{"id":76,"date":"2015-12-04T19:30:38","date_gmt":"2015-12-04T11:30:38","guid":{"rendered":"http:\/\/www.prayerlaputa.com\/?p=76"},"modified":"2015-12-04T19:30:38","modified_gmt":"2015-12-04T11:30:38","slug":"76","status":"publish","type":"post","link":"http:\/\/prayerlaputa.com\/?p=76","title":{"rendered":"BCEL\u7b80\u660e\u6559\u7a0b"},"content":{"rendered":"<p>\u6ce8\u610f\uff1a\u672c\u6587\u7ae0\u4e3b\u8981\u4f9d\u636e<a href=\"http:\/\/commons.apache.org\/bcel\/manual.html\">BCEL\u5b98\u65b9\u624b\u518c<\/a>\u8fdb\u884c\u9610\u8ff0\uff0c\u5927\u90e8\u5206\u5185\u5bb9\u90fd\u662f\u4ece\u8be5\u624b\u518c\u76f4\u63a5\u7ffb\u8bd1\u8fc7\u6765\u7684\uff0c\u5e76\u505a\u4e86\u4e00\u5b9a\u7684\u7b80\u5316\uff0c\u540c\u65f6\u8fd8\u53c2\u8003\u4e86\u300a\u6df1\u5165\u7406\u89e3Java\u865a\u62df\u673a\u300b\uff08\u5468\u5fd7\u660e\u8457\uff09\u3002\u7b14\u8005\u5728\u4e0b\u9762\u9610\u8ff0\u7684\u65f6\u5019\u4e5f\u4f1a\u7ed9\u51fa\u76f8\u5e94\u7684\u7ae0\u8282\uff0c\u5982\u679c\u8bfb\u8005\u6709\u4e0d\u6e05\u695a\u7684\u5730\u65b9\u8bf7\u53c2\u8003<a href=\"http:\/\/commons.apache.org\/bcel\/manual.html\">BCEL\u5b98\u65b9\u624b\u518c<\/a>\u6216\u662f<a href=\"http:\/\/commons.apache.org\/bcel\/apidocs\/index.html\">BCEL API<\/a>\uff0c\u4ee5\u53ca\u300a\u6df1\u5165\u7406\u89e3Java\u865a\u62df\u673a\u300b\u3002<\/p>\n<h2><strong>BCEL\u662f\u4ec0\u4e48\uff1f<\/strong><\/h2>\n<p>\u76f8\u4fe1\u641c\u7d22\u5230\u8fd9\u7bc7\u6587\u7ae0\u7684\u8bfb\u8005\u5e94\u8be5\u77e5\u9053BCEL\u662f\u5565\uff0c\u4e0d\u8fc7\u8fd8\u662f\u7b80\u8981\u63d0\u4e00\u4e0b\u5427\uff1aBCEL\uff08Byte Code Engineering Library\uff09\u539f\u672c\u662fApache Jakarta\u7684\u4e00\u4e2a\u5b50\u9879\u76ee\uff0c\u76ee\u524d\u5df2\u6210\u4e3aApache Commons\u7684\u4e00\u4e2a\u5b50\u9879\u76ee\uff0c\u4e3b\u8981\u7528\u4e8e\u5206\u6790\u3001\u521b\u5efa\u3001\u64cd\u7eb5Java \u00a0class\u6587\u4ef6\u3002<!--more--><br \/>\n\u4e3a\u4e86\u8bf4\u660e\u5982\u4f55\u4f7f\u7528BCEL\uff0c\u9700\u8981\u7b80\u8981\u4ecb\u7ecd\u4e00\u4e0bJVM\u7ed3\u6784\u548cclass\u6587\u4ef6\u7684\u7ed3\u6784\u3002<span id=\"more-385\"><\/span><\/p>\n<h2><strong>JVM\u7ed3\u6784<\/strong><\/h2>\n<p><a href=\"http:\/\/www.prayerlaputa.com\/wp-content\/uploads\/2015\/12\/JVM.png\"><img loading=\"lazy\" class=\"size-medium wp-image-80 aligncenter\" src=\"http:\/\/www.prayerlaputa.com\/wp-content\/uploads\/2015\/12\/JVM-300x152.png\" alt=\"JVM\" width=\"300\" height=\"152\" \/><\/a><br \/>\nJVM\u662fJava\u63d0\u4f9b\u5e73\u53f0\u65e0\u5173\u6027\u7684\u57fa\u7840\uff0c\u5b83\u662f\u4e00\u53f0\u62bd\u8c61\u7684\u673a\u5668\uff0c\u4e3b\u8981\u4efb\u52a1\u662f\u88c5\u8f7dclass\u6587\u4ef6\u5e76\u4e14\u6267\u884c\u5176\u4e2d\u7684\u5b57\u8282\u7801\u3002Java\u865a\u62df\u673a\u7684\u4f53\u7cfb\u7ed3\u6784\u5982\u4e0a\u56fe\u6240\u793a\u3002\u8fd9\u91cc\u4ec5\u7ed9\u51faJVM\u4e2d\u6bd4\u8f83\u91cd\u8981\u7684\u90e8\u5206\u7684\u8bf4\u660e\uff0c\u8be6\u7ec6\u4ecb\u7ecd\u8bf7\u53c2\u8003\u300a\u6df1\u5165\u7406\u89e3Java\u865a\u62df\u673a\u300b\uff08\u5468\u5fd7\u660e\u8457\uff09\u548c\u300aJava Virtual Machiine Specification\u300b\uff08\u53c2\u89c1Oracle\u7f51\u7ad9\uff09\u3002<\/p>\n<ul>\n<li><strong>\u7c7b\u88c5\u8f7d\u5b50\u7cfb\u7edf<\/strong>\uff1a\u6bcf\u4e2aJava\u865a\u62df\u673a\u90fd\u6709\u4e00\u4e2a\u7c7b\u88c5\u8f7d\u5b50\u7cfb\u7edf\uff0c\u5b83\u6839\u636e\u7ed9\u5b9a\u7684\u5168\u9650\u5b9a\u540d\u6765\u88c5\u5165\u7c7b\u6216\u63a5\u53e3\u3002<\/li>\n<li><strong>\u8fd0\u884c\u65f6\u6570\u636e\u533a<\/strong>\uff1a\u7528\u4e8e\u7ec4\u7ec7\u9700\u8981\u5185\u5b58\u6765\u5b58\u50a8\u7684\u4e1c\u897f\uff0c\u5982\uff0c\u5b57\u8282\u7801\uff0c\u7a0b\u5e8f\u521b\u5efa\u7684\u5bf9\u8c61\uff0c\u4f20\u9012\u7ed9\u65b9\u6cd5\u7684\u53c2\u6570\uff0c\u8fd4\u56de\u503c\uff0c\u5c40\u90e8\u53d8\u91cf\uff0c\u8fd0\u7b97\u7684\u4e2d\u95f4\u7ed3\u679c\uff0c\u2026\u2026<\/li>\n<li><strong>Java\u5806<\/strong>\uff1a\u5b58\u653e\u8fd0\u884c\u65f6\u521b\u5efa\u7684\u5bf9\u8c61\u5b9e\u4f8b\uff0c\u4ee5\u53ca\u5bf9\u8c61\u95f4\u7684\u5f15\u7528\u5173\u7cfb<\/li>\n<li><strong>Java\u6808<\/strong>\uff1a\u5176\u5b9e\u66f4\u51c6\u786e\u7684\u79f0\u547c\u5e94\u8be5\u662f\u201cJava Virtual Machine Stack\u201d\uff0c\u6bcf\u5f53\u4e00\u4e2a\u65b9\u6cd5\u88ab\u6267\u884c\u7684\u65f6\u5019\uff0c\u90fd\u4f1a\u521b\u5efa\u4e00\u4e2aJava\u6808\u5e27\uff08stack frame\uff09\uff0c\u6808\u5e27\u4e2d\u4fdd\u5b58\u7740\u8be5\u65b9\u6cd5\u7684\u64cd\u4f5c\u6570\u6808\u3001\u5c40\u90e8\u53d8\u91cf\u8868\uff08local variable table\uff09\u3001\u52a8\u6001\u94fe\u63a5\u3001\u65b9\u6cd5\u51fa\u53e3\u7b49\u4fe1\u606f\uff0c\u6808\u5e27\u521b\u5efa\u540e\u5c31\u4f1a\u653e\u5230Java\u6808\u4e0a\uff0c\u6267\u884c\u5b8c\u6bd5\u540e\u629b\u5f03\u8be5\u6808\u5e27\u3002\u6211\u4eec\u5e73\u65f6\u6240\u8bf4\u7684\u65b9\u6cd5\u5185\u7684\u5c40\u90e8\u53d8\u91cf\u4fdd\u5b58\u5728\u201c\u6808\u201d\u4e0a\u5176\u5b9e\u5c31\u662f\u6307Java\u6808\u3002<\/li>\n<li><strong>\u65b9\u6cd5\u533a<\/strong>\uff1a\u4fdd\u5b58\u88ab\u865a\u62df\u673a\u52a0\u8f7d\u7684\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\u3002\u6ce8\u610f\u65b9\u6cd5\u533a\u4e2d\u5305\u542b\u6709\u4e00\u4e2a<strong>\u8fd0\u884c\u533a\u5e38\u91cf\u6c60<\/strong>\uff0cclass\u6587\u4ef6\u4e2d\u7684<strong>\u5e38\u91cf\u6c60<\/strong>\uff08\u5c06\u5728\u540e\u9762\u8bb2\u89e3\uff09\u4e2d\u7684\u5185\u5bb9\u5c06\u5728\u7c7b\u52a0\u8f7d\u540e\u5b58\u653e\u5230\u8fd9\u4e2a\u8fd0\u884c\u65f6\u5e38\u91cf\u6c60\u4e2d\u3002<\/li>\n<li><strong>\u7a0b\u5e8f\u8ba1\u6570\u5668<\/strong>\uff08PC\u8ba1\u6570\u5668\uff09\uff1aPC\u5bc4\u5b58\u5668\u7684\u503c\u603b\u662f\u6307\u793a\u4e0b\u4e00\u6761\u5c06\u88ab\u6267\u884c\u7684\u6307\u4ee4<\/li>\n<li><strong>\u672c\u5730\u65b9\u6cd5\u6808<\/strong>\uff1a\u7528\u4e8e\u672c\u5730\u65b9\u6cd5\u7684\u6267\u884c\uff0c\u672c\u5730\u65b9\u6cd5\u53c2\u8003\u300aCore Java\u300b\u4e2d\u6709\u5173JNI\u7684\u9610\u8ff0\u3002<\/li>\n<\/ul>\n<h2><strong>Java class\u6587\u4ef6\u683c\u5f0f<\/strong><\/h2>\n<p>\u6ce8\uff1a\u8981\u5b8c\u6574\u7684\u8bf4\u660eclass\u6587\u4ef6\u7684\u7ed3\u6784\u662f\u4e2a\u975e\u5e38\u8d39\u52b2\u7684\u4e8b\u60c5\uff0cJVM\u6307\u4ee4\u7cfb\u7edf\u66f4\u662f\u5982\u6b64\u3002\u9650\u4e8e\u7bc7\u5e45\u8fd9\u91cc\u4e0d\u518d\u8be6\u7ec6\u9610\u8ff0\uff0c\u4ec5\u7ed9\u51fa\u7b80\u8981\u7684\u8bf4\u660e\uff0c\u8be6\u7ec6\u8bf4\u660e\u8bf7\u53c2\u8003\u300a\u6df1\u5165\u7406\u89e3Java\u865a\u62df\u673a\u300b\u548c\u300aJava Virtual Machiine Specification\u300b<br \/>\nclass\u6587\u4ef6\u7684\u683c\u5f0f\u5927\u4f53\u5982\u4e0b\u56fe\u6240\u793a<br \/>\n<a href=\"http:\/\/www.prayerlaputa.com\/wp-content\/uploads\/2015\/12\/classfile.gif\"><img loading=\"lazy\" class=\"size-medium wp-image-77 aligncenter\" src=\"http:\/\/www.prayerlaputa.com\/wp-content\/uploads\/2015\/12\/classfile-300x265.gif\" alt=\"classfile\" width=\"300\" height=\"265\" \/><\/a><a href=\"http:\/\/www.prayer-laputa.com\/blog\/wp-content\/uploads\/2013\/02\/classfile.gif\"><br \/>\n<\/a>class\u6587\u4ef6\u7684header\u90e8\u5206\u5305\u542b\u6709\u4e00\u4e2a\u201c\u9b54\u6570\u201d\uff08magic number\uff090xCAFEBABE\uff08\u5176\u5b9e\u662f\u201dcafe baby\u201d\uff0c\u6b64\u4e43\u5f53\u5e74Java\u5f00\u53d1\u56e2\u961f\u7684\u5e7d\u9ed8\uff09\uff0c\u7136\u540e\u662f\u7248\u672c\u53f7\uff0c\u518d\u4e4b\u540e\u662f\u5e38\u91cf\u6c60\uff0c\u8bbf\u95ee\u6743\u9650\u6807\u5fd7\u4f4d\uff0c\u5f53\u524d\u7c7b\uff08\u6ce8\u610f\uff0c\u8fd9\u91cc\u7684\u7c7b\u662f\u6307\u7c7b\u548c\u63a5\u53e3\uff0c\u662f\u6bd4\u8f83\u6cdb\u6cdb\u7684\u6982\u5ff5\uff0c\u4e0b\u6587\u540c\uff09\u6240\u5b9e\u73b0\u7684\u63a5\u53e3\u5217\u8868\uff0c\u5f53\u524d\u7c7b\u6240\u5305\u542b\u7684\u57df\u3001\u65b9\u6cd5\uff0c\u6700\u540e\u662f\u5f53\u524d\u7c7b\u7684\u5c5e\u6027\uff08\u53ef\u4ee5\u5305\u542b\u7528\u6237\u81ea\u5b9a\u4e49\u7684\u6570\u636e\uff09\u3002<br \/>\n\u7531\u4e8e\u9700\u8981\u5728\u8fd0\u884c\u65f6\u52a8\u6001\u89e3\u6790\u7684\u7c7b\u3001\u57df\u3001\u65b9\u6cd5\u7684\u7b26\u53f7\u5f15\u7528\u5b9e\u9645\u90fd\u662f\u4ee5\u5b57\u7b26\u4e32\u5e38\u91cf\u7684\u5f62\u5f0f\u4fdd\u5b58\u5728\u5e38\u91cf\u6c60\u4e2d\uff0c\u6240\u4ee5\u5e38\u91cf\u6c60\u5b9e\u9645\u4e0a\u5360\u4e86class\u6587\u4ef6\u7684\u5f88\u5927\u6bd4\u91cd\uff0c\u4e00\u822c\u662f60%\uff0c\u800cbyte code\u4e00\u822c\u53ea\u536012%\u3002<br \/>\n\u5e38\u91cf\u6c60\u4e2d\u4e00\u822c\u5305\u542b\u6709\u5982\u4e0b\u7c7b\u578b\u7684\u5e38\u91cf\uff1aReferences to methods, fields and classes, strings, integers, floats, longs, and doubles.\uff08\u4ee5\u4e0a\u53c2\u8003 2.1 java class file format\uff09<br \/>\n\u6ce8\u610f\uff0cclass\u6587\u4ef6\u4e2d\uff0c\u975e\u62bd\u8c61\u65b9\u6cd5\u5305\u542b\u6709\u4e00\u4e2a\u5c5e\u6027\u201cCode\u201d\uff0c\u5305\u542b\u6709\u6808\u5e27\u6240\u9700\u7684\u6700\u5927\u6df1\u5ea6\u3001\u5c40\u90e8\u53d8\u91cf\u7684\u4e2a\u6570\u3001byte code\u6307\u4ee4\u7684\u6570\u7ec4\u3002\u5f53\u5728\u65b9\u6cd5\u6267\u884c\u8fc7\u7a0b\u4e2d\u53d1\u751f\u5f02\u5e38\u65f6\uff0cJVM\u4f1a\u67e5\u627e\u5f02\u5e38\u8868\uff08table of exception handlers\uff09\uff0c\u8be5\u8868\u6807\u8bb0\u4e86handler\uff0c\u4e5f\u5c31\u662f\u54ea\u4e9b\u5f02\u5e38\u5904\u7406\u4ee3\u7801\u8d1f\u8d23\u5904\u7406\u5177\u4f53\u54ea\u4e2a\u90e8\u5206\u4ee3\u7801\u6240\u629b\u51fa\u7684\u5f02\u5e38\uff0c\u5982\u679c\u6ca1\u6709\u5408\u9002\u7684handler\uff0c\u5f02\u5e38\u5c06\u4f1a\u4f20\u9012\u7ed9\u8be5\u65b9\u6cd5\uff08callee\uff09\u7684\u8c03\u7528\u8005\uff08caller\uff09\u3002handler\u7684\u4fe1\u606f\u4fdd\u5b58\u5728\u201cCode\u201d\u5c5e\u6027\u4e2d\u3002\uff082.3 Method Code\uff09<\/p>\n<h2><strong>\u5b9e\u4f8b\u5206\u6790<\/strong><\/h2>\n<p>\uff08\u8fd9\u4e00\u90e8\u5206\u53c2\u80032.6 Code Example\uff09<br \/>\n\u9996\u5148\u7ed3\u5408\u4e0a\u8ff0\u7684\u5185\u5bb9\uff0c\u5206\u6790\u4ee5\u4e0bJava\u4ee3\u7801\u7f16\u8bd1\u540e\u6240\u5f97\u5230\u7684class\u6587\u4ef6\u3002\uff08\u5c06\u5c31\u7740\u770b\u5427\uff0cwordpress\u91cc\u4e00\u884c\u884c\u8c03\u4ee3\u7801\u7f29\u8fdb\u5b9e\u5728\u592a\u9ebb\u70e6\uff0c\u5c31\u6ca1\u600e\u4e48\u8c03\u6574~~\uff09<\/p>\n<pre class=\"brush: java; title: ; notranslate\" title=\"\"> \u00a0 \u00a0 import java.io.*;\npublic class Factorial {\n \u00a0 \u00a0 \u00a0 private static BufferedReader in = new BufferedReader(new\n \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 InputStreamReader(System.in));\npublic static final int fac(int n) {\n \u00a0 \u00a0 \u00a0 \u00a0 return (n == 0)? 1 : n * fac(n - 1);\n \u00a0 \u00a0 \u00a0 }\npublic static final int readInt() {\n \u00a0 \u00a0 \u00a0 \u00a0 int n = 4711;\n \u00a0 \u00a0 \u00a0 \u00a0 try {\n \u00a0 \u00a0 \u00a0 \u00a0 System.out.print(&amp;quot;Please enter a number&amp;gt; &amp;quot;);\n \u00a0 \u00a0 \u00a0 \u00a0 n = Integer.parseInt(in.readLine());\n \u00a0 \u00a0 \u00a0 \u00a0 } catch(IOException e1) { System.err.println(e1); }\n \u00a0 \u00a0 \u00a0 \u00a0 catch(NumberFormatException e2) { System.err.println(e2); }\n \u00a0 \u00a0 \u00a0 \u00a0 return n;\n \u00a0 \u00a0 \u00a0 }\npublic static void main(String[] argv) {\n \u00a0 \u00a0 \u00a0 \u00a0 int n = readInt();\n \u00a0 \u00a0 \u00a0 \u00a0 System.out.println(&amp;quot;Factorial of &amp;quot; + n + &amp;quot; is &amp;quot; + fac(n));\n \u00a0 \u00a0 \u00a0 }\n \u00a0 \u00a0 }\n<\/pre>\n<p>fac()\u65b9\u6cd5\u5bf9\u5e94\u7684\u5b57\u8282\u7801\u5982\u4e0b\uff1a<br \/>\n&nbsp;<\/p>\n<pre class=\"brush: java; title: ; notranslate\" title=\"\">0: \u00a0iload_0\n1: \u00a0ifne \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0#8\n4: \u00a0iconst_1\n5: \u00a0goto \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0#16\n8: \u00a0iload_0\n9: \u00a0iload_0\n10: iconst_1\n11: isub\n12: invokestatic \u00a0 \u00a0Factorial.fac (I)I (12)\n15: imul\n16: ireturn\nLocalVariable(start_pc = 0, length = 16, index = 0:int n)\n<\/pre>\n<p>\u6bcf\u6761\u6307\u4ee4\u7684\u529f\u80fd\u8fd9\u91cc\u5c31\u4e0d\u7ec6\u8bf4\uff0c\u9700\u8981\u6ce8\u610f\u7684\u662f\uff0cJVM\u662f\u4e00\u79cd\u57fa\u4e8e\u6808\u7684\u865a\u62df\u673a\uff0c\u4efb\u4f55\u64cd\u4f5c\u90fd\u9700\u8981\u5148\u5c06\u64cd\u4f5c\u6570\u653e\u5165\u6808\u5e27\u4e2d\u7684\u64cd\u4f5c\u6570\u6808\uff0c\u7136\u540e\u8c03\u7528\u76f8\u5173\u65b9\u6cd5\uff0c\u64cd\u4f5c\u7684\u7ed3\u679c\u4e5f\u4f1a\u81ea\u52a8\u7684\u538b\u5165\u64cd\u4f5c\u6570\u6808\u3002\u5728\u672c\u4f8b\u4e2d\uff0cfac()\u65b9\u6cd5\u91c7\u7528\u4e86\u9012\u5f52\u7684\u65b9\u5f0f\u8ba1\u7b97n!\uff0c\u7b2c12\u884c\u4f53\u73b0\u4e86\u8fd9\u4e00\u70b9\uff0c\u5728JVM\u6267\u884c\u5230\u5e9512\u884c\u65f6\uff0c\u4f1a\u521b\u5efa\u4e00\u4e2a\u65b0\u7684\u6808\u5e27\uff0c\u4ee5\u6267\u884c\u65b0\u7684fac()\u65b9\u6cd5\u8c03\u7528\u3002\u6b64\u5916\uff0cireturn\u4f1a\u5c06\u7ed3\u679c\u8fd4\u56de\u7ed9\u5f53\u524d\u65b9\u6cd5\uff08callee\uff09\u7684\u8c03\u7528\u8005\uff08caller\uff09\uff0c\u538b\u5165\u5230caller\u6808\u5e27\u4e2d\u64cd\u4f5c\u6570\u6808\u7684\u6808\u9876\u3002<br \/>\nreadInt()\u65b9\u6cd5\u7684\u5b57\u8282\u7801\u5982\u4e0b\uff1a<br \/>\n&nbsp;<\/p>\n<pre class=\"brush: java; title: ; notranslate\" title=\"\"> \u00a0 \u00a00: \u00a0sipush \u00a0 \u00a0 \u00a0 \u00a04711\n 3: \u00a0istore_0\n 4: \u00a0getstatic \u00a0 \u00a0 java.lang.System.out Ljava\/io\/PrintStream;\n 7: \u00a0ldc \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 &amp;quot;Please enter a number&amp;gt; &amp;quot;\n 9: \u00a0invokevirtual java.io.PrintStream.print (Ljava\/lang\/String;)V\n 12: getstatic \u00a0 \u00a0 Factorial.in Ljava\/io\/BufferedReader;\n 15: invokevirtual java.io.BufferedReader.readLine ()Ljava\/lang\/String;\n 18: invokestatic \u00a0java.lang.Integer.parseInt (Ljava\/lang\/String;)I\n 21: istore_0\n 22: goto \u00a0 \u00a0 \u00a0 \u00a0 \u00a0#44\n 25: astore_1\n 26: getstatic \u00a0 \u00a0 java.lang.System.err Ljava\/io\/PrintStream;\n 29: aload_1\n 30: invokevirtual java.io.PrintStream.println (Ljava\/lang\/Object;)V\n 33: goto \u00a0 \u00a0 \u00a0 \u00a0 \u00a0#44\n 36: astore_1\n 37: getstatic \u00a0 \u00a0 java.lang.System.err Ljava\/io\/PrintStream;\n 40: aload_1\n 41: invokevirtual java.io.PrintStream.println (Ljava\/lang\/Object;)V\n 44: iload_0\n 45: ireturn\nException handler(s) =\n From \u00a0 \u00a0To \u00a0 \u00a0 \u00a0Handler Type\n 4 \u00a0 \u00a0 \u00a0 22 \u00a0 \u00a0 \u00a025 \u00a0 \u00a0 \u00a0java.io.IOException(6)\n 4 \u00a0 \u00a0 \u00a0 22 \u00a0 \u00a0 \u00a036 \u00a0 \u00a0 \u00a0NumberFormatException(10)\n<\/pre>\n<p>\u8fd9\u4e2a\u4f8b\u5b50\u9700\u8981\u8bf4\u660e\u7684\u662f\uff0c\u5e73\u65f6\u6211\u4eec\u8c03\u7528System.out.println()\u6253\u5370\u8f93\u51fa\u65f6\uff0c\u867d\u7136\u53ea\u662f\u4f20\u5165\u8981\u6253\u5370\u7684\u5185\u5bb9\uff0c\u4f46\u5728\u5b57\u8282\u7801\u5c42\u6b21\u4e0a\uff0c\u9996\u5148\u9700\u8981\u5c06System\u7c7b\u7684\u9759\u6001\u53d8\u91cfout\u538b\u5165\u5230\u6808\u9876\uff0c\u7136\u540e\u5c06\u9700\u8981\u6253\u5370\u7684\u5185\u5bb9\uff08\u8fd9\u91cc\u662f\u5b57\u7b26\u4e32\u201c\u201dPlease enter a number&gt;\u201d\uff09\u538b\u5165\u6808\uff0c\u63a5\u7740\u8c03\u7528println()\u65b9\u6cd5\u3002\u4e4b\u6240\u4ee5\u9700\u8981\u5c06out\u538b\u5165\u6808\uff0c\u662f\u56e0\u4e3a\u5b9e\u4f8b\u65b9\u6cd5\u8c03\u7528\u7684\u65f6\u5019\uff0c\u90fd\u4f1a\u5c06\u8be5\u5b9e\u529b\u5bf9\u8c61\u7684\u5f15\u7528\u9690\u5f0f\u5730\u4f5c\u4e3a\u7b2c\u4e00\u4e2a\u53c2\u6570\uff08Instance methods always implicitly take an instance reference as their first argument\uff09\u3002<br \/>\n\u53e6\u5916\uff0cJava\u4ee3\u7801\u4e2d\u7684\u5f02\u5e38\u5904\u7406\u4ee3\u7801\uff0ctry\u8bed\u53e5\u4e0d\u4f1a\u4ea7\u751f\u4efb\u4f55\u5b9e\u9645\u4ee3\u7801\uff0c\u53ea\u662f\u89c4\u5b9a\u4e86exception handler\u5728\u54ea\u4e9b\u4ee3\u7801\u53d1\u751f\u5f02\u5e38\u65f6\u4f1a\u88ab\u8c03\u7528\u3002<\/p>\n<h2>BCEL API<\/h2>\n<p>BCEL API\u4e3b\u8981\u5206\u4e3a\u4ee5\u4e0b3\u4e2a\u90e8\u5206\uff083. The BCEL API\uff09\uff1a<\/p>\n<ul>\n<li>bcel.classfile.*\uff1a\u4e3b\u8981\u7528\u4e8e\u67e5\u770bclass\u6587\u4ef6\u7684\u7ed3\u6784\uff08\u5c24\u5176\u662f\u5728\u6ca1\u6709\u6e90\u4ee3\u7801\u7684\u60c5\u51b5\u4e0b\uff09\uff0c\u4e00\u822c\u4e0d\u7528\u4f5cbyte code\u7684\u4fee\u6539\u3002<\/li>\n<li>bcel.generic.*\uff1a\u52a8\u6001\u4ea7\u751f\u6216\u662f\u4fee\u6539class\u6587\u4ef6\uff0c\u53ef\u4ee5\u63d2\u5165\u4ee3\u7801\u3001\u4ececlass\u6587\u4ef6\u4e2d\u5254\u9664\u65e0\u7528\u4ee3\u7801\u3001\u5b9e\u73b0\u4e00\u4e2aJava\u7f16\u8bd1\u5668\u7684\u4ee3\u7801\u751f\u6210\u5668\u540e\u7aef\u3002<\/li>\n<li>\u5176\u4ed6\uff1a\u4ee3\u7801\u793a\u4f8b\uff0c\u4f7f\u7528\u5de5\u5177<\/li>\n<\/ul>\n<p>bcel.classfile.*\u7684\u7c7b\u8bbe\u8ba1\u5982\u4e0b\u56fe\uff1a<br \/>\n<a href=\"http:\/\/www.prayerlaputa.com\/wp-content\/uploads\/2015\/12\/javaclass.gif\"><img loading=\"lazy\" class=\"size-medium wp-image-79 aligncenter\" src=\"http:\/\/www.prayerlaputa.com\/wp-content\/uploads\/2015\/12\/javaclass-300x168.gif\" alt=\"javaclass\" width=\"300\" height=\"168\" \/><\/a><br \/>\n\u901a\u8fc7\u4e0b\u9762\u7684\u4ee3\u7801\uff0c\u5373\u53ef\u8bbf\u95ee\u4e00\u4e2aclass\u6587\u4ef6\u7684JavaClass\u5bf9\u8c61\uff0c\u7136\u540e\u901a\u8fc7\u8fd9\u4e2a\u5bf9\u8c61\u7684get\/set\u65b9\u6cd5\uff0c\u5373\u53ef\u8bbf\u95ee\u8fd9\u4e2aclass\u6587\u4ef6\u7684\u5404\u4e2a\u90e8\u5206\uff1a<\/p>\n<pre class=\"brush: java; title: ; notranslate\" title=\"\">JavaClass clazz = Repository.lookupClass(&amp;quot;java.lang.String&amp;quot;);\n<\/pre>\n<p>\u6bd4\u5982\u8bf4\uff0c\u4e0b\u9762\u7684printCode()\u5c31\u80fd\u8f93\u51faString\u7c7b\u7684\u6240\u6709\u65b9\u6cd5\uff1a<br \/>\n&nbsp;<\/p>\n<pre class=\"brush: java; title: ; notranslate\" title=\"\">System.out.println(clazz);\n printCode(clazz.getMethods());\n...\npublic static void printCode(Method[] methods) {\nfor(int i=0; i &amp;lt; methods.length; i++) {\nSystem.out.println(methods[i]);\nCode code = methods[i].getCode();\nif(code != null) \/\/ Non-abstract method\nSystem.out.println(code);\n}\n}\n<\/pre>\n<p><strong>3.3 ClassGen<\/strong><br \/>\nbcel.generic.*\u7684\u7c7b\u8bbe\u8ba1\u5982\u4e0b\u56fe\uff1a<br \/>\n<a href=\"http:\/\/www.prayerlaputa.com\/wp-content\/uploads\/2015\/12\/classgen.gif\"><img loading=\"lazy\" class=\"size-medium wp-image-78 aligncenter\" src=\"http:\/\/www.prayerlaputa.com\/wp-content\/uploads\/2015\/12\/classgen-300x191.gif\" alt=\"classgen\" width=\"300\" height=\"191\" \/><\/a><br \/>\n\u8981\u521b\u5efa\u4e00\u4e2a\u7c7b\uff0c\u9700\u8981\u4f7f\u7528ClassGen\uff0c\u800c\u8981\u7ed9\u8fd9\u4e2a\u7c7b\u6dfb\u52a0\u5176\u4ed6\u90e8\u5206\uff0c\u5219\u9700\u8981\u4f7f\u7528\u4e0a\u56fe\u4e2d\u7ed9\u51fa\u7684\u5176\u4ed6\u7c7b\u3002\u5728\u7ed9\u51fa\u5177\u4f53\u5b9e\u4f8b\u4e4b\u524d\uff0c\u8fd8\u9700\u8981\u5148\u786e\u5b9a\u5982\u4f55\u8868\u793a\u7c7b\u578b\u2014\u2014\u57df\u9700\u8981\u6307\u660e\u5176\u7c7b\u578b\uff0c\u65b9\u6cd5\u5219\u9700\u8981\u7ed9\u51fa\u53c2\u6570\u53ca\u5176\u8fd4\u56de\u503c\u7684\u7c7b\u578b\u3002<br \/>\n<strong>3.3.1 Types<\/strong><br \/>\n\u4f7f\u7528BCEL\u7684Type\u7c7b\u7528\u6cd5\u5982\u4e0b\uff1a<\/p>\n<pre class=\"brush: java; title: ; notranslate\" title=\"\">Type \u00a0 return_type = Type.VOID;\nType[] arg_types \u00a0 = new Type[] { new ArrayType(Type.STRING, 1) }\n<\/pre>\n<p><strong>3.3.2 Generic fields and methods<\/strong><br \/>\n\u57df\u9700\u8981\u4f7f\u7528FieldGen\u6765\u521b\u5efa\uff0c\u5e76\u4e14\u9700\u8981\u6307\u5b9a\u5176\u8bbf\u95ee\u6743\u9650\u3002\u65b9\u6cd5\u5219\u9700\u8981\u6dfb\u52a0\u53ef\u80fd\u9700\u8981\u7684\u5f02\u5e38\u3001local variables\u3001exception handler\u3002\u7531\u4e8e\u5305\u542b\u6709byte code\u7684\u5730\u5740\u7684\u5f15\u7528\uff0c\u8fd9\u4e24\u8005\u88ab\u79f0\u4e4b\u4e3ainstruction targeter\uff0c\u8fd9\u4e9btargeter\u5305\u542b\u6709updateTarget()\u65b9\u6cd5\uff0c\u7528\u4e8e\u66f4\u65b0\u76ee\u6807\u5730\u5740\uff0c\u8fd9\u4e2a\u5730\u65b9\u662f\u91c7\u7528Observer\u6a21\u5f0f\u5b9e\u73b0\u7684\u3002\u4e00\u822c\u65b9\u6cd5\uff08\u4e0d\u662f\u62bd\u8c61\u65b9\u6cd5\uff09\u4f1a\u6307\u5411\u4e00\u4e2ainstruction list\uff08\u5305\u542binstruction\u5bf9\u8c61\uff09\uff0c\u5bf9byte code\u5730\u5740\u7684\u5f15\u7528\u7531instruction\u5bf9\u8c61\u5904\u7406\uff0c\u5f53instruction list\u66f4\u65b0\u65f6\uff0cinstruction targeter\u4e5f\u4f1a\u88ab\u66f4\u65b0\u3002<br \/>\n\u6bcf\u4e2a\u65b9\u6cd5\u7684maximum stack size\u548cmaximum number of local variables\u53ef\u4ee5\u624b\u52a8\u6216\u662f\u91c7\u7528setMaxStack()\u548csetMaxLocals()\u65b9\u6cd5\u81ea\u52a8\u8bbe\u7f6e\u3002<br \/>\n<strong>3.3.3 Instructions<\/strong><br \/>\ninstruction\u5305\u542b\u6709 opcode(\u6709\u65f6\u53eb\u505atag)\uff0c\u5b57\u8282\u957f\u5ea6\uff0c\u5728byte code\u4e2d\u7684\u504f\u79fb\u91cf\u3002\u6709\u4e9b\u6307\u4ee4\u662f\u4e0d\u53ef\u53d8\u7684\uff08\u6bd4\u5982operators\uff09\uff0cInstructionConstants\u7528\u4e8e\u63d0\u4f9b\u9884\u5b9a\u4e49\u7684\u5e38\u91cf\u4f9b\u7528\u6237\u4f7f\u7528\uff08flyweight\u6a21\u5f0f\uff09\u3002<br \/>\n\u6307\u4ee4\u5206\u7c7b\uff1a\u6309\u7167type hierarchy of instruction classes\uff08\u9644\u5f55\u6709\uff09\u3002\u4e5f\u53ef\u4ee5\u6309\u7167\u6240\u5b9e\u73b0\u7684\u63a5\u53e3\u5206\u7c7b\u3002<br \/>\n\u91cd\u8981\u7684\u6307\u4ee4\uff1abranch instructions\uff0c\u6bd4\u5982goto\uff0c\u4f7f\u5f97\u8fd9\u4e9b\u6307\u4ee4\u4e5f\u53ef\u4ee5\u770b\u505ainstruction targeter\u3002<br \/>\n\u6240\u6709\u6307\u4ee4\u90fd\u53ef\u4ee5\u901a\u8fc7accept(Visitor v)\u65b9\u6cd5\u6765\u8bbf\u95ee\uff08visitor\u6a21\u5f0f\uff09\u3002\uff083.3.3 Instructions\uff09<br \/>\n<strong>3.3.4 Instruction lists<\/strong><br \/>\ninstruction list\uff1a\u5bf9instructions\u7684\u5f15\u7528\u4e0d\u662f\u7531\u76f4\u63a5\u6307\u5411instruction\u7684\u6307\u9488\uff0c\u800c\u662f\u6307\u5411instruction handle\u7684\u6307\u9488\u3002\u8fd9\u4f7f\u5f97\u6dfb\u52a0\u3001\u63d2\u5165\u3001\u5220\u9664byte code\u5f88\u65b9\u4fbf\uff0c\u540c\u65f6\u5141\u8bb8\u91cd\u7528\u4e0d\u53ef\u53d8\u7684\u6307\u4ee4\u5bf9\u8c61\uff08flyweight object\uff09\u3002\u7531\u4e8e\u4f7f\u7528\u7b26\u53f7\u5f15\u7528\uff0c\u5177\u4f53\u7684bytecode\u504f\u79fb\u91cf\u7684\u8ba1\u7b97\u76f4\u5230finalization\u624d\u8ba1\u7b97\u5373\u53ef\uff0c\u5373\u7528\u6237\u505c\u6b62\u64cd\u4f5cbytecode\u7684\u65f6\u5019\u3002\u4e0b\u6587\u5c06instruction handle\u548cinstruction\u89c6\u4e3a\u540c\u4e00\u6982\u5ff5\u3002instruction handle\u901a\u8fc7addAttribute()\u65b9\u6cd5\u53ef\u4ee5\u5305\u542b\u6709\u7528\u6237\u81ea\u5b9a\u4e49\u6570\u636e\u3002<br \/>\n<strong>append\u64cd\u4f5c<\/strong>\uff1a<br \/>\ninstructionlist\u7684append\u65b9\u6cd5\u4f1a\u8fd4\u56de\u4e00\u4e2ainstruction handle\uff0c\u7528\u4f5cbranch instruction\u7684\u76ee\u6807\u5730\u5740\u3002<\/p>\n<pre class=\"brush: java; title: ; notranslate\" title=\"\">InstructionList il = new InstructionList();\n...\nGOTO g = new GOTO(null);\nil.append(g);\n...\n\/\/ Use immutable fly-weight object\nInstructionHandle ih = il.append(InstructionConstants.ACONST_NULL);\ng.setTarget(ih);\n<\/pre>\n<p><strong>insert\u64cd\u4f5c<\/strong>\uff1a<br \/>\n\u6307\u4ee4\u53ef\u4ee5\u63d2\u5165\u5230\u73b0\u6709list\u7684\u4efb\u610f\u4f4d\u7f6e\uff0c\u9700\u8981\u63d2\u5165\u5230\u7ed9\u5b9ainstruction handle\u7684\u524d\u8fb9\uff0cinsert\u65b9\u6cd5\u4f1a\u8fd4\u56de\u4e00\u4e2ainstruction handle\u7528\u4e8e\u53ef\u80fd\u7684\u5f02\u5e38\u5904\u7406\u7684\u76ee\u6807\u5730\u5740\u3002<\/p>\n<pre class=\"brush: java; title: ; notranslate\" title=\"\">InstructionHandle start = il.insert(insertion_point,\nInstructionConstants.NOP);\n...\nmg.addExceptionHandler(start, end, handler, &amp;quot;java.io.IOException&amp;quot;);\n<\/pre>\n<p><strong>delete\u64cd\u4f5c<\/strong>\uff1a<br \/>\n\u9700\u8981\u7ed9\u51fa\u6307\u5b9a\u8303\u56f4\uff0c\u8be5\u8303\u56f4\u5185\u7684\u6307\u4ee4\u5c06\u88ab\u5220\u9664\u5e76\u91ca\u653e\u8d44\u6e90\uff08dispose\uff09\u3002\u4f46instruction targeter\u4ecd\u5f15\u7528\u7740\u5c06\u8981\u88ab\u5220\u9664\u7684\u6307\u4ee4\u65f6\uff0cdelete\u65b9\u6cd5\u53ef\u80fd\u629b\u51faTargetLostException\u3002\u7528\u6237\u9700\u8981\u81ea\u5df1\u5904\u7406\u8fd9\u4e9b\u5f02\u5e38\u3002\u53c2\u89c1\u9644\u5f55\u7684\u7aa5\u5b54\u4f18\u5316\u7684\u4f8b\u5b50\u3002<\/p>\n<pre class=\"brush: java; title: ; notranslate\" title=\"\">try {\nil.delete(first, last);\n} catch(TargetLostException e) {\nInstructionHandle[] targets = e.getTargets();\nfor(int i=0; i &amp;lt; targets.length; i++) {\nInstructionTargeter[] targeters = targets[i].getTargeters();\nfor(int j=0; j &amp;lt; targeters.length; j++)\ntargeters[j].updateTarget(targets[i], new_target);\n}\n};\n<\/pre>\n<p><strong>finalize\u64cd\u4f5c<\/strong>\uff1a<br \/>\n\u5f53instruction list\u5df2\u7ecf\u64cd\u4f5c\u5b8c\u6bd5\u3001\u6253\u7b97\u751f\u6210\u7eaf\u7cb9\u7684\u5b57\u8282\u7801\u65f6\uff0c\u6240\u6709\u7b26\u53f7\u5f15\u7528\u88ab\u6620\u5c04\u4e3a\u771f\u5b9e\u7684byte code offset\uff0c\u8fd9\u4e00\u64cd\u4f5c\u7531getByteCode()\u5b8c\u6210\uff08\u9ed8\u8ba4\u7531Method.getMethod()\uff09\u3002\u751f\u6210\u5b57\u8282\u7801\u540e\u7528\u6237\u5e94\u8be5\u8c03\u7528dispose()\u4e00\u904d\u4f7f\u5f97\u8fd9\u4e9binstrution handle\u80fd\u522b\u91cd\u7528\u3002<\/p>\n<pre class=\"brush: java; title: ; notranslate\" title=\"\">InstructionList il = new InstructionList();\nClassGen \u00a0cg = new ClassGen(\"HelloWorld\", \"java.lang.Object\",\n\"&lt;generated&gt;\", ACC_PUBLIC | ACC_SUPER,\nnull);\nMethodGen mg = new MethodGen(ACC_STATIC | ACC_PUBLIC,\nType.VOID, new Type[] {\nnew ArrayType(Type.STRING, 1)\n}, new String[] { \"argv\" },\n\"main\", \"HelloWorld\", il, cp);\n...\ncg.addMethod(mg.getMethod());\nil.dispose(); \/\/ Reuse instruction handles of list\n<\/pre>\n<p><strong>3.3.6 Instruction Factories<\/strong><br \/>\n\u4e3a\u4e86\u7b80\u5316\u67d0\u4e9b\u6307\u4ee4\u7684\u521b\u5efa\uff0c\u7528\u6237\u53ef\u4ee5\u4f7f\u7528InstructionFactory\u7c7b\u521b\u5efa\u6307\u4ee4\uff08\u63d0\u4f9b\u4e86\u5f88\u591a\u6709\u7528\u7684\u65b9\u6cd5\u7528\u4e8e\u521b\u5efa\u6307\u4ee4\uff09\uff0c\u4e5f\u53ef\u4ee5\u4f7f\u7528compound instruction\uff1a\u5f53\u4ea7\u751fbyte code\uff0c\u67d0\u4e9b\u201c\u6a21\u5f0f\u201d\u51fa\u73b0\u7684\u6bd4\u8f83\u9891\u7e41\uff0c\u6bd4\u5982\u7b97\u672f\u6216\u662f\u6bd4\u8f83\u8fd0\u7b97\uff0c\u53ef\u4ee5\u7528\u4e00\u4e2acompound instruction\uff08\u4e00\u4e2a\u53ea\u6709\u5355\u4e00\u7684\u4e00\u4e2agetInstructionList()\u65b9\u6cd5\u7684\u63a5\u53e3\uff09\uff0c\u8fd9\u53ef\u4ee5\u7528\u4e8e\u4efb\u4f55\u4f4d\u7f6e\uff0c\u5c24\u5176\u662f\u6dfb\u52a0\u64cd\u4f5c\u3002<br \/>\n\u4f8b\u5b50\uff1a\u5c06\u64cd\u4f5c\u6570\u538b\u5165\u6808\uff0c\u7528PUSH\u53ef\u4ee5\u81ea\u52a8\u4ea7\u751f\u5408\u9002\u7684\u6307\u4ee4<\/p>\n<pre class=\"brush: java; title: ; notranslate\" title=\"\">InstructionFactory f \u00a0= new InstructionFactory(class_gen);\nInstructionList \u00a0 \u00a0il = new InstructionList();\n...\nil.append(new PUSH(cp, \"Hello, world\"));\nil.append(new PUSH(cp, 4711));\n...\nil.append(f.createPrintln(\"Hello World\"));\n...\nil.append(f.createReturn(type));\n<\/pre>\n<p>regular expressions<br \/>\n\u53ef\u4ee5\u7528\u6b63\u5219\u8868\u8fbe\u5f0f\u6765\u641c\u7d22\u7279\u5b9a\u6a21\u5f0f\u7684\u4ee3\u7801\u3002\u2014\u2014org.apache.bcel.util.InstructionFinder\u7684search()\u65b9\u6cd5\uff0c\u627e\u5230\u540e\u4f1a\u8fd4\u56de\u4e00\u4e2a\u8fed\u4ee3\u5668\uff0c\u5176\u4ed6\u7684\u7ea6\u675f\u6761\u4ef6\u53ef\u4ee5\u901a\u8fc7code constraint\u5bf9\u8c61\u6765\u8868\u8fbe\u3002<\/p>\n<pre class=\"brush: java; title: ; notranslate\" title=\"\">CodeConstraint constraint = new CodeConstraint() {\npublic boolean checkCode(InstructionHandle[] match) {\nIfInstruction if1 = (IfInstruction)match[0].getInstruction();\nGOTO \u00a0 \u00a0 \u00a0 \u00a0 \u00a0g \u00a0 = (GOTO)match[2].getInstruction();\nreturn (if1.getTarget() == match[3]) &amp;&amp;\n(g.getTarget() == match[4]);\n}\n};\nInstructionFinder f \u00a0 \u00a0= new InstructionFinder(il);\nString \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0pat = \"IfInstruction ICONST_0 GOTO ICONST_1 NOP(IFEQ|IFNE)\";\nfor(Iterator e = f.search(pat, constraint); e.hasNext(); ) {\nInstructionHandle[] match = (InstructionHandle[])e.next();;\n...\nmatch[0].setTarget(match[5].getTarget()); \/\/ Update target\n...\ntry {\nil.delete(match[1], match[5]);\n} catch(TargetLostException ex) { ... }\n}\n<\/pre>\n<p>\u4f8b\u5b50\uff1a\u4f18\u5316boolean\u8868\u8fbe\u5f0f<\/p>\n<h2><strong>\u7528BCEL\u751f\u6210HelloWorld<\/strong><\/h2>\n<p>\u6700\u540e\uff0c\u4e3e\u4e2a\u7b80\u5355\u7684\u4f8b\u5b50\uff0c\u8bf4\u660e\u5177\u4f53\u5982\u4f55\u4f7f\u7528BCEL\u76f4\u63a5\u751f\u6210class\u6587\u4ef6\u3002\u6bd4\u5982\u8bf4\uff0c\u6211\u4eec\u73b0\u5728\u8981\u4f7f\u7528BCEL\u751f\u6210\u4e00\u4e2aHelloWorld.class\u6587\u4ef6\uff0c\u5b9e\u73b0\u5982\u4e0b\u4ee3\u7801\u7684\u529f\u80fd\uff1a<\/p>\n<pre class=\"brush: java; title: ; notranslate\" title=\"\">try {\n \/\/ BCEL Appendix A example\n \/\/ ClassGen(String class_name, String super_class_name, String\n \/\/ file_name, int access_flags, String[] interfaces)\n ClassGen cg = new ClassGen(\"HelloWorld\", \"java.lang.Object\",\n \"&lt;generated&gt;\", ACC_PUBLIC | ACC_SUPER, null);\n ConstantPoolGen cp = cg.getConstantPool();\n InstructionList il = new InstructionList();\n\/\/ create main method\n \/\/ MethodGen(int access_flags, Type return_type, Type[] arg_types,\n \/\/ String[] arg_names, String method_name, String class_name,\n \/\/ InstructionList il, ConstantPoolGen cp)\n MethodGen mg = new MethodGen(ACC_STATIC | ACC_PUBLIC, Type.VOID,\n new Type[] { new ArrayType(Type.STRING, 1) },\n new String[] { \"argv\" }, \"main\", \"HelloWorld\", il, cp);\nInstructionFactory factory = new InstructionFactory(cg);\n\/\/ define some often used types\n ObjectType i_stream = new ObjectType(\"java.io.InputStream\");\n ObjectType p_stream = new ObjectType(\"java.io.PrintStream\");\n \/\/%%\n \/\/BufferedReader in = new BufferedReader(new InputStreamReader(System.in));\n \/\/%%\n \/\/ create variables in and name\n il.append(factory.createNew(\"java.io.BufferedReader\"));\n il.append(InstructionConstants.DUP);\n il.append(factory.createNew(\"java.io.InputStreamReader\"));\n il.append(InstructionConstants.DUP);\n \/\/init input stream\n il.append(factory.createFieldAccess(\"java.lang.System\", \"in\",\n i_stream, Constants.GETSTATIC));\n il.append(factory.createInvoke(\"java.io.InputStreamReader\",\n \"&lt;init&gt;\", Type.VOID, new Type[] { i_stream },\n Constants.INVOKESPECIAL));\n il.append(factory.createInvoke(\"java.io.BufferedReader\", \"&lt;init&gt;\",\n Type.VOID, new Type[] { new ObjectType(\"java.io.Reader\") },\n Constants.INVOKESPECIAL));\n \/\/add in into the local variable pool and get the index automatically\n LocalVariableGen lg = mg.addLocalVariable(\"in\", new ObjectType(\n \"java.io.BufferedReader\"), null, null);\n int in = lg.getIndex();\/\/index of \"in\" var\n lg.setStart(il.append(new ASTORE(in)));\/\/store the reference into local variable\n \/\/\u9996\u5148\u521b\u5efa\u5bf9\u8c61\uff0c\u5e76\u521d\u59cb\u5316\uff0c\u64cd\u4f5c\u7ed3\u679c\u5728JVM\u7684\u201c\u5806\u201d\u91cc\uff0c\u8fd8\u9700\u8981\u5728\u672c\u5730\u53d8\u91cf\u8868\u4e2d\u521b\u5efa\u5f15\u7528\uff0c\u56e0\u6b64\u5728\u672c\u5730\u53d8\u91cf\u8868\u4e2d\u6dfb\u52a0\u4e00\u4e2a\u201cin\u201d\u6bd4\u90a3\u8f86\uff0c\n \/\/\u7136\u540e\u6839\u636e\u7d22\u5f15\u503c\u8c03\u7528\u201castore\u201d\u6307\u4ee4\uff0c\u5373\u53ef\u5c06\u5bf9\u8c61\u5f15\u7528\u8d4b\u503c\u7ed9\u672c\u5730\u53d8\u91cf\n \/*\n 0: new #8; \/\/class java\/io\/BufferedReader\n 3: dup\n 4: new #10; \/\/class java\/io\/InputStreamReader\n 7: dup\n 8: getstatic #16; \/\/Field java\/lang\/System.in:Ljava\/io\/InputStream;\n 11: invokespecial #20; \/\/Method java\/io\/InputStreamReader.\"&lt;init&gt;\":(Ljava\/io\/InputStream;)V\n 14: invokespecial #23; \/\/Method java\/io\/BufferedReader.\"&lt;init&gt;\":(Ljava\/io\/Reader;)V\n 17: astore_1\n * *\/\n\/\/%%\n \/\/String name = null;\n \/\/%%\n \/\/ create local variable name and init it to null\n lg = mg.addLocalVariable(\"name\", Type.STRING, null, null);\n int name = lg.getIndex();\n il.append(InstructionConstants.ACONST_NULL);\/\/add \"null\" to the stack top\n lg.setStart(il.append(new ASTORE(name)));\/\/\"store\" the value of \"null\" into \"name\" var\n\/\/%%\n \/\/System.out.print(\"Please enter your name&gt; \")\n \/\/%%\n \/\/ create try_catch block\n InstructionHandle try_start = il.append(factory.createFieldAccess(\n \"java.lang.System\", \"out\", p_stream, Constants.GETSTATIC));\n \/\/\u4ece\u5e38\u91cf\u6c60\u4e2d\u53d6\u51fa\u201cplease .....\u201d\uff0c\u538b\u5165\u6808\u9876\uff1a\u8fd9\u91cc\u611f\u89c9\u6709\u95ee\u9898\uff0c\u8fd9\u4e2a\u5b57\u7b26\u4e32\u5e38\u91cf\u5e94\u8be5\u5148\u538b\u5165\u5e38\u91cf\u6c60\u624d\u53ef\u4ee5\uff08\u6700\u597d\u662f\u5728\u8fd9\u4e4b\u524d\u52a0\u4e00\u53e5\uff0c\n \/\/\u52a0\u4e00\u53e5\u6dfb\u52a0\u5e38\u91cf\u6c60\u64cd\u4f5c\u5176\u5b9e\u5e76\u4e0d\u5f71\u54cd\u5b9e\u9645\u8fd0\u884c\u7684\u6548\u7387\uff09\n il.append(new PUSH(cp, \"Please enter your name&gt; \"));\n il.append(factory.createInvoke(\"java.io.PrintStream\", \"print\",\n Type.VOID, new Type[] { Type.STRING },\n Constants.INVOKEVIRTUAL));\n \/\/%%\n \/\/name = in.readLine();\n \/\/%%\n \/\/\u5c06\u672c\u5730\u53d8\u91cf\u201cin\u201d\u63a8\u9001\u81f3\u6808\u9876\n il.append(new ALOAD(in));\n il.append(factory.createInvoke(\"java.io.BufferedReader\",\n \"readLine\", Type.STRING, Type.NO_ARGS,\n Constants.INVOKEVIRTUAL));\/\/\u8c03\u7528readLine()\u65b9\u6cd5\n il.append(new ASTORE(name));\/\/\u63a5\u6536\u7684\u7ed3\u679c\u5728\u6808\u9876\uff0c\u9700\u8981\u4fdd\u5b58\uff0c\u56e0\u6b64\u52a0\u4e0a\u4fdd\u5b58\u5230\u201cname\u201dslot\u7684\u6307\u4ee4\n\/\/%%\n \/\/ } catch(IOException e) { return; }\n \/\/%%\n GOTO g = new GOTO(null);\n InstructionHandle try_end = il.append(g);\n \/\/add return\uff1a\u5982\u679c\u51fa\u5f02\u5e38\uff0c\u624d\u4f1a\u8d70\u5230\u8fd9\u6761\u201creturn\u201d\u6307\u4ee4\uff0c\u5e76\u8fd4\u56de\u5230caller\u4e2d\n InstructionHandle handler = il.append(InstructionConstants.RETURN);\n \/\/ add exception handler which returns from the method\n mg.addExceptionHandler(try_start, try_end, handler, null);\n\/\/%%\n \/\/\u6ca1\u6709\u5f02\u5e38\uff0c\u7ee7\u7eed\u6267\u884c\uff1aSystem.out.println(\"Hello, \" + name);\n \/\/%%\n \/\/ \"normal\" code continues, set the branch target of the GOTO\n InstructionHandle ih = il.append(factory.createFieldAccess(\n \"java.lang.System\", \"out\", p_stream, Constants.GETSTATIC));\n g.setTarget(ih);\n\/\/ print \"Hello\"\uff1a\u521b\u5efa\u4e00\u4e2aStringBuffer\u5bf9\u8c61\uff0c\u901a\u8fc7\u8c03\u7528StringBuffer\u7684append\u64cd\u4f5c\uff0c\u5b9e\u73b0\n \/\/string1 + string2\u7684\u64cd\u4f5c\uff0c\u5e76\u4e14\u64cd\u4f5c\u7ed3\u679c\u8c03\u7528toString\u65b9\u6cd5\n il.append(factory.createNew(Type.STRINGBUFFER));\n il.append(InstructionConstants.DUP);\n il.append(new PUSH(cp, \"Hello, \"));\n il.append(factory.createInvoke(\"java.lang.StringBuffer\", \"&lt;init&gt;\",\n Type.VOID, new Type[] { Type.STRING },\n Constants.INVOKESPECIAL));\n il.append(new ALOAD(name));\n il.append(factory.createInvoke(\"java.lang.StringBuffer\", \"append\",\n Type.STRINGBUFFER, new Type[] { Type.STRING },\n Constants.INVOKEVIRTUAL));\n \/\/\n il.append(factory.createInvoke(\"java.lang.StringBuffer\",\n \"toString\", Type.STRING, Type.NO_ARGS,\n Constants.INVOKEVIRTUAL));\n il.append(factory.createInvoke(\"java.io.PrintStream\", \"println\",\n Type.VOID, new Type[] { Type.STRING },\n Constants.INVOKEVIRTUAL));\n il.append(InstructionConstants.RETURN);\n\/\/ finalization\n mg.setMaxStack();\n cg.addMethod(mg.getMethod());\n il.dispose();\n cg.addEmptyConstructor(ACC_PUBLIC);\n\/\/ dump the class\ncg.getJavaClass().dump(\"HelloWorld.class\");\n System.out.println(\"dump successly\");\n } catch (java.io.IOException e) {\n System.err.println(e);\n } catch (Exception e1) {\n e1.printStackTrace();\n }\n<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>\u6ce8\u610f\uff1a\u672c\u6587\u7ae0\u4e3b\u8981\u4f9d\u636eBCEL\u5b98\u65b9\u624b\u518c\u8fdb\u884c\u9610\u8ff0\uff0c\u5927\u90e8\u5206\u5185\u5bb9\u90fd\u662f\u4ece\u8be5\u624b\u518c\u76f4\u63a5\u7ffb\u8bd1\u8fc7\u6765\u7684\uff0c\u5e76\u505a\u4e86\u4e00\u5b9a\u7684\u7b80\u5316\uff0c\u540c\u65f6\u8fd8\u53c2 <a href='http:\/\/prayerlaputa.com\/?p=76' class='excerpt-more'>[&#8230;]<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0},"categories":[6,12,22],"tags":[33,44,54],"_links":{"self":[{"href":"http:\/\/prayerlaputa.com\/index.php?rest_route=\/wp\/v2\/posts\/76"}],"collection":[{"href":"http:\/\/prayerlaputa.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/prayerlaputa.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/prayerlaputa.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/prayerlaputa.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=76"}],"version-history":[{"count":0,"href":"http:\/\/prayerlaputa.com\/index.php?rest_route=\/wp\/v2\/posts\/76\/revisions"}],"wp:attachment":[{"href":"http:\/\/prayerlaputa.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=76"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/prayerlaputa.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=76"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/prayerlaputa.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=76"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}