查看JDK动态代理生成的类的内容

首先我们先定义一个接口：

public interface PersonInter {    String test(String str);}

接着就是我们想的要生成的JDK代理类源码的代码：

public class JdkProxySourceClass {public static void writeClassToDisk(String path){byte[] classFile = ProxyGenerator.generateProxyClass("$proxy4", new Class[]{PersonInter.class});FileOutputStream fos = null;try {fos = new FileOutputStream(path);fos.write(classFile);fos.flush();} catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();}finally{if(fos != null){try {fos.close();} catch (IOException e) {e.printStackTrace();}}}}    @Test      public void testGenerateProxyClass() {      JdkProxySourceClass.writeClassToDisk("D:/$Proxy4.class");      }  }

重要的就是这一句话：byte[] classFile = ProxyGenerator.generateProxyClass("$proxy4", new Class[]{PersonInter.class});

OK接下来我们用反编译工具看一下生成的代理类源码：

import com.zkn.newlearn.gof.proxyhandler.PersonInter;import java.lang.reflect.InvocationHandler;import java.lang.reflect.Method;import java.lang.reflect.Proxy;import java.lang.reflect.UndeclaredThrowableException;public final class Proxy4 extends Proxy  implements PersonInter{  private static Method m1;  private static Method m2;  private static Method m3;  private static Method m0;  public Proxy4(InvocationHandler paramInvocationHandler)    throws   {    super(paramInvocationHandler);  }  public final boolean equals(Object paramObject)    throws   {    try    {      return ((Boolean)this.h.invoke(this, m1, new Object[] { paramObject })).booleanValue();    }    catch (RuntimeException localRuntimeException)    {      throw localRuntimeException;    }    catch (Throwable localThrowable)    {      throw new UndeclaredThrowableException(localThrowable);    }  }  public final String toString()    throws   {    try    {      return ((String)this.h.invoke(this, m2, null));    }    catch (RuntimeException localRuntimeException)    {      throw localRuntimeException;    }    catch (Throwable localThrowable)    {      throw new UndeclaredThrowableException(localThrowable);    }  }  public final String test(String paramString)    throws   {    try    {      return ((String)this.h.invoke(this, m3, new Object[] { paramString }));    }    catch (RuntimeException localRuntimeException)    {      throw localRuntimeException;    }    catch (Throwable localThrowable)    {      throw new UndeclaredThrowableException(localThrowable);    }  }  public final int hashCode()    throws   {    try    {      return ((Integer)this.h.invoke(this, m0, null)).intValue();    }    catch (RuntimeException localRuntimeException)    {      throw localRuntimeException;    }    catch (Throwable localThrowable)    {      throw new UndeclaredThrowableException(localThrowable);    }  }  static  {    try    {      m1 = Class.forName("java.lang.Object").getMethod("equals", new Class[] { Class.forName("java.lang.Object") });      m2 = Class.forName("java.lang.Object").getMethod("toString", new Class[0]);      m3 = Class.forName("com.zkn.newlearn.gof.proxyhandler.PersonInter").getMethod("test", new Class[] { Class.forName("java.lang.String") });      m0 = Class.forName("java.lang.Object").getMethod("hashCode", new Class[0]);      return;    }    catch (NoSuchMethodException localNoSuchMethodException)    {      throw new NoSuchMethodError(localNoSuchMethodException.getMessage());    }    catch (ClassNotFoundException localClassNotFoundException)    {      throw new NoClassDefFoundError(localClassNotFoundException.getMessage());    }  }}

从反编译出来的源码中我们可以看到在静态代码块中得到了equals、toString、hashCode和PersonInter接口中test方法的Method对象。当我们调用PersonInter中的test方法的时候：

  public final String test(String paramString)    throws   {    try    {      return ((String)this.h.invoke(this, m3, new Object[] { paramString }));    }    catch (RuntimeException localRuntimeException)    {      throw localRuntimeException;    }    catch (Throwable localThrowable)    {      throw new UndeclaredThrowableException(localThrowable);    }  }

其实是调用了InvocationHandler中的invoke方法，并传入了之前获取到的对应的Method和参数。在这里也简单的说一下为什么JDK的动态代理只能代理接口不能代理类，请注意看我们所得到的代理类的源码，注意看这一句：public final class Proxy4 extends Proxy implements PersonInter。生成的代理类默认继承了Proxy这个类，而java中又是单继承的，所以这里只能代理接口，不能代理类了。就像枚举类，不能继承别的枚举类一样。