u4e32\u884c\u5316\uff08Serializable\uff09<\/strong><\/h2>\n<ul>\n<li><strong>\u5b9a\u4e49<\/strong>\uff1a\u4e8b\u52a1\u5b8c\u5168\u9694\u79bb\uff0c\u6bcf\u4e2a\u4e8b\u52a1\u6309\u987a\u5e8f\u6267\u884c\uff0c\u5c31\u50cf\u6240\u6709\u4e8b\u52a1\u90fd\u662f\u4e32\u884c\u6267\u884c\u7684\u4e00\u6837\u3002<\/li>\n<li><strong>\u95ee\u9898<\/strong>\uff1a\u6027\u80fd\u6700\u4f4e\uff0c\u53ef\u80fd\u5bfc\u81f4\u5927\u91cf\u7684\u9501\u7b49\u5f85\u548c\u6b7b\u9501\u3002\n<ul>\n<li><strong>\u9501\u7b49\u5f85<\/strong>\uff1a\u4e8b\u52a1\u9700\u8981\u7b49\u5f85\u5176\u4ed6\u4e8b\u52a1\u91ca\u653e\u9501\u3002<\/li>\n<li><strong>\u6b7b\u9501<\/strong>\uff1a\u4e24\u4e2a\u6216\u591a\u4e2a\u4e8b\u52a1\u4e92\u76f8\u7b49\u5f85\u5bf9\u65b9\u91ca\u653e\u9501\uff0c\u5bfc\u81f4\u6240\u6709\u4e8b\u52a1\u90fd\u65e0\u6cd5\u7ee7\u7eed\u6267\u884c\u3002<\/li>\n<\/ul>\n<\/li>\n<li><strong>\u9002\u7528\u573a\u666f<\/strong>\uff1a\u9002\u7528\u4e8e\u5bf9\u6570\u636e\u4e00\u81f4\u6027\u8981\u6c42\u6781\u9ad8\u7684\u573a\u666f\uff0c\u4f46\u901a\u5e38\u4f1a\u5e26\u6765\u8f83\u9ad8\u7684\u6027\u80fd\u5f00\u9500\u3002<\/li>\n<\/ul>\n<h2>\u9694\u79bb\u7ea7\u522b\u4e0e\u5e76\u53d1\u95ee\u9898<\/h2>\n<table>\n<thead>\n<tr>\n<th>\u9694\u79bb\u7ea7\u522b<\/th>\n<th>\u810f\u8bfb<\/th>\n<th>\u4e0d\u53ef\u91cd\u590d\u8bfb<\/th>\n<th>\u5e7b\u8bfb<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>\u8bfb\u672a\u63d0\u4ea4<\/td>\n<td>\u53ef\u80fd<\/td>\n<td>\u53ef\u80fd<\/td>\n<td>\u53ef\u80fd<\/td>\n<\/tr>\n<tr>\n<td>\u8bfb\u5df2\u63d0\u4ea4<\/td>\n<td>\u4e0d\u53ef\u80fd<\/td>\n<td>\u53ef\u80fd<\/td>\n<td>\u53ef\u80fd<\/td>\n<\/tr>\n<tr>\n<td>\u53ef\u91cd\u590d\u8bfb<\/td>\n<td>\u4e0d\u53ef\u80fd<\/td>\n<td>\u4e0d\u53ef\u80fd<\/td>\n<td>\u53ef\u80fd(innodb\u4e0d\u53ef\u80fd)<\/td>\n<\/tr>\n<tr>\n<td>\u4e32\u884c\u5316<\/td>\n<td>\u4e0d\u53ef\u80fd<\/td>\n<td>\u4e0d\u53ef\u80fd<\/td>\n<td>\u4e0d\u53ef\u80fd<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<div  class='collapse-block shadow-sm collapse-block-danger collapsed hide-border-left'><div class='collapse-block-title'><span class='collapse-block-title-inner'>InnoDB\u4e0d\u53ef\u80fd\u7684\u539f\u56e0<\/span><i class='collapse-icon fa fa-angle-down'><\/i><\/div><div class='collapse-block-body' style='display:none;'><\/p>\n<p>\u5728 InnoDB \u5b58\u50a8\u5f15\u64ce\u4e2d\uff0c\u867d\u7136\u9ed8\u8ba4\u7684\u4e8b\u52a1\u9694\u79bb\u7ea7\u522b\u662f <code>REPEATABLE READ<\/code>\uff0c\u4f46\u5b83\u901a\u8fc7\u4e00\u4e9b\u7279\u6b8a\u7684\u673a\u5236\u907f\u514d\u4e86\u5e7b\u8bfb\uff08Phantom Read\uff09\u95ee\u9898\u3002\u4ee5\u4e0b\u662f InnoDB \u5982\u4f55\u907f\u514d\u5e7b\u8bfb\u7684\u8be6\u7ec6\u89e3\u91ca\uff1a<\/p>\n<h3>1. <strong>Next-Key Locking\uff08\u95f4\u9699\u9501\uff09<\/strong><\/h3>\n<p>InnoDB \u4f7f\u7528\u4e86\u4e00\u79cd\u79f0\u4e3a <strong>Next-Key Locking<\/strong> \u7684\u9501\u673a\u5236\uff0c\u5b83\u7ed3\u5408\u4e86\u884c\u9501\uff08Record Lock\uff09\u548c\u95f4\u9699\u9501\uff08Gap Lock\uff09\u3002Next-Key Locking \u4e0d\u4ec5\u9501\u4f4f\u67e5\u8be2\u5230\u7684\u884c\uff0c\u8fd8\u9501\u4f4f\u8fd9\u4e9b\u884c\u4e4b\u95f4\u7684\u95f4\u9699\uff0c\u4ece\u800c\u9632\u6b62\u5176\u4ed6\u4e8b\u52a1\u5728\u8fd9\u4e9b\u95f4\u9699\u4e2d\u63d2\u5165\u65b0\u7684\u884c\u3002<\/p>\n<h4>1.1 <strong>\u884c\u9501\uff08Record Lock\uff09<\/strong><\/h4>\n<ul>\n<li><strong>\u884c\u9501<\/strong>\uff1a\u9501\u4f4f\u67e5\u8be2\u5230\u7684\u5177\u4f53\u884c\uff0c\u9632\u6b62\u5176\u4ed6\u4e8b\u52a1\u4fee\u6539\u8fd9\u4e9b\u884c\u3002<\/li>\n<\/ul>\n<h4>1.2 <strong>\u95f4\u9699\u9501\uff08Gap Lock\uff09<\/strong><\/h4>\n<ul>\n<li><strong>\u95f4\u9699\u9501<\/strong>\uff1a\u9501\u4f4f\u67e5\u8be2\u5230\u7684\u884c\u4e4b\u95f4\u7684\u95f4\u9699\uff0c\u9632\u6b62\u5176\u4ed6\u4e8b\u52a1\u5728\u8fd9\u4e9b\u95f4\u9699\u4e2d\u63d2\u5165\u65b0\u7684\u884c\u3002<\/li>\n<\/ul>\n<h4>1.3 <strong>Next-Key Lock<\/strong><\/h4>\n<ul>\n<li><strong>Next-Key Lock<\/strong>\uff1a\u884c\u9501\u548c\u95f4\u9699\u9501\u7684\u7ed3\u5408\uff0c\u9501\u4f4f\u67e5\u8be2\u5230\u7684\u884c\u53ca\u5176\u4e4b\u95f4\u7684\u95f4\u9699\u3002<\/li>\n<\/ul>\n<h3>2. <strong>MVCC\uff08\u591a\u7248\u672c\u5e76\u53d1\u63a7\u5236\uff09<\/strong><\/h3>\n<p>InnoDB \u901a\u8fc7 MVCC \u673a\u5236\u5b9e\u73b0\u4e86 <code>REPEATABLE READ<\/code> \u9694\u79bb\u7ea7\u522b\u3002MVCC \u5141\u8bb8\u591a\u4e2a\u4e8b\u52a1\u540c\u65f6\u8bfb\u53d6\u6570\u636e\u5e93\u7684\u4e0d\u540c\u7248\u672c\uff0c\u4ece\u800c\u907f\u514d\u4e86\u8bfb\u53d6\u672a\u63d0\u4ea4\u6570\u636e\u7684\u95ee\u9898\u3002<\/p>\n<h4>2.1 <strong>Read View<\/strong><\/h4>\n<ul>\n<li><strong>Read View<\/strong>\uff1a\u6bcf\u4e2a\u4e8b\u52a1\u5728\u5f00\u59cb\u65f6\u4f1a\u521b\u5efa\u4e00\u4e2a Read View\uff0c\u5176\u4e2d\u5305\u542b\u4e86\u5f53\u524d\u6d3b\u8dc3\u4e8b\u52a1\u7684\u5217\u8868\u3002\u5f53\u4e8b\u52a1\u8bfb\u53d6\u6570\u636e\u65f6\uff0cInnoDB \u4f1a\u6839\u636e\u8fd9\u4e2a Read View \u6765\u5224\u65ad\u54ea\u4e9b\u6570\u636e\u7248\u672c\u662f\u53ef\u89c1\u7684\u3002<\/li>\n<\/ul>\n<h4>2.2 <strong>\u5feb\u7167\u8bfb\uff08Snapshot Read\uff09<\/strong><\/h4>\n<ul>\n<li><strong>\u5feb\u7167\u8bfb<\/strong>\uff1a\u4e8b\u52a1\u5728\u8bfb\u53d6\u6570\u636e\u65f6\uff0c\u4f7f\u7528\u7684\u662f\u4e8b\u52a1\u5f00\u59cb\u65f6\u7684\u5feb\u7167\uff0c\u5373\u8bfb\u53d6\u7684\u662f\u4e8b\u52a1\u5f00\u59cb\u65f6\u7684\u6570\u636e\u7248\u672c\u3002<\/li>\n<\/ul>\n<h3>3. <strong>\u793a\u4f8b\u8bf4\u660e<\/strong><\/h3>\n<p>\u5047\u8bbe\u6709\u4e00\u4e2a\u8868 <code>accounts<\/code>\uff0c\u5176\u4e2d\u6709\u4e24\u884c\u6570\u636e\uff1a<\/p>\n<table>\n<thead>\n<tr>\n<th>id<\/th>\n<th>balance<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>1<\/td>\n<td>100<\/td>\n<\/tr>\n<tr>\n<td>3<\/td>\n<td>200<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>\u5728\u4e00\u4e2a\u4e8b\u52a1\u4e2d\u6267\u884c\u4ee5\u4e0b\u67e5\u8be2\uff1a<\/p>\n<pre><code>SELECT * FROM accounts WHERE id > 1 AND id &lt; 3;\r\n<\/code><\/pre>\n<p>\u5728 <code>REPEATABLE READ<\/code> \u9694\u79bb\u7ea7\u522b\u4e0b\uff0cInnoDB \u4f1a\u4f7f\u7528 Next-Key Locking \u673a\u5236\uff1a<\/p>\n<ul>\n<li><strong>\u884c\u9501<\/strong>\uff1a\u9501\u4f4f <code>id = 2<\/code> \u7684\u884c\uff08\u5982\u679c\u5b58\u5728\uff09\u3002<\/li>\n<li><strong>\u95f4\u9699\u9501<\/strong>\uff1a\u9501\u4f4f <code>id = 1<\/code> \u548c <code>id = 3<\/code> \u4e4b\u95f4\u7684\u95f4\u9699\uff0c\u9632\u6b62\u5176\u4ed6\u4e8b\u52a1\u63d2\u5165\u65b0\u7684\u884c\u3002<\/li>\n<\/ul>\n<p>\u56e0\u6b64\uff0c\u5373\u4f7f\u5176\u4ed6\u4e8b\u52a1\u8bd5\u56fe\u63d2\u5165 <code>id = 2<\/code> \u7684\u884c\uff0c\u4e5f\u4f1a\u88ab\u95f4\u9699\u9501\u963b\u585e\uff0c\u4ece\u800c\u907f\u514d\u4e86\u5e7b\u8bfb\u95ee\u9898\u3002<\/p>\n<p><\/div><\/div>\n<h1>\u5bf9\u8c61\u5728jvm\u4e2d\u662f\u600e\u4e48\u5b58\u50a8\u7684<\/h1>\n<p>\u5728 Java \u865a\u62df\u673a\uff08JVM\uff09\u4e2d\uff0c\u5bf9\u8c61\u7684\u5b58\u50a8\u6d89\u53ca\u591a\u4e2a\u5185\u5b58\u533a\u57df\uff0c\u5305\u62ec\u5806\uff08Heap\uff09\u3001\u6808\uff08Stack\uff09\u3001\u65b9\u6cd5\u533a\uff08Method Area\uff09\u7b49\u3002\u4ee5\u4e0b\u662f\u5bf9\u8c61\u5728 JVM \u4e2d\u7684\u5b58\u50a8\u65b9\u5f0f\u7684\u8be6\u7ec6\u89e3\u91ca\uff1a<\/p>\n<h2>1. <strong>\u5806\uff08Heap\uff09<\/strong><\/h2>\n<p>\u5806\u662f JVM \u4e2d\u7528\u4e8e\u5b58\u50a8\u5bf9\u8c61\u7684\u4e3b\u8981\u5185\u5b58\u533a\u57df\u3002\u6240\u6709\u901a\u8fc7 <code>new<\/code> \u5173\u952e\u5b57\u521b\u5efa\u7684\u5bf9\u8c61\u5b9e\u4f8b\u90fd\u5b58\u50a8\u5728\u5806\u4e2d\u3002\u5806\u662f\u7ebf\u7a0b\u5171\u4eab\u7684\u5185\u5b58\u533a\u57df\uff0c\u7528\u4e8e\u5b58\u50a8\u52a8\u6001\u5206\u914d\u7684\u5bf9\u8c61\u3002<\/p>\n<h3>1.1 <strong>\u5bf9\u8c61\u5b9e\u4f8b<\/strong><\/h3>\n<ul>\n<li><strong>\u5bf9\u8c61\u5b9e\u4f8b<\/strong>\uff1a\u5bf9\u8c61\u7684\u5b9e\u4f8b\u6570\u636e\uff08\u5b57\u6bb5\uff09\u5b58\u50a8\u5728\u5806\u4e2d\u3002\u6bcf\u4e2a\u5bf9\u8c61\u5b9e\u4f8b\u5305\u542b\u4ee5\u4e0b\u5185\u5bb9\uff1a\n<ul>\n<li><strong>\u5bf9\u8c61\u5934\uff08Object Header\uff09<\/strong>\uff1a\u5305\u542b\u5bf9\u8c61\u7684\u5143\u6570\u636e\uff0c\u5982\u5bf9\u8c61\u7684\u54c8\u5e0c\u7801\u3001\u9501\u4fe1\u606f\u3001GC \u4fe1\u606f\u7b49\u3002<\/li>\n<li><strong>\u5b9e\u4f8b\u6570\u636e\uff08Instance Data\uff09<\/strong>\uff1a\u5bf9\u8c61\u7684\u5b57\u6bb5\u6570\u636e\uff0c\u5305\u62ec\u57fa\u672c\u7c7b\u578b\u548c\u5f15\u7528\u7c7b\u578b\u3002<\/li>\n<li><strong>\u5bf9\u9f50\u586b\u5145\uff08Padding\uff09<\/strong>\uff1a\u4e3a\u4e86\u5bf9\u9f50\u5185\u5b58\uff0cJVM \u53ef\u80fd\u4f1a\u5728\u5bf9\u8c61\u672b\u5c3e\u6dfb\u52a0\u586b\u5145\u5b57\u8282\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h3>1.2 <strong>\u5bf9\u8c61\u5f15\u7528<\/strong><\/h3>\n<ul>\n<li><strong>\u5bf9\u8c61\u5f15\u7528<\/strong>\uff1a\u5bf9\u8c61\u7684\u5f15\u7528\u5b58\u50a8\u5728\u6808\u6216\u5806\u4e2d\uff0c\u6307\u5411\u5806\u4e2d\u7684\u5bf9\u8c61\u5b9e\u4f8b\u3002\u5f15\u7528\u672c\u8eab\u662f\u4e00\u4e2a\u6307\u9488\u6216\u53e5\u67c4\uff0c\u6307\u5411\u5bf9\u8c61\u5728\u5806\u4e2d\u7684\u5730\u5740\u3002<\/li>\n<\/ul>\n<h2>2. <strong>\u6808\uff08Stack\uff09<\/strong><\/h2>\n<p>\u6808\u662f\u7ebf\u7a0b\u79c1\u6709\u7684\u5185\u5b58\u533a\u57df\uff0c\u7528\u4e8e\u5b58\u50a8\u5c40\u90e8\u53d8\u91cf\u3001\u65b9\u6cd5\u53c2\u6570\u3001\u8fd4\u56de\u503c\u548c\u63a7\u5236\u6d41\u4fe1\u606f\u3002\u6808\u4e2d\u7684\u6bcf\u4e2a\u65b9\u6cd5\u8c03\u7528\u90fd\u4f1a\u521b\u5efa\u4e00\u4e2a\u6808\u5e27\uff08Stack Frame\uff09\uff0c\u6808\u5e27\u4e2d\u5b58\u50a8\u4e86\u65b9\u6cd5\u7684\u5c40\u90e8\u53d8\u91cf\u548c\u64cd\u4f5c\u6570\u6808\u3002<\/p>\n<h3>2.1 <strong>\u5c40\u90e8\u53d8\u91cf<\/strong><\/h3>\n<ul>\n<li><strong>\u5c40\u90e8\u53d8\u91cf<\/strong>\uff1a\u65b9\u6cd5\u4e2d\u7684\u5c40\u90e8\u53d8\u91cf\u5b58\u50a8\u5728\u6808\u5e27\u7684\u5c40\u90e8\u53d8\u91cf\u8868\u4e2d\u3002\u5c40\u90e8\u53d8\u91cf\u53ef\u4ee5\u662f\u57fa\u672c\u7c7b\u578b\u6216\u5bf9\u8c61\u5f15\u7528\u3002\n<ul>\n<li><strong>\u57fa\u672c\u7c7b\u578b<\/strong>\uff1a\u5982 <code>int<\/code>, <code>boolean<\/code>, <code>char<\/code> \u7b49\uff0c\u76f4\u63a5\u5b58\u50a8\u5728\u6808\u5e27\u4e2d\u3002<\/li>\n<li><strong>\u5bf9\u8c61\u5f15\u7528<\/strong>\uff1a\u5b58\u50a8\u5728\u6808\u5e27\u4e2d\uff0c\u6307\u5411\u5806\u4e2d\u7684\u5bf9\u8c61\u5b9e\u4f8b\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h2>3. <strong>\u65b9\u6cd5\u533a\uff08Method Area\uff09<\/strong><\/h2>\n<p>\u65b9\u6cd5\u533a\u662f JVM \u4e2d\u7528\u4e8e\u5b58\u50a8\u7c7b\u4fe1\u606f\u3001\u5e38\u91cf\u3001\u9759\u6001\u53d8\u91cf\u3001\u5373\u65f6\u7f16\u8bd1\u5668\u7f16\u8bd1\u540e\u7684\u4ee3\u7801\u7b49\u6570\u636e\u7684\u5185\u5b58\u533a\u57df\u3002\u65b9\u6cd5\u533a\u662f\u7ebf\u7a0b\u5171\u4eab\u7684\u5185\u5b58\u533a\u57df\u3002<\/p>\n<h3>3.1 <strong>\u7c7b\u4fe1\u606f<\/strong><\/h3>\n<ul>\n<li><strong>\u7c7b\u4fe1\u606f<\/strong>\uff1a\u7c7b\u7684\u5143\u6570\u636e\uff08\u5982\u7c7b\u540d\u3001\u7236\u7c7b\u3001\u63a5\u53e3\u3001\u5b57\u6bb5\u3001\u65b9\u6cd5\u7b49\uff09\u5b58\u50a8\u5728\u65b9\u6cd5\u533a\u4e2d\u3002<\/li>\n<\/ul>\n<h3>3.2 <strong>\u9759\u6001\u53d8\u91cf<\/strong><\/h3>\n<ul>\n<li><strong>\u9759\u6001\u53d8\u91cf<\/strong>\uff1a\u7c7b\u7684\u9759\u6001\u53d8\u91cf\uff08<code>static<\/code> \u4fee\u9970\u7684\u53d8\u91cf\uff09\u5b58\u50a8\u5728\u65b9\u6cd5\u533a\u4e2d\u3002\u9759\u6001\u53d8\u91cf\u5728\u7c7b\u52a0\u8f7d\u65f6\u521d\u59cb\u5316\uff0c\u5e76\u5728\u6574\u4e2a JVM \u751f\u547d\u5468\u671f\u5185\u6709\u6548\u3002<\/li>\n<\/ul>\n<h3>3.3 <strong>\u5e38\u91cf\u6c60<\/strong><\/h3>\n<ul>\n<li><strong>\u5e38\u91cf\u6c60<\/strong>\uff1a\u7c7b\u7684\u5e38\u91cf\u6c60\uff08Constant Pool\uff09\u5b58\u50a8\u5728\u65b9\u6cd5\u533a\u4e2d\uff0c\u5305\u542b\u7c7b\u4e2d\u4f7f\u7528\u7684\u5e38\u91cf\uff08\u5982\u5b57\u7b26\u4e32\u5e38\u91cf\u3001\u6570\u5b57\u5e38\u91cf\u7b49\uff09\u3002<\/li>\n<\/ul>\n<h2>4. <strong>\u793a\u4f8b\u4ee3\u7801<\/strong><\/h2>\n<p>\u4ee5\u4e0b\u662f\u4e00\u4e2a\u7b80\u5355\u7684 Java \u7c7b\uff0c\u5c55\u793a\u4e86\u5bf9\u8c61\u5728 JVM \u4e2d\u7684\u5b58\u50a8\u65b9\u5f0f\uff1a<\/p>\n<pre><code class=\"language-java\">public class MyClass {\n    \/\/ \u9759\u6001\u53d8\u91cf\uff0c\u5b58\u50a8\u5728\u65b9\u6cd5\u533a\n    private static int staticVar = 10;\n\n    \/\/ \u5b9e\u4f8b\u53d8\u91cf\uff0c\u5b58\u50a8\u5728\u5806\u4e2d\u7684\u5bf9\u8c61\u5b9e\u4f8b\n    private int instanceVar;\n\n    \/\/ \u6784\u9020\u5668\n    public MyClass(int value) {\n        \/\/ \u5c40\u90e8\u53d8\u91cf\uff0c\u5b58\u50a8\u5728\u6808\u5e27\u4e2d\n        int localVar = value;\n        this.instanceVar = localVar;\n    }\n\n    public static void main(String[] args) {\n        \/\/ \u5bf9\u8c61\u5f15\u7528\uff0c\u5b58\u50a8\u5728\u6808\u5e27\u4e2d\n        MyClass obj = new MyClass(20);\n    }\n}<\/code><\/pre>\n<h2>5. <strong>\u603b\u7ed3<\/strong><\/h2>\n<p>\u5728 JVM \u4e2d\uff0c\u5bf9\u8c61\u7684\u5b58\u50a8\u6d89\u53ca\u591a\u4e2a\u5185\u5b58\u533a\u57df\uff1a<\/p>\n<ul>\n<li><strong>\u5806<\/strong>\uff1a\u5b58\u50a8\u5bf9\u8c61\u5b9e\u4f8b\u548c\u5bf9\u8c61\u5f15\u7528\u3002<\/li>\n<li><strong>\u6808<\/strong>\uff1a\u5b58\u50a8\u5c40\u90e8\u53d8\u91cf\u3001\u65b9\u6cd5\u53c2\u6570\u548c\u8fd4\u56de\u503c\u3002<\/li>\n<li><strong>\u65b9\u6cd5\u533a<\/strong>\uff1a\u5b58\u50a8\u7c7b\u4fe1\u606f\u3001\u9759\u6001\u53d8\u91cf\u548c\u5e38\u91cf\u6c60\u3002<\/li>\n<\/ul>\n<p>\u901a\u8fc7\u8fd9\u4e9b\u5185\u5b58\u533a\u57df\uff0cJVM \u5b9e\u73b0\u4e86\u5bf9\u8c61\u7684\u521b\u5efa\u3001\u5b58\u50a8\u548c\u8bbf\u95ee\u3002\u7406\u89e3\u5bf9\u8c61\u5728 JVM \u4e2d\u7684\u5b58\u50a8\u65b9\u5f0f\u6709\u52a9\u4e8e\u5f00\u53d1\u8005\u66f4\u597d\u5730\u638c\u63e1 Java \u7684\u5185\u5b58\u7ba1\u7406\u548c\u5bf9\u8c61\u751f\u547d\u5468\u671f\u3002<\/p>\n<h1>\u6570\u636e\u5728es\u4e2d\u662f\u5982\u4f55\u5b58\u50a8\u7684<\/h1>\n<h2>1. \u6587\u6863\uff08Document\uff09<\/h2>\n<ul>\n<li><strong>\u6587\u6863<\/strong>\u662f Elasticsearch \u4e2d\u7684\u57fa\u672c\u6570\u636e\u5355\u5143\u3002\u6bcf\u4e2a\u6587\u6863\u90fd\u6709\u4e00\u4e2a\u552f\u4e00\u7684 ID\uff0c\u5e76\u4e14\u5c5e\u4e8e\u4e00\u4e2a\u7279\u5b9a\u7684\u7c7b\u578b\uff08\u5728 Elasticsearch 7.x \u53ca\u66f4\u9ad8\u7248\u672c\u4e2d\uff0c\u7c7b\u578b\u5df2\u88ab\u5f03\u7528\uff0c\u901a\u5e38\u4f7f\u7528\u9ed8\u8ba4\u7c7b\u578b <code>_doc<\/code>\uff09\u3002<\/li>\n<li>\u6587\u6863\u4ee5 JSON \u683c\u5f0f\u8868\u793a\uff0c\u5305\u542b\u5b57\u6bb5\uff08Field\uff09\u548c\u5bf9\u5e94\u7684\u503c\u3002<\/li>\n<\/ul>\n<h2>2. \u7d22\u5f15\uff08Index\uff09<\/h2>\n<ul>\n<li><strong>\u7d22\u5f15<\/strong>\u662f\u6587\u6863\u7684\u96c6\u5408\u3002\u6bcf\u4e2a\u7d22\u5f15\u90fd\u6709\u4e00\u4e2a\u540d\u79f0\uff0c\u7528\u4e8e\u6807\u8bc6\u548c\u8bbf\u95ee\u5176\u4e2d\u7684\u6587\u6863\u3002<\/li>\n<li>\u7d22\u5f15\u5728\u903b\u8f91\u4e0a\u7c7b\u4f3c\u4e8e\u5173\u7cfb\u578b\u6570\u636e\u5e93\u4e2d\u7684\u8868\uff0c\u4f46\u5b83\u4eec\u5728\u7269\u7406\u5b58\u50a8\u548c\u6570\u636e\u7ec4\u7ec7\u65b9\u5f0f\u4e0a\u6709\u6240\u4e0d\u540c\u3002<\/li>\n<\/ul>\n<h2>3. \u5206\u7247\uff08Shard\uff09<\/h2>\n<ul>\n<li>\u4e3a\u4e86\u5b9e\u73b0\u6c34\u5e73\u6269\u5c55\u548c\u9ad8\u53ef\u7528\u6027\uff0cElasticsearch \u5c06\u7d22\u5f15\u5206\u6210\u591a\u4e2a\u5206\u7247\uff08Shard\uff09\u3002\u6bcf\u4e2a\u5206\u7247\u662f\u4e00\u4e2a\u72ec\u7acb\u7684 Lucene \u7d22\u5f15\u3002<\/li>\n<li>\u5206\u7247\u53ef\u4ee5\u662f\u4e3b\u5206\u7247\uff08Primary Shard\uff09\u6216\u526f\u672c\u5206\u7247\uff08Replica Shard\uff09\u3002\u4e3b\u5206\u7247\u7528\u4e8e\u5904\u7406\u5199\u64cd\u4f5c\uff0c\u526f\u672c\u5206\u7247\u7528\u4e8e\u63d0\u4f9b\u8bfb\u64cd\u4f5c\u548c\u6570\u636e\u5197\u4f59\u3002<\/li>\n<\/ul>\n<h2>4. \u5012\u6392\u7d22\u5f15\uff08Inverted Index\uff09<\/h2>\n<ul>\n<li>Elasticsearch \u4f7f\u7528\u5012\u6392\u7d22\u5f15\uff08Inverted Index\uff09\u6765\u5b9e\u73b0\u5feb\u901f\u7684\u5168\u6587\u641c\u7d22\u3002\u5012\u6392\u7d22\u5f15\u5c06\u6587\u6863\u4e2d\u7684\u6bcf\u4e2a\u8bcd\u6620\u5c04\u5230\u5305\u542b\u8be5\u8bcd\u7684\u6587\u6863\u5217\u8868\u3002<\/li>\n<li>\u5012\u6392\u7d22\u5f15\u662f Lucene \u7684\u6838\u5fc3\u6570\u636e\u7ed3\u6784\uff0c\u5b83\u5141\u8bb8 Elasticsearch \u5728\u6beb\u79d2\u7ea7\u65f6\u95f4\u5185\u5b8c\u6210\u590d\u6742\u7684\u641c\u7d22\u67e5\u8be2\u3002<\/li>\n<\/ul>\n<h2>5. \u6bb5\uff08Segment\uff09<\/h2>\n<ul>\n<li>\u5728 Lucene \u4e2d\uff0c\u5206\u7247\u7531\u591a\u4e2a\u6bb5\uff08Segment\uff09\u7ec4\u6210\u3002\u6bcf\u4e2a\u6bb5\u662f\u4e00\u4e2a\u5c0f\u7684\u3001\u4e0d\u53ef\u53d8\u7684 Lucene \u7d22\u5f15\u3002<\/li>\n<li>\u5f53\u6587\u6863\u88ab\u6dfb\u52a0\u6216\u5220\u9664\u65f6\uff0cLucene \u4f1a\u521b\u5efa\u65b0\u7684\u6bb5\u6216\u5408\u5e76\u73b0\u6709\u7684\u6bb5\u3002\u6bb5\u7684\u7ba1\u7406\u548c\u5408\u5e76\u7531 Elasticsearch \u81ea\u52a8\u5904\u7406\u3002<\/li>\n<\/ul>\n<h2>6. \u5b58\u50a8\uff08Storage\uff09<\/h2>\n<ul>\n<li>Elasticsearch \u652f\u6301\u591a\u79cd\u5b58\u50a8\u540e\u7aef\uff0c\u5305\u62ec\u672c\u5730\u78c1\u76d8\u3001\u7f51\u7edc\u6587\u4ef6\u7cfb\u7edf\uff08NFS\uff09\u3001\u4e91\u5b58\u50a8\u7b49\u3002<\/li>\n<li>\u6570\u636e\u4ee5\u4e8c\u8fdb\u5236\u683c\u5f0f\u5b58\u50a8\u5728\u78c1\u76d8\u4e0a\uff0c\u5e76\u4e14\u53ef\u4ee5\u901a\u8fc7\u914d\u7f6e\u6765\u4f18\u5316\u5b58\u50a8\u6027\u80fd\u548c\u6210\u672c\u3002<\/li>\n<\/ul>\n<h2>7. \u96c6\u7fa4\uff08Cluster\uff09<\/h2>\n<ul>\n<li>Elasticsearch \u662f\u4e00\u4e2a\u5206\u5e03\u5f0f\u7cfb\u7edf\uff0c\u6570\u636e\u53ef\u4ee5\u5206\u5e03\u5728\u591a\u4e2a\u8282\u70b9\uff08Node\uff09\u4e0a\u3002\u96c6\u7fa4\uff08Cluster\uff09\u7531\u591a\u4e2a\u8282\u70b9\u7ec4\u6210\uff0c\u5171\u540c\u5b58\u50a8\u548c\u5904\u7406\u6570\u636e\u3002<\/li>\n<li>\u96c6\u7fa4\u4e2d\u7684\u6bcf\u4e2a\u8282\u70b9\u53ef\u4ee5\u5b58\u50a8\u90e8\u5206\u6570\u636e\uff0c\u5e76\u4e14\u901a\u8fc7\u5185\u90e8\u901a\u4fe1\u534f\u8bae\uff08\u5982 Zen Discovery\uff09\u6765\u534f\u8c03\u6570\u636e\u5206\u5e03\u548c\u590d\u5236\u3002<\/li>\n<\/ul>\n<h2>8. \u6570\u636e\u5199\u5165\u6d41\u7a0b<\/h2>\n<ul>\n<li>\u5f53\u6587\u6863\u88ab\u5199\u5165 Elasticsearch \u65f6\uff0c\u5b83\u9996\u5148\u88ab\u8def\u7531\u5230\u4e00\u4e2a\u4e3b\u5206\u7247\u3002\u4e3b\u5206\u7247\u5904\u7406\u5199\u64cd\u4f5c\uff0c\u5e76\u5c06\u6570\u636e\u590d\u5236\u5230\u76f8\u5173\u7684\u526f\u672c\u5206\u7247\u3002<\/li>\n<li>\u5199\u64cd\u4f5c\u5b8c\u6210\u540e\uff0c\u6587\u6863\u4f1a\u88ab\u7d22\u5f15\u5e76\u5b58\u50a8\u5728 Lucene \u6bb5\u4e2d\u3002<\/li>\n<\/ul>\n<h2>9. \u6570\u636e\u8bfb\u53d6\u6d41\u7a0b<\/h2>\n<ul>\n<li>\u5f53\u6267\u884c\u641c\u7d22\u67e5\u8be2\u65f6\uff0c\u67e5\u8be2\u4f1a\u88ab\u53d1\u9001\u5230\u96c6\u7fa4\u4e2d\u7684\u4e00\u4e2a\u6216\u591a\u4e2a\u8282\u70b9\u3002\u8282\u70b9\u4f1a\u6839\u636e\u67e5\u8be2\u6761\u4ef6\u4ece\u76f8\u5173\u7684\u5206\u7247\u4e2d\u8bfb\u53d6\u6570\u636e\u3002<\/li>\n<li>\u6570\u636e\u901a\u8fc7\u5012\u6392\u7d22\u5f15\u8fdb\u884c\u5feb\u901f\u68c0\u7d22\uff0c\u5e76\u5c06\u7ed3\u679c\u8fd4\u56de\u7ed9\u5ba2\u6237\u7aef\u3002<\/li>\n<\/ul>\n<h1>\u56de\u8868\u7684\u89e3\u51b3\u65b9\u6848<\/h1>\n<p>\u5728 MySQL \u4e2d\uff0c\u56de\u8868\uff08Lookup\uff09\u662f\u6307\u5728\u6267\u884c\u67e5\u8be2\u65f6\uff0cInnoDB \u5b58\u50a8\u5f15\u64ce\u9700\u8981\u4ece\u4e8c\u7ea7\u7d22\u5f15\uff08Secondary Index\uff09\u4e2d\u83b7\u53d6\u4e3b\u952e\uff08Primary Key\uff09\uff0c\u7136\u540e\u518d\u6839\u636e\u4e3b\u952e\u5230\u805a\u7c07\u7d22\u5f15\uff08Clustered Index\uff09\u4e2d\u67e5\u627e\u5b8c\u6574\u7684\u884c\u6570\u636e\u3002\u8fd9\u79cd\u989d\u5916\u7684\u67e5\u627e\u64cd\u4f5c\u4f1a\u589e\u52a0\u67e5\u8be2\u7684\u5f00\u9500\uff0c\u5c24\u5176\u662f\u5728\u4e8c\u7ea7\u7d22\u5f15\u8986\u76d6\u4e0d\u5168\u7684\u60c5\u51b5\u4e0b\u3002<\/p>\n<h2>\u56de\u8868\u7684\u539f\u56e0<\/h2>\n<ul>\n<li><strong>\u4e8c\u7ea7\u7d22\u5f15\u4e0d\u5b8c\u6574<\/strong>\uff1a\u4e8c\u7ea7\u7d22\u5f15\u53ea\u5305\u542b\u7d22\u5f15\u5217\u548c\u4e3b\u952e\u5217\uff0c\u4e0d\u5305\u542b\u8868\u4e2d\u7684\u6240\u6709\u5217\u3002\u56e0\u6b64\uff0c\u5f53\u67e5\u8be2\u9700\u8981\u83b7\u53d6\u4e0d\u5728\u4e8c\u7ea7\u7d22\u5f15\u4e2d\u7684\u5217\u65f6\uff0c\u5c31\u9700\u8981\u56de\u8868\u5230\u805a\u7c07\u7d22\u5f15\u4e2d\u67e5\u627e\u5b8c\u6574\u7684\u884c\u6570\u636e\u3002<\/li>\n<li><strong>\u67e5\u8be2\u6761\u4ef6\u4e0d\u5339\u914d<\/strong>\uff1a\u5982\u679c\u67e5\u8be2\u6761\u4ef6\u4e0d\u5339\u914d\u4e8c\u7ea7\u7d22\u5f15\u4e2d\u7684\u5217\uff0cMySQL \u53ef\u80fd\u9700\u8981\u56de\u8868\u4ee5\u83b7\u53d6\u66f4\u591a\u7684\u6570\u636e\u6765\u6ee1\u8db3\u67e5\u8be2\u6761\u4ef6\u3002<\/li>\n<\/ul>\n<h2>\u56de\u8868\u7684\u89e3\u51b3\u65b9\u6848<\/h2>\n<h3>1. <strong>\u8986\u76d6\u7d22\u5f15\uff08Covering Index\uff09<\/strong><\/h3>\n<ul>\n<li>\n<p><strong>\u5b9a\u4e49<\/strong>: \u8986\u76d6\u7d22\u5f15\u662f\u6307\u4e00\u4e2a\u7d22\u5f15\u5305\u542b\u4e86\u67e5\u8be2\u6240\u9700\u7684\u6240\u6709\u5217\u3002\u8fd9\u6837\uff0cMySQL \u53ef\u4ee5\u76f4\u63a5\u4ece\u7d22\u5f15\u4e2d\u83b7\u53d6\u6240\u6709\u9700\u8981\u7684\u6570\u636e\uff0c\u800c\u4e0d\u9700\u8981\u56de\u8868\u5230\u805a\u7c07\u7d22\u5f15\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u5b9e\u73b0<\/strong>: \u5728\u521b\u5efa\u7d22\u5f15\u65f6\uff0c\u5c06\u67e5\u8be2\u4e2d\u9700\u8981\u7684\u6240\u6709\u5217\u90fd\u5305\u542b\u5728\u7d22\u5f15\u4e2d\u3002\u4f8b\u5982\uff0c\u5982\u679c\u67e5\u8be2\u9700\u8981 <code>name<\/code> \u548c <code>age<\/code> \u5217\uff0c\u53ef\u4ee5\u521b\u5efa\u4e00\u4e2a\u590d\u5408\u7d22\u5f15 <code>(name, age)<\/code>\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u793a\u4f8b<\/strong>:<\/p>\n<pre><code class=\"language-sql\"> CREATE INDEX idx_name_age ON users(name, age);<\/code><\/pre>\n<p>\u8fd9\u6837\uff0c\u67e5\u8be2 <code>SELECT name, age FROM users WHERE name = &#039;John&#039;;<\/code> \u5c31\u53ef\u4ee5\u76f4\u63a5\u4ece\u7d22\u5f15\u4e2d\u83b7\u53d6\u6570\u636e\uff0c\u800c\u4e0d\u9700\u8981\u56de\u8868\u3002<\/p>\n<\/li>\n<\/ul>\n<h3>2. <strong>\u7d22\u5f15\u5408\u5e76\uff08Index Merge\uff09<\/strong><\/h3>\n<ul>\n<li><strong>\u5b9a\u4e49<\/strong>: \u7d22\u5f15\u5408\u5e76\u662f\u6307 MySQL \u4f7f\u7528\u591a\u4e2a\u7d22\u5f15\u7684\u4ea4\u96c6\u6216\u5e76\u96c6\u6765\u6ee1\u8db3\u67e5\u8be2\u6761\u4ef6\uff0c\u800c\u4e0d\u9700\u8981\u56de\u8868\u3002<\/li>\n<li><strong>\u5b9e\u73b0<\/strong>: MySQL \u4f1a\u81ea\u52a8\u9009\u62e9\u5408\u9002\u7684\u7d22\u5f15\u5408\u5e76\u7b56\u7565\uff0c\u901a\u5e38\u4e0d\u9700\u8981\u624b\u52a8\u5e72\u9884\u3002<\/li>\n<li><strong>\u793a\u4f8b<\/strong>: \u5982\u679c\u8868\u4e2d\u6709\u4e24\u4e2a\u7d22\u5f15 <code>idx_name<\/code> \u548c <code>idx_age<\/code>\uff0c\u67e5\u8be2 <code>SELECT * FROM users WHERE name = &#039;John&#039; AND age = 30;<\/code> \u53ef\u80fd\u4f1a\u4f7f\u7528\u7d22\u5f15\u5408\u5e76\u6765\u907f\u514d\u56de\u8868\u3002<\/li>\n<\/ul>\n<h3>3. <strong>\u5ef6\u8fdf\u5173\u8054\uff08Delayed Join\uff09<\/strong><\/h3>\n<ul>\n<li>\n<p><strong>\u5b9a\u4e49<\/strong>: \u5ef6\u8fdf\u5173\u8054\u662f\u6307\u5728\u67e5\u8be2\u4e2d\u5148\u901a\u8fc7\u4e8c\u7ea7\u7d22\u5f15\u83b7\u53d6\u4e3b\u952e\uff0c\u7136\u540e\u518d\u901a\u8fc7\u4e3b\u952e\u8fdb\u884c\u5173\u8054\u67e5\u8be2\uff0c\u4ece\u800c\u51cf\u5c11\u56de\u8868\u7684\u6b21\u6570\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u5b9e\u73b0<\/strong>: \u5728\u67e5\u8be2\u4e2d\u5148\u901a\u8fc7\u4e8c\u7ea7\u7d22\u5f15\u83b7\u53d6\u4e3b\u952e\uff0c\u7136\u540e\u518d\u901a\u8fc7\u4e3b\u952e\u8fdb\u884c\u5173\u8054\u67e5\u8be2\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u793a\u4f8b<\/strong>:<\/p>\n<pre><code class=\"language-sql\"> SELECT u.*\n FROM (SELECT id FROM users WHERE name = 'John') AS t\n JOIN users u ON t.id = u.id;<\/code><\/pre>\n<p>\u8fd9\u6837\uff0cMySQL \u53ea\u9700\u8981\u56de\u8868\u4e00\u6b21\uff0c\u800c\u4e0d\u662f\u6bcf\u6b21\u90fd\u56de\u8868\u3002<\/p>\n<\/li>\n<\/ul>\n<h3>4. <strong>\u4f7f\u7528\u4e3b\u952e\u67e5\u8be2<\/strong><\/h3>\n<ul>\n<li>\n<p><strong>\u5b9a\u4e49<\/strong>: \u5982\u679c\u67e5\u8be2\u6761\u4ef6\u53ef\u4ee5\u76f4\u63a5\u4f7f\u7528\u4e3b\u952e\uff0cMySQL \u53ef\u4ee5\u76f4\u63a5\u4ece\u805a\u7c07\u7d22\u5f15\u4e2d\u83b7\u53d6\u6570\u636e\uff0c\u800c\u4e0d\u9700\u8981\u56de\u8868\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u5b9e\u73b0<\/strong>: \u5c3d\u91cf\u4f7f\u7528\u4e3b\u952e\u4f5c\u4e3a\u67e5\u8be2\u6761\u4ef6\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u793a\u4f8b<\/strong>:<\/p>\n<pre><code class=\"language-sql\"> SELECT * FROM users WHERE id = 123;<\/code><\/pre>\n<p>\u8fd9\u6837\uff0cMySQL \u53ef\u4ee5\u76f4\u63a5\u4ece\u805a\u7c07\u7d22\u5f15\u4e2d\u83b7\u53d6\u6570\u636e\uff0c\u800c\u4e0d\u9700\u8981\u56de\u8868\u3002<\/p>\n<\/li>\n<\/ul>\n<h3>5. <strong>\u4f18\u5316\u67e5\u8be2\u6761\u4ef6<\/strong><\/h3>\n<ul>\n<li><strong>\u5b9a\u4e49<\/strong>: \u4f18\u5316\u67e5\u8be2\u6761\u4ef6\uff0c\u4f7f\u5176\u5c3d\u53ef\u80fd\u5339\u914d\u4e8c\u7ea7\u7d22\u5f15\u4e2d\u7684\u5217\uff0c\u4ece\u800c\u51cf\u5c11\u56de\u8868\u7684\u6b21\u6570\u3002<\/li>\n<li><strong>\u5b9e\u73b0<\/strong>: \u786e\u4fdd\u67e5\u8be2\u6761\u4ef6\u5c3d\u53ef\u80fd\u5339\u914d\u4e8c\u7ea7\u7d22\u5f15\u4e2d\u7684\u5217\u3002<\/li>\n<li><strong>\u793a\u4f8b<\/strong>: \u5982\u679c\u8868\u4e2d\u6709\u7d22\u5f15 <code>idx_name_age<\/code>\uff0c\u67e5\u8be2 <code>SELECT * FROM users WHERE name = &#039;John&#039; AND age = 30;<\/code> \u4f1a\u6bd4 <code>SELECT * FROM users WHERE name = &#039;John&#039;;<\/code> \u66f4\u9ad8\u6548\uff0c\u56e0\u4e3a\u540e\u8005\u53ef\u80fd\u9700\u8981\u56de\u8868\u3002<\/li>\n<\/ul>\n<h3>6. <strong>\u4f7f\u7528\u7d22\u5f15\u63d0\u793a\uff08Index Hint\uff09<\/strong><\/h3>\n<ul>\n<li>\n<p><strong>\u5b9a\u4e49<\/strong>: \u7d22\u5f15\u63d0\u793a\u53ef\u4ee5\u5f3a\u5236 MySQL \u4f7f\u7528\u6307\u5b9a\u7684\u7d22\u5f15\uff0c\u4ece\u800c\u907f\u514d\u56de\u8868\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u5b9e\u73b0<\/strong>: \u5728\u67e5\u8be2\u4e2d\u4f7f\u7528 <code>USE INDEX<\/code>\u3001<code>FORCE INDEX<\/code> \u6216 <code>IGNORE INDEX<\/code> \u63d0\u793a\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u793a\u4f8b<\/strong>:<\/p>\n<pre><code class=\"language-sql\"> SELECT * FROM users USE INDEX (idx_name) WHERE name = 'John';<\/code><\/pre>\n<p>\u8fd9\u6837\uff0cMySQL \u4f1a\u5f3a\u5236\u4f7f\u7528 <code>idx_name<\/code> \u7d22\u5f15\uff0c\u4ece\u800c\u907f\u514d\u56de\u8868\u3002<\/p>\n<\/li>\n<\/ul>\n<h3>7. <strong>\u51cf\u5c11\u67e5\u8be2\u5217<\/strong><\/h3>\n<ul>\n<li>\n<p><strong>\u5b9a\u4e49<\/strong>: \u51cf\u5c11\u67e5\u8be2\u4e2d\u8fd4\u56de\u7684\u5217\uff0c\u4f7f\u5176\u5c3d\u53ef\u80fd\u5339\u914d\u4e8c\u7ea7\u7d22\u5f15\u4e2d\u7684\u5217\uff0c\u4ece\u800c\u51cf\u5c11\u56de\u8868\u7684\u6b21\u6570\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u5b9e\u73b0<\/strong>: \u53ea\u67e5\u8be2\u9700\u8981\u7684\u5217\uff0c\u800c\u4e0d\u662f\u4f7f\u7528 <code>SELECT *<\/code>\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u793a\u4f8b<\/strong>:<\/p>\n<pre><code class=\"language-sql\"> SELECT name, age FROM users WHERE name = 'John';<\/code><\/pre>\n<p>\u8fd9\u6837\uff0cMySQL \u53ef\u4ee5\u76f4\u63a5\u4ece\u7d22\u5f15\u4e2d\u83b7\u53d6 <code>name<\/code> \u548c <code>age<\/code> \u5217\uff0c\u800c\u4e0d\u9700\u8981\u56de\u8868\u3002<\/p>\n<\/li>\n<\/ul>\n<h2>\u603b\u7ed3<\/h2>\n<p>\u56de\u8868\u662f MySQL \u67e5\u8be2\u6027\u80fd\u7684\u4e00\u4e2a\u74f6\u9888\uff0c\u5c24\u5176\u662f\u5728\u4e8c\u7ea7\u7d22\u5f15\u8986\u76d6\u4e0d\u5168\u7684\u60c5\u51b5\u4e0b\u3002\u901a\u8fc7\u4f7f\u7528\u8986\u76d6\u7d22\u5f15\u3001\u7d22\u5f15\u5408\u5e76\u3001\u5ef6\u8fdf\u5173\u8054\u3001\u4f18\u5316\u67e5\u8be2\u6761\u4ef6\u3001\u4f7f\u7528\u7d22\u5f15\u63d0\u793a\u548c\u51cf\u5c11\u67e5\u8be2\u5217\u7b49\u65b9\u6cd5\uff0c\u53ef\u4ee5\u6709\u6548\u51cf\u5c11\u56de\u8868\u7684\u6b21\u6570\uff0c\u4ece\u800c\u63d0\u9ad8\u67e5\u8be2\u6027\u80fd\u3002<\/p>\n<h1>\u8bf4\u4e00\u8bf4redolog\u548cbinlog\u5b9e\u73b0\u4e86\u6570\u636e\u5e93\u7684ACID\u7684\u4e2d\u54ea\u4e2a<\/h1>\n<p>\u5728 MySQL \u4e2d\uff0c<code>redo log<\/code>\uff08\u91cd\u505a\u65e5\u5fd7\uff09\u548c <code>binlog<\/code>\uff08\u4e8c\u8fdb\u5236\u65e5\u5fd7\uff09\u662f\u4e24\u79cd\u4e0d\u540c\u7684\u65e5\u5fd7\u673a\u5236\uff0c\u5b83\u4eec\u5728\u5b9e\u73b0\u6570\u636e\u5e93\u7684 ACID \u7279\u6027\u4e2d\u626e\u6f14\u7740\u4e0d\u540c\u7684\u89d2\u8272\u3002<\/p>\n<h2>1. <strong>redo log\uff08\u91cd\u505a\u65e5\u5fd7\uff09<\/strong><\/h2>\n<h3>\u4f5c\u7528<\/h3>\n<ul>\n<li><strong>\u6301\u4e45\u6027\uff08Durability\uff09<\/strong>\uff1a<code>redo log<\/code> \u4e3b\u8981\u7528\u4e8e\u5b9e\u73b0\u6570\u636e\u5e93\u7684\u6301\u4e45\u6027\uff08D\uff09\u3002\u5b83\u8bb0\u5f55\u4e86\u6240\u6709\u5bf9\u6570\u636e\u9875\u7684\u4fee\u6539\u64cd\u4f5c\uff0c\u4ee5\u4fbf\u5728\u6570\u636e\u5e93\u5d29\u6e83\u540e\u80fd\u591f\u6062\u590d\u8fd9\u4e9b\u4fee\u6539\u3002<\/li>\n<\/ul>\n<h3>\u5de5\u4f5c\u539f\u7406<\/h3>\n<ul>\n<li><strong>WAL\uff08Write-Ahead Logging\uff09<\/strong>\uff1a<code>redo log<\/code> \u91c7\u7528\u9884\u5199\u65e5\u5fd7\uff08WAL\uff09\u673a\u5236\u3002\u5728\u4e8b\u52a1\u63d0\u4ea4\u65f6\uff0cMySQL \u9996\u5148\u5c06\u4e8b\u52a1\u7684\u4fee\u6539\u64cd\u4f5c\u5199\u5165 <code>redo log<\/code>\uff0c\u7136\u540e\u518d\u5c06\u6570\u636e\u5199\u5165\u78c1\u76d8\u3002\u8fd9\u6837\uff0c\u5373\u4f7f\u6570\u636e\u5e93\u5728\u6570\u636e\u5199\u5165\u78c1\u76d8\u4e4b\u524d\u5d29\u6e83\uff0c\u4e5f\u53ef\u4ee5\u901a\u8fc7 <code>redo log<\/code> \u6062\u590d\u672a\u5b8c\u6210\u7684\u4e8b\u52a1\u3002<\/li>\n<li><strong>\u5faa\u73af\u5199\u5165<\/strong>\uff1a<code>redo log<\/code> \u901a\u5e38\u662f\u5faa\u73af\u5199\u5165\u7684\uff0c\u5373\u5f53 <code>redo log<\/code> \u5199\u6ee1\u65f6\uff0c\u4f1a\u8986\u76d6\u6700\u65e9\u7684\u65e5\u5fd7\u8bb0\u5f55\u3002\u56e0\u6b64\uff0c<code>redo log<\/code> \u7684\u5927\u5c0f\u662f\u6709\u9650\u7684\uff0c\u9700\u8981\u5b9a\u671f\u8fdb\u884c\u68c0\u67e5\u70b9\uff08checkpoint\uff09\u64cd\u4f5c\uff0c\u5c06 <code>redo log<\/code> \u4e2d\u7684\u4fee\u6539\u5e94\u7528\u5230\u6570\u636e\u9875\u4e2d\u3002<\/li>\n<\/ul>\n<h3>\u5b9e\u73b0 ACID \u4e2d\u7684\u54ea\u4e2a\u7279\u6027<\/h3>\n<ul>\n<li><strong>\u6301\u4e45\u6027\uff08Durability\uff09<\/strong>\uff1a<code>redo log<\/code> \u786e\u4fdd\u4e86\u6570\u636e\u7684\u6301\u4e45\u6027\uff0c\u5373\u4e00\u65e6\u4e8b\u52a1\u63d0\u4ea4\uff0c\u5373\u4f7f\u6570\u636e\u5e93\u5d29\u6e83\uff0c\u4e8b\u52a1\u7684\u4fee\u6539\u4e5f\u4e0d\u4f1a\u4e22\u5931\u3002<\/li>\n<\/ul>\n<h2>2. <strong>binlog\uff08\u4e8c\u8fdb\u5236\u65e5\u5fd7\uff09<\/strong><\/h2>\n<h3>\u4f5c\u7528<\/h3>\n<ul>\n<li><strong>\u590d\u5236\u548c\u6062\u590d<\/strong>\uff1a<code>binlog<\/code> \u4e3b\u8981\u7528\u4e8e\u6570\u636e\u5e93\u7684\u590d\u5236\u548c\u6062\u590d\u3002\u5b83\u8bb0\u5f55\u4e86\u6240\u6709\u5bf9\u6570\u636e\u5e93\u7684\u4fee\u6539\u64cd\u4f5c\uff08\u5982 <code>INSERT<\/code>\u3001<code>UPDATE<\/code>\u3001<code>DELETE<\/code> \u7b49\uff09\uff0c\u4ee5\u4fbf\u5728\u4e3b\u4ece\u590d\u5236\u6216\u6570\u636e\u5e93\u6062\u590d\u65f6\u4f7f\u7528\u3002<\/li>\n<li><strong>\u4e8b\u52a1\u4e00\u81f4\u6027\uff08Consistency\uff09<\/strong>\uff1a<code>binlog<\/code> \u4e5f\u95f4\u63a5\u5730\u5e2e\u52a9\u5b9e\u73b0\u4e86\u4e8b\u52a1\u7684\u4e00\u81f4\u6027\uff08C\uff09\uff0c\u56e0\u4e3a\u5b83\u8bb0\u5f55\u4e86\u4e8b\u52a1\u7684\u6240\u6709\u64cd\u4f5c\uff0c\u786e\u4fdd\u5728\u4e3b\u4ece\u590d\u5236\u6216\u6062\u590d\u65f6\u80fd\u591f\u4fdd\u6301\u6570\u636e\u7684\u4e00\u81f4\u6027\u3002<\/li>\n<\/ul>\n<h3>\u5de5\u4f5c\u539f\u7406<\/h3>\n<ul>\n<li><strong>\u4e8b\u4ef6\u8bb0\u5f55<\/strong>\uff1a<code>binlog<\/code> \u4ee5\u4e8b\u4ef6\u7684\u5f62\u5f0f\u8bb0\u5f55\u6570\u636e\u5e93\u7684\u4fee\u6539\u64cd\u4f5c\u3002\u6bcf\u4e2a\u4e8b\u4ef6\u5bf9\u5e94\u4e00\u4e2a\u6570\u636e\u5e93\u64cd\u4f5c\uff0c\u5982 <code>INSERT<\/code>\u3001<code>UPDATE<\/code>\u3001<code>DELETE<\/code> \u7b49\u3002<\/li>\n<li><strong>\u987a\u5e8f\u5199\u5165<\/strong>\uff1a<code>binlog<\/code> \u662f\u987a\u5e8f\u5199\u5165\u7684\uff0c\u5373\u6bcf\u4e2a\u4e8b\u52a1\u7684\u4fee\u6539\u64cd\u4f5c\u90fd\u4f1a\u6309\u987a\u5e8f\u8bb0\u5f55\u5728 <code>binlog<\/code> \u4e2d\u3002<code>binlog<\/code> \u901a\u5e38\u662f\u8ffd\u52a0\u5199\u5165\u7684\uff0c\u4e0d\u4f1a\u8986\u76d6\u4e4b\u524d\u7684\u8bb0\u5f55\u3002<\/li>\n<\/ul>\n<h3>\u5b9e\u73b0 ACID \u4e2d\u7684\u54ea\u4e2a\u7279\u6027<\/h3>\n<ul>\n<li><strong>\u4e00\u81f4\u6027\uff08Consistency\uff09<\/strong>\uff1a<code>binlog<\/code> \u901a\u8fc7\u8bb0\u5f55\u4e8b\u52a1\u7684\u6240\u6709\u64cd\u4f5c\uff0c\u786e\u4fdd\u5728\u4e3b\u4ece\u590d\u5236\u6216\u6062\u590d\u65f6\u80fd\u591f\u4fdd\u6301\u6570\u636e\u7684\u4e00\u81f4\u6027\u3002<\/li>\n<li><strong>\u6301\u4e45\u6027\uff08Durability\uff09<\/strong>\uff1a\u867d\u7136 <code>binlog<\/code> \u672c\u8eab\u4e0d\u76f4\u63a5\u5b9e\u73b0\u6301\u4e45\u6027\uff0c\u4f46\u5b83\u8bb0\u5f55\u4e86\u6240\u6709\u7684\u4e8b\u52a1\u64cd\u4f5c\uff0c\u53ef\u4ee5\u5728\u6570\u636e\u5e93\u5d29\u6e83\u540e\u901a\u8fc7 <code>binlog<\/code> \u8fdb\u884c\u6062\u590d\uff0c\u4ece\u800c\u95f4\u63a5\u5730\u5e2e\u52a9\u5b9e\u73b0\u6301\u4e45\u6027\u3002<\/li>\n<\/ul>\n<h2>\u603b\u7ed3<\/h2>\n<ul>\n<li><strong>redo log<\/strong>\uff1a\u4e3b\u8981\u7528\u4e8e\u5b9e\u73b0\u6570\u636e\u5e93\u7684\u6301\u4e45\u6027\uff08Durability\uff09\uff0c\u786e\u4fdd\u4e8b\u52a1\u63d0\u4ea4\u540e\u6570\u636e\u7684\u6301\u4e45\u6027\u3002<\/li>\n<li><strong>binlog<\/strong>\uff1a\u4e3b\u8981\u7528\u4e8e\u6570\u636e\u5e93\u7684\u590d\u5236\u548c\u6062\u590d\uff0c\u95f4\u63a5\u5730\u5e2e\u52a9\u5b9e\u73b0\u4e8b\u52a1\u7684\u4e00\u81f4\u6027\uff08Consistency\uff09\u548c\u6301\u4e45\u6027\uff08Durability\uff09\u3002<\/li>\n<\/ul>\n<p>\u4e24\u8005\u5728 MySQL \u4e2d\u534f\u540c\u5de5\u4f5c\uff0c\u5171\u540c\u786e\u4fdd\u6570\u636e\u5e93\u7684 ACID \u7279\u6027\u3002<\/p>\n<h1>volatile\u5173\u952e\u5b57<\/h1>\n<p><code>volatile<\/code> \u662f Java \u4e2d\u7684\u4e00\u4e2a\u5173\u952e\u5b57\uff0c\u7528\u4e8e\u4fee\u9970\u53d8\u91cf\u3002\u5b83\u4e3b\u8981\u7528\u4e8e\u786e\u4fdd\u591a\u7ebf\u7a0b\u73af\u5883\u4e0b\u53d8\u91cf\u7684\u53ef\u89c1\u6027\u548c\u6709\u5e8f\u6027\u3002<code>volatile<\/code> \u5173\u952e\u5b57\u5728 Java \u5185\u5b58\u6a21\u578b\uff08JMM\uff09\u4e2d\u626e\u6f14\u7740\u91cd\u8981\u7684\u89d2\u8272\uff0c\u7279\u522b\u662f\u5728\u5904\u7406\u5e76\u53d1\u7f16\u7a0b\u65f6\u3002<\/p>\n<h2>1. <strong><code>volatile<\/code> \u7684\u4f5c\u7528<\/strong><\/h2>\n<h3>1.1 <strong>\u53ef\u89c1\u6027\uff08Visibility\uff09<\/strong><\/h3>\n<ul>\n<li><strong>\u5b9a\u4e49<\/strong>: <code>volatile<\/code> \u786e\u4fdd\u4e86\u53d8\u91cf\u7684\u4fee\u6539\u5bf9\u6240\u6709\u7ebf\u7a0b\u662f\u53ef\u89c1\u7684\u3002\u5f53\u4e00\u4e2a\u7ebf\u7a0b\u4fee\u6539\u4e86 <code>volatile<\/code> \u53d8\u91cf\u7684\u503c\u65f6\uff0c\u8fd9\u4e2a\u4fee\u6539\u4f1a\u7acb\u5373\u5237\u65b0\u5230\u4e3b\u5185\u5b58\u4e2d\uff0c\u5e76\u4e14\u5bf9\u5176\u4ed6\u7ebf\u7a0b\u53ef\u89c1\u3002<\/li>\n<li><strong>\u539f\u7406<\/strong>: \u5728 Java \u5185\u5b58\u6a21\u578b\u4e2d\uff0c\u6bcf\u4e2a\u7ebf\u7a0b\u90fd\u6709\u81ea\u5df1\u7684\u5de5\u4f5c\u5185\u5b58\uff08\u7ebf\u7a0b\u79c1\u6709\u7684\u5185\u5b58\u533a\u57df\uff09\uff0c\u7528\u4e8e\u5b58\u50a8\u53d8\u91cf\u7684\u526f\u672c\u3002\u5f53\u4e00\u4e2a\u7ebf\u7a0b\u4fee\u6539\u4e86 <code>volatile<\/code> \u53d8\u91cf\u65f6\uff0c\u8fd9\u4e2a\u4fee\u6539\u4f1a\u7acb\u5373\u5237\u65b0\u5230\u4e3b\u5185\u5b58\u4e2d\uff0c\u5e76\u4e14\u5176\u4ed6\u7ebf\u7a0b\u7684\u5de5\u4f5c\u5185\u5b58\u4e2d\u7684\u526f\u672c\u4f1a\u88ab\u5931\u6548\uff0c\u4ece\u800c\u5f3a\u5236\u5b83\u4eec\u4ece\u4e3b\u5185\u5b58\u4e2d\u91cd\u65b0\u8bfb\u53d6\u6700\u65b0\u7684\u503c\u3002<\/li>\n<\/ul>\n<h3>1.2 <strong>\u6709\u5e8f\u6027\uff08Ordering\uff09<\/strong><\/h3>\n<ul>\n<li><strong>\u5b9a\u4e49<\/strong>: <code>volatile<\/code> \u786e\u4fdd\u4e86\u53d8\u91cf\u7684\u8bfb\u5199\u64cd\u4f5c\u5177\u6709\u4e00\u5b9a\u7684\u6709\u5e8f\u6027\u3002\u5177\u4f53\u6765\u8bf4\uff0c<code>volatile<\/code> \u53d8\u91cf\u7684\u5199\u64cd\u4f5c\u4f1a\u53d1\u751f\u5728\u540e\u7eed\u7684\u8bfb\u64cd\u4f5c\u4e4b\u524d\uff0c\u8fd9\u79f0\u4e3a\u201c\u5199\u524d\u8bfb\u540e\u201d\uff08write-before-read\uff09\u89c4\u5219\u3002<\/li>\n<li><strong>\u539f\u7406<\/strong>: <code>volatile<\/code> \u53d8\u91cf\u7684\u8bfb\u5199\u64cd\u4f5c\u4f1a\u88ab\u63d2\u5165\u5185\u5b58\u5c4f\u969c\uff08Memory Barrier\uff09\uff0c\u4ece\u800c\u9632\u6b62\u6307\u4ee4\u91cd\u6392\u5e8f\u3002\u5185\u5b58\u5c4f\u969c\u786e\u4fdd\u4e86\u5728 <code>volatile<\/code> \u53d8\u91cf\u5199\u64cd\u4f5c\u4e4b\u524d\u7684\u6240\u6709\u64cd\u4f5c\u90fd\u5df2\u5b8c\u6210\uff0c\u5e76\u4e14\u5728 <code>volatile<\/code> \u53d8\u91cf\u8bfb\u64cd\u4f5c\u4e4b\u540e\u7684\u6240\u6709\u64cd\u4f5c\u90fd\u672a\u5f00\u59cb\u3002<\/li>\n<\/ul>\n<h2>2. <strong><code>volatile<\/code> \u7684\u4f7f\u7528\u573a\u666f<\/strong><\/h2>\n<h3>2.1 <strong>\u72b6\u6001\u6807\u5fd7<\/strong><\/h3>\n<ul>\n<li>\n<p><strong>\u573a\u666f<\/strong>: \u5f53\u4e00\u4e2a\u53d8\u91cf\u7528\u4e8e\u6807\u8bb0\u67d0\u4e2a\u72b6\u6001\u65f6\uff0c\u53ef\u4ee5\u4f7f\u7528 <code>volatile<\/code>\u3002\u4f8b\u5982\uff0c\u4e00\u4e2a\u7ebf\u7a0b\u7b49\u5f85\u53e6\u4e00\u4e2a\u7ebf\u7a0b\u5b8c\u6210\u67d0\u4e2a\u4efb\u52a1\uff0c\u53ef\u4ee5\u4f7f\u7528 <code>volatile<\/code> \u53d8\u91cf\u4f5c\u4e3a\u6807\u5fd7\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u793a\u4f8b<\/strong>:<\/p>\n<pre><code class=\"language-java\">public class Task {\n  private volatile boolean done;\n\n  public void setDone() {\n      done = true;\n  }\n\n  public boolean isDone() {\n      return done;\n  }\n}<\/code><\/pre>\n<\/li>\n<\/ul>\n<h3>2.2 <strong>\u5355\u4f8b\u6a21\u5f0f\u4e2d\u7684\u53cc\u91cd\u68c0\u67e5\u9501\u5b9a\uff08Double-Checked Locking\uff09<\/strong><\/h3>\n<ul>\n<li>\n<p><strong>\u573a\u666f<\/strong>: \u5728\u5355\u4f8b\u6a21\u5f0f\u4e2d\uff0c\u4e3a\u4e86\u5ef6\u8fdf\u521d\u59cb\u5316\u5e76\u4e14\u907f\u514d\u591a\u7ebf\u7a0b\u95ee\u9898\uff0c\u53ef\u4ee5\u4f7f\u7528 <code>volatile<\/code> \u4fee\u9970\u5355\u4f8b\u5bf9\u8c61\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u793a\u4f8b<\/strong>:<\/p>\n<pre><code class=\"language-java\">public class Singleton {\n  private static volatile Singleton instance;\n\n  private Singleton() {}\n\n  public static Singleton getInstance() {\n      if (instance == null) {\n          synchronized (Singleton.class) {\n              if (instance == null) {\n                  instance = new Singleton();\n              }\n          }\n      }\n      return instance;\n  }\n}<\/code><\/pre>\n<\/li>\n<\/ul>\n<h2>3. <strong><code>volatile<\/code> \u7684\u5c40\u9650\u6027<\/strong><\/h2>\n<h3>3.1 <strong>\u4e0d\u4fdd\u8bc1\u539f\u5b50\u6027<\/strong><\/h3>\n<ul>\n<li>\n<p><strong>\u5b9a\u4e49<\/strong>: <code>volatile<\/code> \u4e0d\u80fd\u4fdd\u8bc1\u590d\u5408\u64cd\u4f5c\u7684\u539f\u5b50\u6027\u3002\u4f8b\u5982\uff0c<code>volatile<\/code> \u53d8\u91cf\u7684\u81ea\u589e\u64cd\u4f5c\uff08<code>count++<\/code>\uff09\u4e0d\u662f\u539f\u5b50\u64cd\u4f5c\uff0c\u56e0\u4e3a\u5b83\u6d89\u53ca\u8bfb\u53d6\u3001\u4fee\u6539\u548c\u5199\u5165\u4e09\u4e2a\u6b65\u9aa4\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u793a\u4f8b<\/strong>:<\/p>\n<pre><code class=\"language-java\">public class Counter {\n  private volatile int count;\n\n  public void increment() {\n      count++; \/\/ \u4e0d\u662f\u539f\u5b50\u64cd\u4f5c\n  }\n}<\/code><\/pre>\n<p>\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u591a\u4e2a\u7ebf\u7a0b\u540c\u65f6\u8c03\u7528 <code>increment()<\/code> \u65b9\u6cd5\u53ef\u80fd\u4f1a\u5bfc\u81f4\u6570\u636e\u4e0d\u4e00\u81f4\u3002<\/p>\n<\/li>\n<\/ul>\n<h3>3.2 <strong>\u4e0d\u80fd\u66ff\u4ee3\u9501<\/strong><\/h3>\n<ul>\n<li>\n<p><strong>\u5b9a\u4e49<\/strong>: <code>volatile<\/code> \u4e0d\u80fd\u66ff\u4ee3\u9501\uff08<code>synchronized<\/code> \u6216 <code>Lock<\/code>\uff09\uff0c\u56e0\u4e3a\u5b83\u4e0d\u80fd\u4fdd\u8bc1\u590d\u5408\u64cd\u4f5c\u7684\u539f\u5b50\u6027\u3002\u5982\u679c\u9700\u8981\u4fdd\u8bc1\u64cd\u4f5c\u7684\u539f\u5b50\u6027\uff0c\u5e94\u8be5\u4f7f\u7528\u9501\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u793a\u4f8b<\/strong>:<\/p>\n<pre><code class=\"language-java\">public class Counter {\n  private int count;\n\n  public synchronized void increment() {\n      count++; \/\/ \u4f7f\u7528 synchronized \u4fdd\u8bc1\u539f\u5b50\u6027\n  }\n}<\/code><\/pre>\n<\/li>\n<\/ul>\n<h2>4. <strong><code>volatile<\/code> \u4e0e <code>synchronized<\/code> \u7684\u533a\u522b<\/strong><\/h2>\n<h3>4.1 <strong>\u53ef\u89c1\u6027<\/strong><\/h3>\n<ul>\n<li><strong><code>volatile<\/code><\/strong>: \u786e\u4fdd\u53d8\u91cf\u7684\u4fee\u6539\u5bf9\u6240\u6709\u7ebf\u7a0b\u53ef\u89c1\u3002<\/li>\n<li><strong><code>synchronized<\/code><\/strong>: \u786e\u4fdd\u8fdb\u5165\u540c\u6b65\u5757\u7684\u7ebf\u7a0b\u80fd\u591f\u770b\u5230\u4e4b\u524d\u7ebf\u7a0b\u5bf9\u5171\u4eab\u53d8\u91cf\u7684\u4fee\u6539\u3002<\/li>\n<\/ul>\n<h3>4.2 <strong>\u6709\u5e8f\u6027<\/strong><\/h3>\n<ul>\n<li><strong><code>volatile<\/code><\/strong>: \u786e\u4fdd\u53d8\u91cf\u7684\u8bfb\u5199\u64cd\u4f5c\u5177\u6709\u4e00\u5b9a\u7684\u6709\u5e8f\u6027\u3002<\/li>\n<li><strong><code>synchronized<\/code><\/strong>: \u786e\u4fdd\u540c\u6b65\u5757\u5185\u7684\u4ee3\u7801\u6309\u987a\u5e8f\u6267\u884c\uff0c\u5e76\u4e14\u540c\u6b65\u5757\u5916\u7684\u4ee3\u7801\u4e0d\u4f1a\u88ab\u91cd\u6392\u5e8f\u5230\u540c\u6b65\u5757\u5185\u3002<\/li>\n<\/ul>\n<h3>4.3 <strong>\u539f\u5b50\u6027<\/strong><\/h3>\n<ul>\n<li><strong><code>volatile<\/code><\/strong>: \u4e0d\u80fd\u4fdd\u8bc1\u590d\u5408\u64cd\u4f5c\u7684\u539f\u5b50\u6027\u3002<\/li>\n<li><strong><code>synchronized<\/code><\/strong>: \u786e\u4fdd\u540c\u6b65\u5757\u5185\u7684\u4ee3\u7801\u662f\u539f\u5b50\u7684\u3002<\/li>\n<\/ul>\n<h1>\u5341\u4e2a\u7ebf\u7a0b\u53bbfor\u5faa\u73af +1  \u4e3a\u4ec0\u4e48countdownLanch\u65e0\u6cd5\u4fdd\u8bc1100\uff1f<\/h1>\n<p>\u5728\u591a\u7ebf\u7a0b\u73af\u5883\u4e2d\uff0c\u4f7f\u7528 <code>CountDownLatch<\/code> \u6765\u534f\u8c03\u591a\u4e2a\u7ebf\u7a0b\u7684\u6267\u884c\uff0c\u53ef\u4ee5\u786e\u4fdd\u6240\u6709\u7ebf\u7a0b\u90fd\u5b8c\u6210\u540e\u518d\u7ee7\u7eed\u6267\u884c\u4e3b\u7ebf\u7a0b\u3002\u7136\u800c\uff0c\u5373\u4f7f\u4f7f\u7528\u4e86 <code>CountDownLatch<\/code>\uff0c\u5982\u679c\u5bf9\u5171\u4eab\u53d8\u91cf\u7684\u64cd\u4f5c\u4e0d\u662f\u539f\u5b50\u7684\uff0c\u4ecd\u7136\u53ef\u80fd\u4f1a\u51fa\u73b0\u6570\u636e\u4e0d\u4e00\u81f4\u7684\u95ee\u9898\u3002<\/p>\n<h2>\u95ee\u9898\u5206\u6790<\/h2>\n<p>\u5047\u8bbe\u4f60\u6709\u4ee5\u4e0b\u4ee3\u7801\uff1a<\/p>\n<pre><code class=\"language-java\">import java.util.concurrent.CountDownLatch;\n\npublic class CountExample {\n    private static int count = 0;\n\n    public static void main(String[] args) throws InterruptedException {\n        int threadCount = 10;\n        CountDownLatch latch = new CountDownLatch(threadCount);\n\n        for (int i = 0; i &lt; threadCount; i++) {\n            new Thread(() -&gt; {\n                for (int j = 0; j &lt; 10; j++) {\n                    count++;\n                }\n                latch.countDown();\n            }).start();\n        }\n\n        latch.await();\n        System.out.println(&quot;Final count: &quot; + count);\n    }\n}<\/code><\/pre>\n<p>\u5728\u8fd9\u4e2a\u4f8b\u5b50\u4e2d\uff0c\u6bcf\u4e2a\u7ebf\u7a0b\u90fd\u4f1a\u5bf9 <code>count<\/code> \u53d8\u91cf\u8fdb\u884c 10 \u6b21\u81ea\u589e\u64cd\u4f5c\uff0c\u603b\u5171\u6709 10 \u4e2a\u7ebf\u7a0b\uff0c\u56e0\u6b64\u671f\u671b\u7684\u7ed3\u679c\u662f <code>count<\/code> \u6700\u7ec8\u4e3a 100\u3002\u7136\u800c\uff0c\u5b9e\u9645\u8fd0\u884c\u65f6\uff0c<code>count<\/code> \u7684\u503c\u53ef\u80fd\u5c0f\u4e8e 100\u3002<\/p>\n<h2>\u539f\u56e0<\/h2>\n<h3>1. <strong>\u975e\u539f\u5b50\u64cd\u4f5c<\/strong><\/h3>\n<ul>\n<li><code>count++<\/code> \u64cd\u4f5c\u4e0d\u662f\u539f\u5b50\u7684\u3002\u5b83\u5b9e\u9645\u4e0a\u5305\u542b\u4e09\u4e2a\u6b65\u9aa4\uff1a\u8bfb\u53d6 <code>count<\/code> \u7684\u503c\u3001\u589e\u52a0 <code>count<\/code> \u7684\u503c\u3001\u5c06\u589e\u52a0\u540e\u7684\u503c\u5199\u56de <code>count<\/code>\u3002<\/li>\n<li>\u5728\u591a\u7ebf\u7a0b\u73af\u5883\u4e0b\uff0c\u591a\u4e2a\u7ebf\u7a0b\u53ef\u80fd\u540c\u65f6\u8bfb\u53d6 <code>count<\/code> \u7684\u503c\uff0c\u7136\u540e\u5404\u81ea\u589e\u52a0\u5e76\u5199\u56de\uff0c\u5bfc\u81f4\u67d0\u4e9b\u589e\u52a0\u64cd\u4f5c\u4e22\u5931\u3002<\/li>\n<\/ul>\n<h3>2. <strong>\u7ebf\u7a0b\u5b89\u5168\u95ee\u9898<\/strong><\/h3>\n<ul>\n<li>\u5c3d\u7ba1 <code>CountDownLatch<\/code> \u786e\u4fdd\u4e86\u6240\u6709\u7ebf\u7a0b\u90fd\u5b8c\u6210\u4e86\u81ea\u589e\u64cd\u4f5c\uff0c\u4f46\u5b83\u4e0d\u80fd\u4fdd\u8bc1\u8fd9\u4e9b\u64cd\u4f5c\u7684\u539f\u5b50\u6027\u3002<\/li>\n<li>\u5982\u679c\u6ca1\u6709\u540c\u6b65\u673a\u5236\uff08\u5982 <code>synchronized<\/code> \u6216 <code>AtomicInteger<\/code>\uff09\uff0c\u591a\u4e2a\u7ebf\u7a0b\u53ef\u80fd\u4f1a\u5728\u540c\u4e00\u65f6\u95f4\u8bfb\u53d6\u76f8\u540c\u7684 <code>count<\/code> \u503c\uff0c\u7136\u540e\u5404\u81ea\u589e\u52a0\u5e76\u5199\u56de\uff0c\u5bfc\u81f4\u6700\u7ec8\u7ed3\u679c\u5c0f\u4e8e\u9884\u671f\u3002<\/li>\n<\/ul>\n<h2>\u89e3\u51b3\u65b9\u6848<\/h2>\n<h3>1. <strong>\u4f7f\u7528 <code>synchronized<\/code><\/strong><\/h3>\n<ul>\n<li>\n<p>\u4f7f\u7528 <code>synchronized<\/code> \u5173\u952e\u5b57\u6765\u786e\u4fdd <code>count++<\/code> \u64cd\u4f5c\u7684\u539f\u5b50\u6027\u3002<\/p>\n<\/li>\n<li>\n<p>\u793a\u4f8b\uff1a<\/p>\n<pre><code class=\"language-java\"> import java.util.concurrent.CountDownLatch;\n\n public class CountExample {\n     private static int count = 0;\n\n     public static void main(String[] args) throws InterruptedException {\n         int threadCount = 10;\n         CountDownLatch latch = new CountDownLatch(threadCount);\n\n         for (int i = 0; i < threadCount; i++) {\n             new Thread(() -> {\n                 for (int j = 0; j < 10; j++) {\n                     synchronized (CountExample.class) {\n                         count++;\n                     }\n                 }\n                 latch.countDown();\n             }).start();\n         }\n\n         latch.await();\n         System.out.println(\"Final count: \" + count);\n     }\n }<\/code><\/pre>\n<\/li>\n<\/ul>\n<h3>2. <strong>\u4f7f\u7528 <code>AtomicInteger<\/code><\/strong><\/h3>\n<ul>\n<li>\n<p>\u4f7f\u7528 <code>AtomicInteger<\/code> \u7c7b\u6765\u786e\u4fdd\u81ea\u589e\u64cd\u4f5c\u7684\u539f\u5b50\u6027\u3002<\/p>\n<\/li>\n<li>\n<p>\u793a\u4f8b\uff1a<\/p>\n<pre><code class=\"language-java\"> import java.util.concurrent.CountDownLatch;\n import java.util.concurrent.atomic.AtomicInteger;\n\n public class CountExample {\n     private static AtomicInteger count = new AtomicInteger(0);\n\n     public static void main(String[] args) throws InterruptedException {\n         int threadCount = 10;\n         CountDownLatch latch = new CountDownLatch(threadCount);\n\n         for (int i = 0; i < threadCount; i++) {\n             new Thread(() -> {\n                 for (int j = 0; j < 10; j++) {\n                     count.incrementAndGet();\n                 }\n                 latch.countDown();\n             }).start();\n         }\n\n         latch.await();\n         System.out.println(\"Final count: \" + count.get());\n     }\n }<\/code><\/pre>\n<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>MVCC \u7684\u5b9e\u73b0\u539f\u7406 \u591a\u7248\u672c\u5e76\u53d1\u63a7\u5236\uff08MVCC\uff0cMultiversion Concurrency Contro [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[11],"tags":[32],"class_list":["post-70","post","type-post","status-publish","format-standard","hentry","category-interview","tag-32"],"_links":{"self":[{"href":"https:\/\/blog.eastfond.com\/index.php?rest_route=\/wp\/v2\/posts\/70","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blog.eastfond.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.eastfond.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.eastfond.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.eastfond.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=70"}],"version-history":[{"count":15,"href":"https:\/\/blog.eastfond.com\/index.php?rest_route=\/wp\/v2\/posts\/70\/revisions"}],"predecessor-version":[{"id":426,"href":"https:\/\/blog.eastfond.com\/index.php?rest_route=\/wp\/v2\/posts\/70\/revisions\/426"}],"wp:attachment":[{"href":"https:\/\/blog.eastfond.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=70"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.eastfond.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=70"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.eastfond.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=70"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}