public Object invoke(Object proxy, Method method, Object[] args) throws Throwable 
  {
 method.invoke(obj, args);
 return null;
}

A method invocation on a proxy instance through one of its proxy interfaces will be dispatched to the invoke method of the instance's invocation handler, passing the proxy instance,a java.lang.reflect.Method object identifying the method that was invoked, and an array of type Object containing the arguments. 

//抽象角色（动态代理只能代理接口） 
public interface Subject { 
   
  public void request(); 
} 

//真实角色：实现了Subject的request()方法 
public class RealSubject implements Subject{ 
   
  public void request(){ 
    System.out.println("From real subject."); 
  } 
} 

//实现了InvocationHandler 
public class DynamicSubject implements InvocationHandler 
{ 
  private Object obj;//这是动态代理的好处，被封装的对象是Object类型，接受任意类型的对象 
 
  public DynamicSubject() 
  { 
  } 
 
  public DynamicSubject(Object obj) 
  { 
    this.obj = obj; 
  } 
 
  //这个方法不是我们显示的去调用 
  public Object invoke(Object proxy, Method method, Object[] args) throws Throwable 
  { 
    System.out.println("before calling " + method); 
 
    method.invoke(obj, args); 
 
    System.out.println("after calling " + method); 
 
    return null; 
  } 
 
} 

//客户端：生成代理实例，并调用了request()方法 
public class Client { 
 
  public static void main(String[] args) throws Throwable{ 
    // TODO Auto-generated method stub 
 
    Subject rs=new RealSubject();//这里指定被代理类 
    InvocationHandler ds=new DynamicSubject(rs); 
    Class<?> cls=rs.getClass(); 
     
    //以下是一次性生成代理 
     
    Subject subject=(Subject) Proxy.newProxyInstance( 
        cls.getClassLoader(),cls.getInterfaces(), ds); 
     
    //这里可以通过运行结果证明subject是Proxy的一个实例，这个实例实现了Subject接口 
    System.out.println(subject instanceof Proxy); 
     
    //这里可以看出subject的Class类是$Proxy0,这个$Proxy0类继承了Proxy，实现了Subject接口 
    System.out.println("subject的Class类是："+subject.getClass().toString()); 
     
    System.out.print("subject中的属性有："); 
     
    Field[] field=subject.getClass().getDeclaredFields(); 
    for(Field f:field){ 
      System.out.print(f.getName()+", "); 
    } 
     
    System.out.print("\n"+"subject中的方法有："); 
     
    Method[] method=subject.getClass().getDeclaredMethods(); 
     
    for(Method m:method){ 
      System.out.print(m.getName()+", "); 
    } 
     
    System.out.println("\n"+"subject的父类是："+subject.getClass().getSuperclass()); 
     
    System.out.print("\n"+"subject实现的接口是："); 
     
    Class<?>[] interfaces=subject.getClass().getInterfaces(); 
     
    for(Class<?> i:interfaces){ 
      System.out.print(i.getName()+", "); 
    } 
 
    System.out.println("\n\n"+"运行结果为："); 
    subject.request(); 
  } 
} 

public static Object newProxyInstance(ClassLoader loader, 
    Class<?>[] interfaces, 
    InvocationHandler h) 
throws IllegalArgumentException 
{ 
  if (h == null) { 
    throw new NullPointerException(); 
  } 
 
  /* 
   * Look up or generate the designated proxy class. 
   */ 
  Class cl = getProxyClass(loader, interfaces); 
 
  /* 
   * Invoke its constructor with the designated invocation handler. 
   */ 
  try { 
      /* 
      * Proxy源码开始有这样的定义： 
      * private final static Class[] constructorParams = { InvocationHandler.class }; 
      * cons即是形参为InvocationHandler类型的构造方法 
      */ 
    Constructor cons = cl.getConstructor(constructorParams); 
    return (Object) cons.newInstance(new Object[] { h }); 
  } catch (NoSuchMethodException e) { 
    throw new InternalError(e.toString()); 
  } catch (IllegalAccessException e) { 
    throw new InternalError(e.toString()); 
  } catch (InstantiationException e) { 
    throw new InternalError(e.toString()); 
  } catch (InvocationTargetException e) { 
    throw new InternalError(e.toString()); 
  } 
} 

class Proxy{ 
  InvocationHandler h=null; 
  protected Proxy(InvocationHandler h) { 
    this.h = h; 
  } 
  ... 
} 

public final class $Proxy0 extends Proxy implements Subject { 
  private static Method m1; 
  private static Method m0; 
  private static Method m3; 
  private static Method m2; 
 
  static { 
    try { 
      m1 = Class.forName("java.lang.Object").getMethod("equals", 
          new Class[] { Class.forName("java.lang.Object") }); 
 
      m0 = Class.forName("java.lang.Object").getMethod("hashCode", 
          new Class[0]); 
 
      m3 = Class.forName("***.RealSubject").getMethod("request", 
          new Class[0]); 
 
      m2 = Class.forName("java.lang.Object").getMethod("toString", 
          new Class[0]); 
 
    } catch (NoSuchMethodException nosuchmethodexception) { 
      throw new NoSuchMethodError(nosuchmethodexception.getMessage()); 
    } catch (ClassNotFoundException classnotfoundexception) { 
      throw new NoClassDefFoundError(classnotfoundexception.getMessage()); 
    } 
  } //static 
 
  public $Proxy0(InvocationHandler invocationhandler) { 
    super(invocationhandler); 
  } 
 
  @Override 
  public final boolean equals(Object obj) { 
    try { 
      return ((Boolean) super.h.invoke(this, m1, new Object[] { obj })) .booleanValue(); 
    } catch (Throwable throwable) { 
      throw new UndeclaredThrowableException(throwable); 
    } 
  } 
 
  @Override 
  public final int hashCode() { 
    try { 
      return ((Integer) super.h.invoke(this, m0, null)).intValue(); 
    } catch (Throwable throwable) { 
      throw new UndeclaredThrowableException(throwable); 
    } 
  } 
 
  public final void request() { 
    try { 
      super.h.invoke(this, m3, null); 
      return; 
    } catch (Error e) { 
    } catch (Throwable throwable) { 
      throw new UndeclaredThrowableException(throwable); 
    } 
  } 
 
  @Override 
  public final String toString() { 
    try { 
      return (String) super.h.invoke(this, m2, null); 
    } catch (Throwable throwable) { 
      throw new UndeclaredThrowableException(throwable); 
    } 
  } 
}