{"id":299,"date":"2021-01-15T14:56:44","date_gmt":"2021-01-15T06:56:44","guid":{"rendered":"https:\/\/22pig.com\/?p=299"},"modified":"2021-01-15T14:56:44","modified_gmt":"2021-01-15T06:56:44","slug":"java%e4%b8%ad%e7%9a%84%e5%8a%a8%e6%80%81%e5%8a%a0%e8%bd%bd%e5%92%8c%e7%83%ad%e6%9b%bf%e6%8d%a2","status":"publish","type":"post","link":"http:\/\/22pig.com\/?p=299","title":{"rendered":"java\u4e2d\u7684\u52a8\u6001\u52a0\u8f7d\u548c\u70ed\u66ff\u6362"},"content":{"rendered":"<p>1.C++\u7f16\u5199\u7684\u7a0b\u5e8f\u9700\u8981\u7ecf\u8fc7\u7f16\u8bd1\u79f0\u4e3a\u76ee\u6807\u6587\u4ef6\uff0c\u7136\u540e\u5728\u7a0b\u5e8f\u6267\u884c\u4e4b\u524d\u8fdb\u884c\u94fe\u63a5\u540e\u624d\u53ef\u4ee5\u79f0\u4e3a\u53ef\u4ee5\u8fd0\u884c\u7684\u53ef\u6267\u884c\u7a0b\u5e8f\uff0c\u8fd9\u4e2a\u94fe\u63a5\u53ef\u4ee5\u53d1\u751f\u5728\u7a0b\u5e8f\u8fd0\u884c\u4e4b\u524d\uff0c\u4e5f\u53ef\u4ee5\u53d1\u751f\u5728\u7a0b\u5e8f\u8fd0\u884c\u540e\uff08\u5728\u5185\u6838\u4e2d\u5b8c\u6210\u94fe\u63a5\u8fc7\u7a0b\uff09\u518d\u88ab\u6267\u884c\u3002\uff08\u8fd0\u884c\u53ef\u4ee5\u7406\u89e3\u4e3a\u53cc\u51fb\u6253\u5f00\uff09\u3002\u800cJava\u5219\u53ea\u9700\u8981\u7f16\u8bd1\u6210\u5b57\u8282\u7801\uff0c\u7136\u540e\u4ea4\u7ed9JVM\u89e3\u6790\u5668\u53bb\u94fe\u63a5\u6267\u884c\u5c31\u53ef\u4ee5\u4e86\u3002\uff08C++\u7cfb\u5217\u4e5f\u62e5\u6709\u52a8\u6001\u52a0\u8f7d\u548c\u52a8\u6001\u94fe\u63a5\u7b49\u6982\u5ff5\uff09<\/p>\n<p>2.Java\u7684\u52a8\u6001\u52a0\u8f7d\u5b9e\u9645\u4e0a\u5c31\u662f\u7a0b\u5e8f\u5728\u6267\u884c\u8fc7\u7a0b\u4e2d\u53ef\u4ee5\u6839\u636e\u7a0b\u5e8f\u8bbe\u5b9a\u53bb\u52a0\u8f7d\u9700\u8981\u88ab\u6267\u884c\u7684\u5b57\u8282\u7801\u6587\u4ef6\u3002<\/p>\n<p>3.\u70ed\u66ff\u6362\u5c5e\u4e8e\u52a8\u6001\u52a0\u8f7d\u7684\u4e00\u79cd\uff0c\u4f46\u662f\u70ed\u66ff\u6362\u662f\u7279\u6b8a\u7684\u52a8\u6001\u52a0\u8f7d\u673a\u5236\u3002<\/p>\n<p>4.\u52a8\u6001\u52a0\u8f7d\u5728Java\u4e2d\u67092\u79cd\u5b9e\u73b0\uff0c\u7b2c\u4e00\u79cd\u901a\u8fc7ClassLoader.loadClass()\u53bb\u52a0\u8f7d\uff0cClassLoader\u6700\u9ad8\u7ea7\u522b\u7684\u7c7b\u52a0\u8f7d\u5668\uff0c\u6240\u6709\u7684\u7c7b\u90fd\u5f52\u4ed6\u7ba1\u7406\uff0c\u7528loadClass\u52a0\u8f7d\u7684\u7c7b\uff0c\u662f\u672a\u7ecf\u8fc7\u521d\u59cb\u5316\u7684\uff0c\u6240\u4ee5\u5f88\u591a\u9759\u6001\u53d8\u91cf\u548c\u65b9\u6cd5\u65e0\u6cd5\u88ab\u4f7f\u7528\uff0c\u7b2c\u4e8c\u79cd\u65b9\u6cd5\u5219\u662f\uff0cClass.forName().\u7528\u8fd9\u4e2a\u65b9\u6cd5\u52a0\u8f7d\u7684\u7c7b\u5df2\u7ecf\u7ecf\u8fc7\u521d\u59cb\u5316\u3002<\/p>\n<p>5.\u800c\u5982\u4f55\u5b9e\u73b0\u70ed\u66ff\u6362\u5462\uff1f\u9996\u5148\u6211\u4eec\u8981\u77e5\u9053ClassLoader\u4e2d\u7684loadClass\u5728\u52a0\u8f7d\u7c7b\u7684\u65f6\u5019\u4f1a\u68c0\u6d4b\u8be5\u7c7b\u662f\u5426\u5df2\u7ecf\u5b58\u5728\uff0c\u5982\u679c\u5b58\u5728\u5219\u4e0d\u4f1a\u53bb\u52a0\u8f7d\uff0c\u5982\u679c\u4e0d\u5b58\u5728\u5219\u52a0\u8f7d\u8be5\u7c7b\u5e76\u7f13\u5b58\u3002\u6240\u4ee5\u9ed8\u8ba4\u7684ClassLoader\u662f\u65e0\u6cd5\u5b9e\u73b0\u70ed\u66ff\u6362\u7684\u3002\u6362\u53e5\u8bdd\u8bf4\uff0c\u8981\u5b9e\u73b0\u70ed\u66ff\u6362\u5c31\u5fc5\u987b\u5b9e\u73b0\u4e00\u4e2a\u81ea\u5df1\u7684MyClassLoader,\u5b9e\u73b0\u4e00\u4e2a\u81ea\u5df1\u7684\u7528\u4e8e\u52a0\u8f7d\u7c7b\u7684\u65b9\u6cd5findClass\uff08\uff09\uff0c\u5728\u65b9\u6cd5\u91cc\u9762\u8981\u505a\u7684\u4e8b\u60c5\u5c31\u662f\u8bfb\u53d6\u672c\u5730\u5b57\u8282\u7801\u6587\u4ef6\uff0c\u53ea\u7528\u7236\u7c7b\u7684defineClass()\u65b9\u6cd5\u53bb\u89e3\u6790\u5b83\u3002\u8fd9\u6837\u5c31\u53ef\u4ee5\u83b7\u53d6\u65b0\u7684\u7c7b\u4e86\uff0c\u800c\u65e7\u7684\u7c7b\u7531\u4e8eClassLoader\u4e0d\u53ef\u8fbe\uff0c\u6240\u4ee5\u4f1a\u88abGC\u56de\u6536\u3002<\/p>\n<p>\u4e0b\u9762\u662fMyClassLoader\u7684\u4ee3\u7801\uff1a<\/p>\n<pre>import java.io.ByteArrayOutputStream;\nimport java.io.File;\nimport java.io.FileInputStream;\nimport java.io.FileNotFoundException;\nimport java.io.IOException;\nimport java.nio.ByteBuffer;\nimport java.nio.channels.FileChannel;\n\npublic class MyClassLoader extends ClassLoader {\n    public MyClassLoader() {\n    }\n\n    public Class&lt;?&gt; findClass(String name) throws ClassNotFoundException {\n        String classPath = MyClassLoader.class.getResource(\"\/\").getPath();\n        String fileName = name.replace(\".\", \"\/\") + \".class\";\n        File classFile = new File(classPath, fileName);\n        if(!classFile.exists()) {\n            throw new ClassNotFoundException(classFile.getPath() + \" \u4e0d\u5b58\u5728\");\n        } else {\n            ByteArrayOutputStream bos = new ByteArrayOutputStream();\n            ByteBuffer bf = ByteBuffer.allocate(1024);\n            FileInputStream fis = null;\n            FileChannel fc = null;\n\n            try {\n                fis = new FileInputStream(classFile);\n                fc = fis.getChannel();\n\n                while(fc.read(bf) &gt; 0) {\n                    bf.flip();\n                    bos.write(bf.array(), 0, bf.limit());\n                    bf.clear();\n                }\n            } catch (FileNotFoundException var20) {\n                var20.printStackTrace();\n            } catch (IOException var21) {\n                var21.printStackTrace();\n            } finally {\n                try {\n                    fis.close();\n                    fc.close();\n                } catch (IOException var19) {\n                    var19.printStackTrace();\n                }\n\n            }\n\n            return this.defineClass(bos.toByteArray(), 0, bos.toByteArray().length);\n        }\n    }\n}<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>1.C++\u7f16\u5199\u7684\u7a0b\u5e8f\u9700\u8981\u7ecf\u8fc7\u7f16\u8bd1\u79f0\u4e3a\u76ee\u6807\u6587\u4ef6\uff0c\u7136\u540e\u5728\u7a0b\u5e8f\u6267\u884c\u4e4b\u524d\u8fdb\u884c\u94fe\u63a5\u540e\u624d\u53ef\u4ee5\u79f0\u4e3a\u53ef\u4ee5\u8fd0\u884c\u7684\u53ef\u6267\u884c\u7a0b\u5e8f\uff0c\u8fd9\u4e2a\u94fe\u63a5\u53ef\u4ee5\u53d1\u751f\u5728\u7a0b\u5e8f\u8fd0\u884c\u4e4b\u524d\uff0c\u4e5f\u53ef\u4ee5\u53d1\u751f\u5728\u7a0b\u5e8f\u8fd0\u884c\u540e\uff08\u5728\u5185\u6838\u4e2d\u5b8c\u6210\u94fe\u63a5\u8fc7\u7a0b\uff09\u518d\u88ab\u6267\u884c\u3002\uff08\u8fd0\u884c\u53ef\u4ee5\u7406\u89e3\u4e3a\u53cc\u51fb\u6253\u5f00\uff09\u3002\u800cJava\u5219\u53ea\u9700\u8981\u7f16\u8bd1\u6210\u5b57\u8282\u7801\uff0c\u7136\u540e\u4ea4\u7ed9JVM\u89e3\u6790\u5668\u53bb\u94fe\u63a5\u6267\u884c\u5c31\u53ef\u4ee5\u4e86\u3002\uff08C++\u7cfb\u5217\u4e5f\u62e5\u6709\u52a8\u6001\u52a0\u8f7d\u548c\u52a8\u6001\u94fe\u63a5\u7b49\u6982\u5ff5\uff09 2.Java\u7684\u52a8\u6001\u52a0\u8f7d\u5b9e\u9645\u4e0a\u5c31\u662f\u7a0b\u5e8f\u5728\u6267\u884c\u8fc7\u7a0b\u4e2d\u53ef\u4ee5\u6839\u636e\u7a0b\u5e8f\u8bbe\u5b9a\u53bb\u52a0\u8f7d\u9700\u8981\u88ab\u6267\u884c\u7684\u5b57\u8282\u7801\u6587\u4ef6\u3002 3.\u70ed\u66ff\u6362\u5c5e\u4e8e\u52a8\u6001\u52a0\u8f7d\u7684\u4e00\u79cd\uff0c\u4f46\u662f\u70ed\u66ff\u6362\u662f\u7279\u6b8a\u7684\u52a8\u6001\u52a0\u8f7d\u673a\u5236\u3002 4.\u52a8\u6001\u52a0\u8f7d\u5728Java\u4e2d\u67092\u79cd\u5b9e\u73b0\uff0c\u7b2c\u4e00\u79cd\u901a\u8fc7ClassLoader.loadClass()\u53bb\u52a0\u8f7d\uff0cClassLoader\u6700\u9ad8\u7ea7\u522b\u7684\u7c7b\u52a0\u8f7d\u5668\uff0c\u6240\u6709\u7684\u7c7b\u90fd\u5f52\u4ed6\u7ba1\u7406\uff0c\u7528loadClass\u52a0\u8f7d\u7684\u7c7b\uff0c\u662f\u672a\u7ecf\u8fc7\u521d\u59cb\u5316\u7684\uff0c\u6240\u4ee5\u5f88\u591a\u9759\u6001\u53d8\u91cf\u548c\u65b9\u6cd5\u65e0\u6cd5\u88ab\u4f7f\u7528\uff0c\u7b2c\u4e8c\u79cd\u65b9\u6cd5\u5219\u662f\uff0cClass.forName().\u7528\u8fd9\u4e2a\u65b9\u6cd5\u52a0\u8f7d\u7684\u7c7b\u5df2\u7ecf\u7ecf\u8fc7\u521d\u59cb\u5316\u3002 5.\u800c\u5982\u4f55\u5b9e\u73b0\u70ed\u66ff\u6362\u5462\uff1f\u9996\u5148\u6211\u4eec\u8981\u77e5\u9053ClassLoader\u4e2d\u7684loadClass\u5728\u52a0\u8f7d\u7c7b\u7684\u65f6\u5019\u4f1a\u68c0\u6d4b\u8be5\u7c7b\u662f\u5426\u5df2\u7ecf\u5b58\u5728\uff0c\u5982\u679c\u5b58\u5728\u5219\u4e0d\u4f1a\u53bb\u52a0\u8f7d\uff0c\u5982\u679c\u4e0d\u5b58\u5728\u5219\u52a0\u8f7d\u8be5\u7c7b\u5e76\u7f13\u5b58\u3002\u6240\u4ee5\u9ed8\u8ba4\u7684ClassLoader\u662f\u65e0\u6cd5\u5b9e\u73b0\u70ed\u66ff\u6362\u7684\u3002\u6362\u53e5\u8bdd\u8bf4\uff0c\u8981\u5b9e\u73b0\u70ed\u66ff\u6362\u5c31\u5fc5\u987b\u5b9e\u73b0\u4e00\u4e2a\u81ea\u5df1\u7684MyClassLoader,\u5b9e\u73b0\u4e00\u4e2a\u81ea\u5df1\u7684\u7528\u4e8e\u52a0\u8f7d\u7c7b\u7684\u65b9\u6cd5findClass\uff08\uff09\uff0c\u5728\u65b9\u6cd5\u91cc\u9762\u8981\u505a\u7684\u4e8b\u60c5\u5c31\u662f\u8bfb\u53d6\u672c\u5730\u5b57\u8282\u7801\u6587\u4ef6\uff0c\u53ea\u7528\u7236\u7c7b\u7684defineClass()\u65b9\u6cd5\u53bb\u89e3\u6790\u5b83\u3002\u8fd9\u6837\u5c31\u53ef\u4ee5\u83b7\u53d6\u65b0\u7684\u7c7b\u4e86\uff0c\u800c\u65e7\u7684\u7c7b\u7531\u4e8eClassLoader\u4e0d\u53ef\u8fbe\uff0c\u6240\u4ee5\u4f1a\u88abGC\u56de\u6536\u3002 \u4e0b\u9762\u662fMyClassLoader\u7684\u4ee3\u7801\uff1a import java.io.ByteArrayOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; import java.nio.ByteBuffer; import java.nio.channels.FileChannel; public class MyClassLoader extends ClassLoader { public MyClassLoader() { } public Class&lt;?&gt; findClass(String name) throws ClassNotFoundException { String classPath = MyClassLoader.class.getResource(&#8220;\/&#8221;).getPath(); String fileName = name.replace(&#8220;.&#8221;, &#8220;\/&#8221;) + &#8220;.class&#8221;; File classFile = new File(classPath, fileName); if(!classFile.exists()) &#8230; <a title=\"java\u4e2d\u7684\u52a8\u6001\u52a0\u8f7d\u548c\u70ed\u66ff\u6362\" class=\"read-more\" href=\"http:\/\/22pig.com\/?p=299\" aria-label=\"More on java\u4e2d\u7684\u52a8\u6001\u52a0\u8f7d\u548c\u70ed\u66ff\u6362\">Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[],"class_list":["post-299","post","type-post","status-publish","format-standard","hentry","category-java"],"_links":{"self":[{"href":"http:\/\/22pig.com\/index.php?rest_route=\/wp\/v2\/posts\/299","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/22pig.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/22pig.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/22pig.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/22pig.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=299"}],"version-history":[{"count":0,"href":"http:\/\/22pig.com\/index.php?rest_route=\/wp\/v2\/posts\/299\/revisions"}],"wp:attachment":[{"href":"http:\/\/22pig.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=299"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/22pig.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=299"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/22pig.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=299"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}