jdk和cglib代理过程详解

首先代理的目的都是一样的：就是不修改源代码的基础上，对以有的代码进行扩展。
jdk和cglib实现的手段是不一样的。

jdk代理是java本身类库包含的一种代理模式，不需要自己导入jar包。
下面程序的目的就是返回一个目标类对象target的一个代理对象，target是实现了一个接口的。

package com.mec;

import com.mec.IDoSomething;

public class Target implements IDoSomething {
    public Target() {
    }

    @Override
    public String doSomething(String str){
        System.out.println(str);
        return "["+str+"]";
    }

    public String test(){
        return "我是test方法";
    }
}

Proxy.newProxyInstance产生一个代理类对象。需要三个参数。

1. 目标类的类加载器来加载新的代理类（对ClassLoader还不是很了解）
2. 获取目标类实现的接口，对接口中存在的方法进行扩展。
3. 并且还需要传入一个InvocationHandler的实现类。
   InvocationHandler是一个接口，是用来控制代理方法具体执行过程的。当通过获取到的代理对象调用方法时，最后都会调用到invoke方法。invoke的三个参数分别是：
   1. proxy真实获取的代理对象，也就是Proxy.newProxyInstance会返回的代理对象。
   2. method是目标类中要被代理扩展的方法，也就是上面target的doSomething方法
   3. args就是method要的参数

public <T> T getJDKProxy(Object target) {
        Class<?> klass = target.getClass();
        ClassLoader classLoader = klass.getClassLoader();
        Class<?>[] interfaces = klass.getInterfaces();

        return (T) Proxy.newProxyInstance(classLoader, interfaces, new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                Object res = methodInvoker.invoke(target,method,args);
                return res;
            }
        });
    }

获取到的代理类不仅仅会对接口中的方法进行扩展，因为返回的对象是Object子类，所以对Object的一些方法也都会进行代理，比如toString（），hashcode（）等的。
下面我们把动态产生的代理类打印成class文件看一看。

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

被代理的方法有很多，不一一列举。只看我们接口中存在的方法dosomething（）；
h是Proxy类中的一个InvocationHandler成员变量，最后还是会调用到InvocationHandler的invoke方法，而这个invoke中就可以来写我们的具体代理过程，比如前置拦截和后置拦截等等。

cglib代理是需要外部导入jar包的。
cglib是产生的代理类是目标类的子类。
setCallback是设置方法的拦截器。

public <T> T getCglibProxy(Object target){
        Enhancer enhancer = new Enhancer();
        enhancer.setSuperclass(target.getClass());
        enhancer.setCallback(new MethodInterceptor(){
            @Override
            public Object intercept(Object obj, Method method, Object[] args, MethodProxy methodProxy) throws Throwable {
                Object res = methodInvoker.invoke(target,method,args);
                return res;
            }
        });

        return (T) enhancer.create();
    }

再看一下cglib产生的动态代理类是怎么样的。最后还是调用了Proxy内的h变量。
看了这俩个类，大概就是能理解其中执行的过程了。

import com.mec.Target..EnhancerByCGLIB..c7b51b3d;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.lang.reflect.UndeclaredThrowableException;
import net.sf.cglib.core.Signature;
import net.sf.cglib.proxy.Callback;
import net.sf.cglib.proxy.MethodProxy;

public final class $Proxy1 extends Proxy
  implements Target..EnhancerByCGLIB..c7b51b3d
{
  private static Method m1;
  private static Method m3;
  private static Method m6;
  private static Method m2;
  private static Method m8;
  private static Method m12;
  private static Method m18;
  private static Method m20;
  private static Method m0;
  private static Method m15;
  private static Method m11;
  private static Method m9;
  private static Method m7;
  private static Method m19;
  private static Method m10;
  private static Method m5;
  private static Method m17;
  private static Method m16;
  private static Method m13;
  private static Method m14;
  private static Method m4;

  public $Proxy1(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 (Error|RuntimeException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  public final Object newInstance(Callback[] paramArrayOfCallback)
    throws 
  {
    try
    {
      return (Object)this.h.invoke(this, m3, new Object[] { paramArrayOfCallback });
    }
    catch (Error|RuntimeException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  public final String test()
    throws 
  {
    try
    {
      return (String)this.h.invoke(this, m6, null);
    }
    catch (Error|RuntimeException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  public final String toString()
    throws 
  {
    try
    {
      return (String)this.h.invoke(this, m2, null);
    }
    catch (Error|RuntimeException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  public final String doSomething(String paramString)
    throws 
  {
    try
    {
      return (String)this.h.invoke(this, m8, new Object[] { paramString });
    }
    catch (Error|RuntimeException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  public final Callback getCallback(int paramInt)
    throws 
  {
    try
    {
      return (Callback)this.h.invoke(this, m12, new Object[] { Integer.valueOf(paramInt) });
    }
    catch (Error|RuntimeException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  public final Class getClass()
    throws 
  {
    try
    {
      return (Class)this.h.invoke(this, m18, null);
    }
    catch (Error|RuntimeException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  public final void notifyAll()
    throws 
  {
    try
    {
      this.h.invoke(this, m20, null);
      return;
    }
    catch (Error|RuntimeException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  public final int hashCode()
    throws 
  {
    try
    {
      return ((Integer)this.h.invoke(this, m0, null)).intValue();
    }
    catch (Error|RuntimeException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  public final void wait()
    throws InterruptedException
  {
    try
    {
      this.h.invoke(this, m15, null);
      return;
    }
    catch (Error|RuntimeException|InterruptedException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  public final void CGLIB$SET_STATIC_CALLBACKS(Callback[] paramArrayOfCallback)
    throws 
  {
    try
    {
      this.h.invoke(this, m11, new Object[] { paramArrayOfCallback });
      return;
    }
    catch (Error|RuntimeException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  public final void setCallbacks(Callback[] paramArrayOfCallback)
    throws 
  {
    try
    {
      this.h.invoke(this, m9, new Object[] { paramArrayOfCallback });
      return;
    }
    catch (Error|RuntimeException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  public final void setCallback(int paramInt, Callback paramCallback)
    throws 
  {
    try
    {
      this.h.invoke(this, m7, new Object[] { Integer.valueOf(paramInt), paramCallback });
      return;
    }
    catch (Error|RuntimeException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  public final void notify()
    throws 
  {
    try
    {
      this.h.invoke(this, m19, null);
      return;
    }
    catch (Error|RuntimeException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  public final void CGLIB$SET_THREAD_CALLBACKS(Callback[] paramArrayOfCallback)
    throws 
  {
    try
    {
      this.h.invoke(this, m10, new Object[] { paramArrayOfCallback });
      return;
    }
    catch (Error|RuntimeException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  public final Object newInstance(Class[] paramArrayOfClass, Object[] paramArrayOfObject, Callback[] paramArrayOfCallback)
    throws 
  {
    try
    {
      return (Object)this.h.invoke(this, m5, new Object[] { paramArrayOfClass, paramArrayOfObject, paramArrayOfCallback });
    }
    catch (Error|RuntimeException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  public final void wait(long paramLong)
    throws InterruptedException
  {
    try
    {
      this.h.invoke(this, m17, new Object[] { Long.valueOf(paramLong) });
      return;
    }
    catch (Error|RuntimeException|InterruptedException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  public final void wait(long paramLong, int paramInt)
    throws InterruptedException
  {
    try
    {
      this.h.invoke(this, m16, new Object[] { Long.valueOf(paramLong), Integer.valueOf(paramInt) });
      return;
    }
    catch (Error|RuntimeException|InterruptedException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  public final Callback[] getCallbacks()
    throws 
  {
    try
    {
      return (Callback[])this.h.invoke(this, m13, null);
    }
    catch (Error|RuntimeException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  public final MethodProxy CGLIB$findMethodProxy(Signature paramSignature)
    throws 
  {
    try
    {
      return (MethodProxy)this.h.invoke(this, m14, new Object[] { paramSignature });
    }
    catch (Error|RuntimeException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  public final Object newInstance(Callback paramCallback)
    throws 
  {
    try
    {
      return (Object)this.h.invoke(this, m4, new Object[] { paramCallback });
    }
    catch (Error|RuntimeException localError)
    {
      throw localError;
    }
    catch (Throwable localThrowable)
    {
      throw new UndeclaredThrowableException(localThrowable);
    }
  }

  static
  {
    try
    {
      m1 = Class.forName("java.lang.Object").getMethod("equals", new Class[] { Class.forName("java.lang.Object") });
      m3 = Class.forName("com.mec.Target$$EnhancerByCGLIB$$c7b51b3d").getMethod("newInstance", new Class[] { Class.forName("[Lnet.sf.cglib.proxy.Callback;") });
      m6 = Class.forName("com.mec.Target$$EnhancerByCGLIB$$c7b51b3d").getMethod("test", new Class[0]);
      m2 = Class.forName("java.lang.Object").getMethod("toString", new Class[0]);
      m8 = Class.forName("com.mec.Target$$EnhancerByCGLIB$$c7b51b3d").getMethod("doSomething", new Class[] { Class.forName("java.lang.String") });
      m12 = Class.forName("com.mec.Target$$EnhancerByCGLIB$$c7b51b3d").getMethod("getCallback", new Class[] { Integer.TYPE });
      m18 = Class.forName("com.mec.Target$$EnhancerByCGLIB$$c7b51b3d").getMethod("getClass", new Class[0]);
      m20 = Class.forName("com.mec.Target$$EnhancerByCGLIB$$c7b51b3d").getMethod("notifyAll", new Class[0]);
      m0 = Class.forName("java.lang.Object").getMethod("hashCode", new Class[0]);
      m15 = Class.forName("com.mec.Target$$EnhancerByCGLIB$$c7b51b3d").getMethod("wait", new Class[0]);
      m11 = Class.forName("com.mec.Target$$EnhancerByCGLIB$$c7b51b3d").getMethod("CGLIB$SET_STATIC_CALLBACKS", new Class[] { Class.forName("[Lnet.sf.cglib.proxy.Callback;") });
      m9 = Class.forName("com.mec.Target$$EnhancerByCGLIB$$c7b51b3d").getMethod("setCallbacks", new Class[] { Class.forName("[Lnet.sf.cglib.proxy.Callback;") });
      m7 = Class.forName("com.mec.Target$$EnhancerByCGLIB$$c7b51b3d").getMethod("setCallback", new Class[] { Integer.TYPE, Class.forName("net.sf.cglib.proxy.Callback") });
      m19 = Class.forName("com.mec.Target$$EnhancerByCGLIB$$c7b51b3d").getMethod("notify", new Class[0]);
      m10 = Class.forName("com.mec.Target$$EnhancerByCGLIB$$c7b51b3d").getMethod("CGLIB$SET_THREAD_CALLBACKS", new Class[] { Class.forName("[Lnet.sf.cglib.proxy.Callback;") });
      m5 = Class.forName("com.mec.Target$$EnhancerByCGLIB$$c7b51b3d").getMethod("newInstance", new Class[] { Class.forName("[Ljava.lang.Class;"), Class.forName("[Ljava.lang.Object;"), Class.forName("[Lnet.sf.cglib.proxy.Callback;") });
      m17 = Class.forName("com.mec.Target$$EnhancerByCGLIB$$c7b51b3d").getMethod("wait", new Class[] { Long.TYPE });
      m16 = Class.forName("com.mec.Target$$EnhancerByCGLIB$$c7b51b3d").getMethod("wait", new Class[] { Long.TYPE, Integer.TYPE });
      m13 = Class.forName("com.mec.Target$$EnhancerByCGLIB$$c7b51b3d").getMethod("getCallbacks", new Class[0]);
      m14 = Class.forName("com.mec.Target$$EnhancerByCGLIB$$c7b51b3d").getMethod("CGLIB$findMethodProxy", new Class[] { Class.forName("net.sf.cglib.core.Signature") });
      m4 = Class.forName("com.mec.Target$$EnhancerByCGLIB$$c7b51b3d").getMethod("newInstance", new Class[] { Class.forName("net.sf.cglib.proxy.Callback") });
      return;
    }
    catch (NoSuchMethodException localNoSuchMethodException)
    {
      throw new NoSuchMethodError(localNoSuchMethodException.getMessage());
    }
    catch (ClassNotFoundException localClassNotFoundException)
    {
      throw new NoClassDefFoundError(localClassNotFoundException.getMessage());
    }
  }
}

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