{"id":638,"date":"2013-12-15T16:58:18","date_gmt":"2013-12-15T08:58:18","guid":{"rendered":"http:\/\/coderbee.net\/?p=638"},"modified":"2013-12-15T17:00:51","modified_gmt":"2013-12-15T09:00:51","slug":"jvm-%e7%b1%bb%e5%8a%a0%e8%bd%bd%e6%9c%ba%e5%88%b6","status":"publish","type":"post","link":"https:\/\/coderbee.net\/index.php\/jvm\/20131215\/638","title":{"rendered":"JVM \u7c7b\u52a0\u8f7d\u673a\u5236"},"content":{"rendered":"<p>\u865a\u62df\u673a\u7c7b\u52a0\u8f7d\u673a\u5236\uff1a\u628a\u63cf\u8ff0\u7c7b\u7684\u6570\u636e\u4ececlass\u6587\u4ef6\u52a0\u8f7d\u5230\u5185\u5b58\uff0c\u5e76\u5bf9\u6570\u636e\u8fdb\u884c\u6821\u9a8c\u3001\u8f6c\u6362\u89e3\u6790\u548c\u521d\u59cb\u5316\uff0c\u6700\u7ec8\u5f62\u6210\u53ef\u4ee5\u88ab\u865a\u62df\u673a\u76f4\u63a5\u4f7f\u7528\u7684 Java \u7c7b\u578b\u3002<\/p>\n<p>\u5728Java\u8bed\u8a00\u91cc\u9762\uff0c\u7c7b\u578b\u7684\u52a0\u8f7d\u3001\u8fde\u63a5\u548c\u521d\u59cb\u5316\u90fd\u662f\u5728\u7a0b\u5e8f\u8fd0\u884c\u671f\u95f4\u5b8c\u6210\u7684\u3002<\/p>\n<h3>\u7c7b\u52a0\u8f7d\u7684\u65f6\u673a<\/h3>\n<p>\u7c7b\u7684\u6574\u4e2a\u751f\u547d\u5468\u671f\u5305\u62ec\uff1a\u52a0\u8f7d\uff08loading\uff09\u3001\u9a8c\u8bc1\uff08verification\uff09\u3001\u51c6\u5907\uff08preparation\uff09\u3001\u89e3\u6790\uff08resolution\uff09\u3001\u521d\u59cb\u5316\uff08initialization\uff09\u3001\u4f7f\u7528\uff08using\uff09\u548c\u5378\u8f7d\uff08unloading\uff09 7\u4e2a\u9636\u6bb5\u3002\u5176\u4e2d \u9a8c\u8bc1\u3001\u51c6\u5907\u3001\u89e3\u6790 3\u4e2a\u90e8\u5206\u7edf\u79f0\u8fde\u63a5\uff08linking\uff09\u3002<\/p>\n<p><img decoding=\"async\" src=\"\/\/coderbee.net\/wp-content\/uploads\/2013\/12\/class-life-cycle.png\" alt=\"class life cycle\"  \/><\/p>\n<p>5\u79cd\u5fc5\u987b\u7acb\u5373\u521d\u59cb\u5316\u7684\u60c5\u51b5\uff1a<\/p>\n<ol>\n<li>\u9047\u5230new, getstatic, putstatic \u6216 invokestatic \u8fd94\u6311\u5b57\u8282\u7801\u6307\u4ee4\uff1b<\/li>\n<li>\u4f7f\u7528 java.lang.reflect \u5305\u7684\u65b9\u6cd5\u5bf9\u7c7b\u8fdb\u884c\u53cd\u5c04\u8c03\u7528\uff1b<\/li>\n<li>\u521d\u59cb\u5316\u4e00\u4e2a\u7c7b\u7684\u65f6\u5019\uff0c\u5176\u7236\u7c7b\u8fd8\u6ca1\u6709\u521d\u59cb\u5316\uff0c\u5fc5\u987b\u5148\u89e6\u53d1\u5176\u7236\u7c7b\u7684\u521d\u59cb\u5316\uff1b\uff08\u5bf9\u4e8e\u63a5\u53e3\uff0c\u53ea\u6709\u5728\u771f\u6b63\u7528\u5230\u5176\u7236\u63a5\u53e3\u7684\u65f6\u5019\u624d\u4f1a\u521d\u59cb\u5316\uff09<\/li>\n<li>\u865a\u62df\u673a\u542f\u52a8\u65f6\uff0c\u7528\u6237\u6307\u5b9a\u8981\u6267\u884c\u7684\u4e3b\u7c7b\uff1b<\/li>\n<li>\u5f53\u4f7f\u7528 JDK 1.7 \u7684\u52a8\u6001\u8bed\u8a00\u652f\u6301\u65f6\uff0c\u5982\u679c\u4e00\u4e2a java.lang.invoke.MethodHandle \u5b9e\u4f8b\u6700\u540e\u7684\u89e3\u6790\u7ed3\u679c REF_getStatic, REF_putStatic, REF_invokeStatic \u7684\u65b9\u6cd5\u53e5\u67c4\uff0c\u5e76\u4e14\u8fd9\u4e2a\u65b9\u6cd5\u53e5\u67c4\u9501\u5bf9\u5e94\u7684\u7c7b\u6ca1\u6709\u8fdb\u884c\u51fa\u4e8b\uff0c\u5219\u9700\u8981\u5148\u89e6\u53d1\u5176\u521d\u59cb\u5316\u3002<\/li>\n<\/ol>\n<p>\u5bf9\u4e8e\u9759\u6001\u5b57\u6bb5\uff0c\u53ea\u6709\u76f4\u63a5\u5b9a\u4e49\u8fd9\u4e2a\u5b57\u6bb5\u7684\u7c7b\u624d\u4f1a\u88ab\u521d\u59cb\u5316\u3002<br \/>\n<!--more--><\/p>\n<h3>\u7c7b\u52a0\u8f7d\u8fc7\u7a0b<\/h3>\n<p>\u5728\u52a0\u8f7d\u9636\u6bb5\uff0c\u865a\u62df\u673a\u9700\u8981\u5b8c\u6210\u4ee5\u4e0b3\u4ef6\u4e8b\uff1a<\/p>\n<ol>\n<li>\u901a\u8fc7\u4e00\u4e2a\u7c7b\u7684\u5168\u9650\u5b9a\u540d\u6765\u83b7\u53d6\u5b9a\u4e49\u6b64\u7c7b\u7684\u4e8c\u8fdb\u5236\u5b57\u8282\u6d41\uff1b<\/li>\n<li>\u5c06\u8fd9\u4e2a\u5b57\u8282\u6d41\u6240\u4ee3\u8868\u7684\u9759\u6001\u5b58\u50a8\u7ed3\u6784\u8f6c\u5316\u4e3a\u65b9\u6cd5\u533a\u7684\u8fd0\u884c\u65f6\u6570\u636e\u7ed3\u6784\uff1b<\/li>\n<li>\u5728\u5185\u5b58\u4e2d\u751f\u6210\u4e00\u4e2a\u4ee3\u8868\u8fd9\u4e2a\u7c7b\u7684 java.lang.Class \u5bf9\u8c61 \uff0c\u4f5c\u4e3a\u65b9\u6cd5\u533a\u8fd9\u4e2a\u7c7b\u7684\u5404\u79cd\u6570\u636e\u7684\u8bbf\u95ee\u5165\u53e3\u3002<\/li>\n<\/ol>\n<p>\u9a8c\u8bc1\u9636\u6bb5\u5927\u81f4\u4e0a\u4f1a\u5b8c\u6210\u4e0b\u97624\u4e2a\u9636\u6bb5\u7684\u6821\u9a8c\u52a8\u4f5c\uff1a\u6587\u4ef6\u683c\u5f0f\u9a8c\u8bc1\u3001\u5143\u6570\u636e\u9a8c\u8bc1\u3001\u5b57\u8282\u7801\u9a8c\u8bc1\u3001\u7b26\u53f7\u5f15\u7528\u9a8c\u8bc1\u3002<\/p>\n<p>\u51c6\u5907\u9636\u6bb5\u6b63\u5f0f\u4e3a\u7c7b\u53d8\u91cf\u5206\u914d\u5185\u5b58\u5e76\u8bbe\u7f6e\u7c7b\u53d8\u91cf\u521d\u59cb\u503c\u3002\u5982\u679c\u7c7b\u53d8\u91cf\u662f\u975e\u5e38\u91cf\u7684\uff0c\u90a3\u4e48\u8fd9\u4e2a\u521d\u59cb\u503c\u4e00\u822c\u662f\u96f6\u503c\uff0c\u5e38\u91cf\u5219\u6839\u636eclass\u6587\u4ef6\u7684\u91cc\u7684ConstantValue\u8bbe\u7f6e\u4e3a\u76ee\u6807\u503c\u3002<\/p>\n<p>\u89e3\u6790\u9636\u6bb5\u662f\u5c06\u5e38\u91cf\u6c60\u5185\u7684\u7b26\u53f7\u5f15\u7528\u8f6c\u6362\u4e3a\u76f4\u63a5\u5f15\u7528\u7684\u8fc7\u7a0b\u3002<\/p>\n<blockquote><p>\n  \u7b26\u53f7\u5f15\u7528\uff08Symbolic References\uff09\uff1a\u7b26\u53f7\u5f15\u7528\u4ee5\u4e00\u7ec4\u7b26\u53f7\u6765\u63cf\u8ff0\u6240\u5f15\u7528\u7684\u76ee\u6807\uff0c\u7b26\u53f7\u53ef\u4ee5\u662f\u4efb\u4f55\u5f62\u5f0f\u7684\u5b57\u9762\u91cf\uff0c\u53ea\u8981\u4f7f\u7528\u65f6\u80fd\u65e0\u6b67\u4e49\u5730\u5b9a\u4f4d\u5230\u76ee\u6807\u5373\u53ef\u3002\u7b26\u53f7\u5f15\u7528\u4e0e\u865a\u62df\u673a\u7684\u5185\u5b58\u5e03\u5c40\u65e0\u5173\u3002<br \/>\n  <br \/>\n    \u76f4\u63a5\u5f15\u7528\uff08Direct Reference\uff09\uff1a\u76f4\u63a5\u5f15\u7528\u53ef\u4ee5\u662f\u76f4\u63a5\u6307\u5411\u76ee\u6807\u7684\u6307\u9488\u3001\u76f8\u5bf9\u504f\u79fb\u91cf\u6216\u662f\u4e00\u4e2a\u80fd\u95f4\u63a5\u5b9a\u4f4d\u5230\u76ee\u6807\u7684\u53e5\u67c4\u3002\u76f4\u63a5\u5f15\u7528\u4e0e\u865a\u62df\u673a\u7684\u5185\u5b58\u5e03\u5c40\u6709\u5173\u3002\u5982\u679c\u6709\u4e86\u76f4\u63a5\u5f15\u7528\uff0c\u5f15\u7528\u7684\u76ee\u6807\u5fc5\u5b9a\u5df2\u5728\u5185\u5b58\u4e2d\u3002\n<\/p><\/blockquote>\n<p>\u521d\u59cb\u5316\u9636\u6bb5\u662f\u7c7b\u52a0\u8f7d\u7684\u6700\u540e\u4e00\u6b65\uff0c\u5230\u6b64\u9636\u6bb5\u624d\u771f\u6b63\u5f00\u59cb\u6267\u884c\u7c7b\u5b9a\u4e49\u4e2d\u7684java\u7a0b\u5e8f\u4ee3\u7801\u3002\uff08\u6267\u884c\u7c7b\u6784\u9020\u5668 <code>&lt;clinit&gt;()<\/code> \u65b9\u6cd5\uff09<\/p>\n<p><code>&lt;clinit&gt;()<\/code> \u65b9\u6cd5\u662f\u7531\u7f16\u8bd1\u5668\u81ea\u52a8\u6536\u96c6\u7c7b\u4e2d\u6240\u6709\u7684\u7c7b\u53d8\u91cf\u7684\u8d4b\u503c\u52a8\u4f5c\u548c\u9759\u6001\u8bed\u53e5\u5757\uff08 <code>static{}<\/code>\uff09\u4e2d\u7684\u8bed\u53e5\u5408\u5e76\u4ea7\u751f\uff0c\u6536\u96c6\u7684\u987a\u5e8f\u7531\u8bed\u53e5\u5728\u6e90\u6587\u4ef6\u4e2d\u51fa\u73b0\u7684\u987a\u5e8f\u51b3\u5b9a\uff0c\u9759\u6001\u8bed\u53e5\u5757\u4e2d\u53ea\u80fd\u8bbf\u95ee\u5230\u5b9a\u4e49\u5728\u9759\u6001\u8bed\u53e5\u5757\u4e4b\u524d\u7684\u53d8\u91cf\uff0c\u5b9a\u4e49\u5728\u5b83\u4e4b\u540e\u7684\u53d8\u91cf\uff0c\u53ef\u4ee5\u8d4b\u503c\uff0c\u4f46\u4e0d\u80fd\u8bbf\u95ee\u3002<\/p>\n<h3>\u7c7b\u52a0\u8f7d\u5668<\/h3>\n<p>\u7c7b\u52a0\u8f7d\u5668\u7528\u4e8e\u5b8c\u6210\u201c\u901a\u8fc7\u4e00\u4e2a\u7c7b\u7684\u5168\u9650\u5b9a\u540d\u6765\u83b7\u53d6\u63cf\u8ff0\u6b64\u7c7b\u7684\u4e8c\u8fdb\u5236\u5b57\u8282\u6d41\u201d\u3002<\/p>\n<p>\u4efb\u4f55\u4e00\u4e2a\u7c7b\uff0c\u90fd\u9700\u8981\u7531\u52a0\u8f7d\u5b83\u7684\u7c7b\u52a0\u8f7d\u5668\u548c\u8fd9\u4e2a\u7c7b\u672c\u8eab\u6765\u786e\u7acb\u5176\u5728 JVM \u4e2d\u7684\u552f\u4e00\u6027\uff0c\u6bcf\u4e2a\u7c7b\u52a0\u8f7d\u5668\u90fd\u62e5\u6709\u4e00\u4e2a\u72ec\u7acb\u7684\u7c7b\u540d\u79f0\u7a7a\u95f4\u3002<\/p>\n<p>\u4eceJVM\u7684\u89d2\u5ea6\uff0c\u53ea\u5b58\u5728\u4e24\u79cd\u4e0d\u540c\u7684\u7c7b\u52a0\u8f7d\u5668\uff1a<\/p>\n<ul>\n<li>\u542f\u52a8\u7c7b\u52a0\u8f7d\u5668\uff08Bootstrap ClassLoader\uff09\uff0c\u662fJVM\u7684\u4e00\u90e8\u5206\uff1b<\/li>\n<li>\u5176\u4ed6\u6240\u6709\u7684\u7c7b\u52a0\u8f7d\u5668\uff0c\u7528Java\u8bed\u8a00\u5b9e\u73b0\uff0c\u72ec\u7acb\u4e8eJVM\uff0c\u5168\u90e8\u7ee7\u627f\u81ea <code>java.lang.ClassLoader<\/code>\u3002<\/li>\n<\/ul>\n<p>\u4ece\u5f00\u53d1\u4eba\u5458\u89d2\u5ea6\uff0c\u7a0b\u5e8f\u4f1a\u4f7f\u7528\u52303\u4e2d\u7cfb\u7edf\u63d0\u4f9b\u7684\u7c7b\u52a0\u8f7d\u5668\uff1a<\/p>\n<ul>\n<li>\u542f\u52a8\u7c7b\u52a0\u8f7d\u5668\uff08Bootstrap ClassLoader\uff09\uff1a\u8d1f\u8d23\u52a0\u8f7d\u5b58\u653e\u5728 <code>&lt;JAVA_HOME&gt;\\lib<\/code> \u76ee\u5f55\u4e2d\u7684\uff0c\u6216\u8005\u88ab <code>-Xbootclasspath<\/code> \u53c2\u6570\u6240\u6307\u5b9a\u7684\u8def\u5f84\u4e2d\u7684\uff0c\u4e14\u662f\u865a\u62df\u673a\u8bc6\u522b\u7684\uff08\u4ec5\u5b89\u88c5\u6587\u4ef6\u540d\u8bc6\u522b\uff0c\u5982 rt.jar\uff09\u7c7b\u5e93\u3002<\/li>\n<li>\u6269\u5c55\u7c7b\u52a0\u8f7d\u5668\uff08Extension ClassLoader\uff09\uff1a\u8d1f\u8d23\u52a0\u8f7d <code>&lt;JAVA_HOME&gt;\\lib\\ext<\/code> \u76ee\u5f55\u4e2d\u4e0b\u3001\u6216\u8005\u88ab <code>java.ext.dirs<\/code> \u7cfb\u7edf\u53d8\u91cf\u5236\u5b9a\u7684\u8def\u5f84\u4e0b\u7684\u6240\u6709\u7c7b\u5e93\u3002<\/li>\n<li>\u5e94\u7528\u7a0b\u5e8f\u7c7b\u52a0\u8f7d\u5668\uff08Application ClassLoader\uff09\uff1a\u8fd9\u4e2a\u7c7b\u52a0\u8f7d\u5668\u4e5f\u79f0\u4e3a\u7cfb\u7edf\u7c7b\u52a0\u8f7d\u5668\uff0c\u8d1f\u8d23\u52a0\u8f7d\u7528\u6237\u7c7b\u8def\u5f84\u4e0a\u6240\u6307\u5b9a\u7684\u7c7b\u5e93\u3002<\/li>\n<\/ul>\n<p><img decoding=\"async\" src=\"\/\/coderbee.net\/wp-content\/uploads\/2013\/12\/Parents-Delegation-Model.png\" alt=\"Parents Delegation Model\" \/><\/p>\n<p>\u4e0a\u56fe\u5c55\u793a\u7684\u5173\u7cfb\u79f0\u4e3a\u7c7b\u52a0\u8f7d\u5668\u7684\u53cc\u4eb2\u59d4\u6d3e\u6a21\u578b\uff08Parents Delegation Model\uff09\u3002<\/p>\n<p>\u53cc\u4eb2\u59d4\u6d3e\u6a21\u578b\u8981\u6c42\u9664\u4e86\u542f\u52a8\u7c7b\u52a0\u8f7d\u5668\u4e4b\u5916\uff0c\u5176\u4f59\u7684\u7c7b\u52a0\u8f7d\u5668\u90fd\u5e94\u5f53\u6709\u81ea\u5df1\u7684\u7236\u7c7b\u52a0\u8f7d\u5668\uff0c\u8fd9\u79cd\u7236\u5b50\u5173\u7cfb\u4e00\u822c\u7528\u7ec4\u5408\u5b9e\u73b0\uff1a\u4e00\u4e2a\u7c7b\u52a0\u8f7d\u5668\u6536\u5230\u7c7b\u52a0\u8f7d\u8bf7\u6c42\u65f6\uff0c\u9996\u5148\u59d4\u6258\u7ed9\u7236\u7c7b\u53bb\u52a0\u8f7d\uff0c\u7236\u7c7b\u53c8\u9012\u5f52\u5730\u59d4\u6258\u7ed9\u81ea\u5df1\u7684\u7236\u7c7b\u53bb\u52a0\u8f7d\uff0c\u53ea\u6709\u5728\u7236\u7c7b\u65e0\u6cd5\u52a0\u8f7d\u65f6\u624d\u81ea\u5df1\u5c1d\u8bd5\u53bb\u52a0\u8f7d\u3002\u53cc\u4eb2\u59d4\u6d3e\u6a21\u578b\u4e0d\u662f\u5f3a\u5236\u7684\uff0c\u53ea\u662f\u5efa\u8bae\u3002<\/p>\n<p>\u9002\u5f53\u5730\u4e0d\u9075\u5b88\u53cc\u4eb2\u59d4\u6d3e\u6a21\u578b\u53ef\u4ee5\u5b9e\u73b0\u4e00\u4e9b\u7279\u6b8a\u7684\u7c7b\u52a0\u8f7d\u9700\u6c42\uff0c\u6bd4\u5982\u70ed\u90e8\u7f72\u3002<\/p>\n<hr\/>\n<p>\u6b22\u8fce\u5173\u6ce8\u6211\u7684\u5fae\u4fe1\u516c\u4f17\u53f7: <strong>coderbee\u7b14\u8bb0<\/strong>\uff0c\u53ef\u4ee5\u66f4\u53ca\u65f6\u56de\u590d\u4f60\u7684\u8ba8\u8bba\u3002<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" width=\"258\" height=\"258\" src=\"https:\/\/coderbee.net\/wp-content\/uploads\/2019\/01\/coderbee-note.jpg\" class=\"alignnone size-full wp-image-1707\"><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u865a\u62df\u673a\u7c7b\u52a0\u8f7d\u673a\u5236\uff1a\u628a\u63cf\u8ff0\u7c7b\u7684\u6570\u636e\u4ececlass\u6587\u4ef6\u52a0\u8f7d\u5230\u5185\u5b58\uff0c\u5e76\u5bf9\u6570\u636e\u8fdb\u884c\u6821\u9a8c\u3001\u8f6c &hellip; <a href=\"https:\/\/coderbee.net\/index.php\/jvm\/20131215\/638\">\u7ee7\u7eed\u9605\u8bfb <span 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