jad

反编译指定已加载类的源码

jad 命令将 JVM 中实际运行的 class 的 byte code 反编译成 java 代码，便于你理解业务逻辑；

  • 在 Arthas Console 上，反编译出来的源码是带语法高亮的，阅读更方便
  • 当然，反编译出来的 java 代码可能会存在语法错误，但不影响你进行阅读理解

参数说明

参数名称 参数说明
class-pattern 类名表达式匹配
[c:] 类所属 ClassLoader 的 hashcode
[E] 开启正则表达式匹配，默认为通配符匹配

使用参考

当有多个 ClassLoader 都加载了这个类时，jad 命令会输出对应 ClassLoader 实例的 hashcode，然后你只需要重新执行 jad 命令，并使用参数 -c <hashcode> 就可以反编译指定 ClassLoader 加载的那个类了；
  1. $ jad org.apache.log4j.Logger
  2.  
  3.  Found more than one class for: org.apache.log4j.Logger, Please use jad -c hashcode org.apache.log4j.Logger
  4.  HASHCODE  CLASSLOADER
  5.  69dcaba4  +-monitor's ModuleClassLoader
  6.  6e51ad67  +-java.net.URLClassLoader@6e51ad67
  7.              +-sun.misc.Launcher$AppClassLoader@6951a712
  8.                +-sun.misc.Launcher$ExtClassLoader@6fafc4c2
  9.  2bdd9114  +-pandora-qos-service's ModuleClassLoader
  10.  4c0df5f8  +-pandora-framework's ModuleClassLoader
  11.  
  12. Affect(row-cnt:0) cost in 38 ms.
  13. $ jad org.apache.log4j.Logger -c 69dcaba4
  14.  
  15. ClassLoader:
  16. +-monitor's ModuleClassLoader
  17.  
  18. Location:
  19. /Users/zhuyong/Downloads/taobao-hsf.sar/plugins/monitor/lib/log4j-1.2.14.jar
  20.  
  21. package org.apache.log4j;
  22.  
  23. import org.apache.log4j.spi.*;
  24.  
  25. public class Logger extends Category
  26. {
  27.     private static final String FQCN;
  28.  
  29.     protected Logger(String name)
  30.     {
  31.         super(name);
  32.     }
  33.  
  34.     public static Logger getLogger(String name)
  35.     {
  36.         return LogManager.getLogger(name);
  37.     }
  38.  
  39.     public static Logger getLogger(Class clazz)
  40.     {
  41.         return LogManager.getLogger(clazz.getName());
  42.     }
  43.  
  44.     public static Logger getRootLogger()
  45.     {
  46.         return LogManager.getRootLogger();
  47.     }
  48.  
  49.     public static Logger getLogger(String name, LoggerFactory factory)
  50.     {
  51.         return LogManager.getLogger(name, factory);
  52.     }
  53.  
  54.     public void trace(Object message)
  55.     {
  56.         if (repository.isDisabled(5000))
  57.         {
  58.             return;
  59.         }
  60.         if (Level.TRACE.isGreaterOrEqual(getEffectiveLevel()))
  61.         {
  62.             forcedLog(Logger.FQCN, Level.TRACE, message, null);
  63.         }
  64.     }
  65.  
  66.     public void trace(Object message, Throwable t)
  67.     {
  68.         if (repository.isDisabled(5000))
  69.         {
  70.             return;
  71.         }
  72.         if (Level.TRACE.isGreaterOrEqual(getEffectiveLevel()))
  73.         {
  74.             forcedLog(Logger.FQCN, Level.TRACE, message, t);
  75.         }
  76.     }
  77.  
  78.     public boolean isTraceEnabled()
  79.     {
  80.         if (repository.isDisabled(5000))
  81.         {
  82.             return false;
  83.         }
  84.         return Level.TRACE.isGreaterOrEqual(getEffectiveLevel());
  85.     }
  86.  
  87.     static
  88.     {
  89.         Logger.FQCN = Logger.class.getName();
  90.     }
  91.  
  92. }
  93.  
  94. Affect(row-cnt:1) cost in 190 ms.

反编译指定的方法：

  1. $ jad com.taobao.container.web.arthas.rest.MetricsController directMetrics
  2.  
  3. ClassLoader:
  4. +-com.taobao.pandora.boot.loader.ReLaunchURLClassLoader@1817d444
  5.   +-sun.misc.Launcher$AppClassLoader@14dad5dc
  6.     +-sun.misc.Launcher$ExtClassLoader@a38d7a3
  7.  
  8. Location:
  9. /Users/zhuyong/middleware/tomcat-web/tomcat-web-web/target/classes/
  10.  
  11. private Map<String, Object> directMetrics(String ip, String[] metrics) {
  12.     JSONObject obj;
  13.     HashMap<String, Object> result = new HashMap<String, Object>();
  14.     result.put("success", false);
  15.     String metricUrl = "http://" + ip + ":8006/metrics/specific";
  16.     String postBody = Arrays.stream(metrics).map(metric -> "metric=" + metric).collect(Collectors.joining("&"));
  17.     HttpClientUtils.Response resp = HttpClientUtils.sendPostRequest((String)metricUrl, (String)postBody);
  18.     if (resp.isSuccess() && (obj = JSON.parseObject(resp.getContent())).containsKey("success") && obj.getBoolean("success").booleanValue() && obj.containsKey("data")) {
  19.         JSONArray dataArray = obj.getJSONArray("data");
  20.         HashMap<String, Object> metricMap = new HashMap<String, Object>();
  21.         for (Object aDataArray : dataArray) {
  22.             JSONObject o = (JSONObject)aDataArray;
  23.             metricMap.put(o.getString("metric"), o.get("value"));
  24.         }
  25.         result.put("data", metricMap);
  26.         result.put("success", true);
  27.         return result;
  28.     }
  29.     return result;
  30. }
  31.  
  32. Affect(row-cnt:1) cost in 1508 ms.

原文: https://alibaba.github.io/arthas/jad.html