java动态代理分析

哈哈哈

Java代码 
二.源代码:   
  
被代理对象的接口及实现类:   
package com.ml.test;   
  
public interface Manager {   
public void modify();   
}   
  
package com.ml.test;   
  
public class ManagerImpl implements Manager {   
  
@Override  
public void modify() {   
   System.out.println("*******modify()方法被调用");   
}   
}   
  
业务代理类:   
package com.ml.test;   
  
import java.lang.reflect.InvocationHandler;   
import java.lang.reflect.Method;   
  
public class BusinessHandler implements InvocationHandler {   
  
private Object object = null;   
  
public BusinessHandler(Object object) {   
   this.object = object;   
}   
  
@Override  
public Object invoke(Object proxy, Method method, Object[] args)   
    throws Throwable {   
   System.out.println("do something before method");   
   Object ret = method.invoke(this.object, args);   
   System.out.println("do something after method");   
   return ret;   
  
}   
}   
  
  
  
客户端类:   
package com.ml.test;   
import java.lang.reflect.Proxy;   
public class Client {   
  
public static void main(String[] args) {   
   // 元对象(被代理对象)   
   ManagerImpl managerImpl = new ManagerImpl();   
  
   // 业务代理类   
   BusinessHandler securityHandler = new BusinessHandler(managerImpl);   
  
   // 获得代理类($Proxy0 extends Proxy implements Manager)的实例.   
   Manager managerProxy = (Manager) Proxy.newProxyInstance(managerImpl   
     .getClass().getClassLoader(), managerImpl.getClass()   
     .getInterfaces(), securityHandler);   
  
   managerProxy.modify();   
}   
}   
  
三.执行结果:   
do something before method   
*******modify()方法被调用   
do something after method   
  
四.机制分析:   
  
Proxy.(ClassLoader loader, Class<?>[] interfaces, InvocationHandler h)做了以下几件事.   
(1)根据参数loader和interfaces调用方法 getProxyClass(loader, interfaces)创建代理类$Proxy.   
$Proxy0类实现了interfaces的接口,并继承了Proxy类.   
(2)实例化$Proxy0并在构造方法中把BusinessHandler传过去,接着$Proxy0调用父类Proxy的构造器,为h赋值,如下:   
class Proxy{   
   InvocationHandler h=null;   
   protected Proxy(InvocationHandler h) {   
    this.h = h;   
   }   
   ...   
}   
  
  
  
下面是本例的$Proxy0类的源码(好不容易才把它提出来):   
  
  
import java.lang.reflect.InvocationHandler;   
import java.lang.reflect.Method;   
import java.lang.reflect.Proxy;   
import java.lang.reflect.UndeclaredThrowableException;   
  
public final class $Proxy0 extends Proxy implements Manager {   
  
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("com.ml.test.Manager").getMethod("modify",   
      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());   
   }   
}   
  
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 modify() {   
   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);   
   }   
}   
}   
  
接着把得到的$Proxy0实例强制转换成Manager.   
当执行managerProxy.modify()方法时,就调用了$Proxy0类中的modify()方法.   
在modify方法中,调用父类Proxy中的h的invoke()方法.   
即InvocationHandler.invoke();  

二.源代码:

被代理对象的接口及实现类:
package com.ml.test;

public interface Manager {
public void modify();
}

package com.ml.test;

public class ManagerImpl implements Manager {

@Override
public void modify() {
   System.out.println("*******modify()方法被调用");
}
}

业务代理类:
package com.ml.test;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;

public class BusinessHandler implements InvocationHandler {

private Object object = null;

public BusinessHandler(Object object) {
   this.object = object;
}

@Override
public Object invoke(Object proxy, Method method, Object[] args)
    throws Throwable {
   System.out.println("do something before method");
   Object ret = method.invoke(this.object, args);
   System.out.println("do something after method");
   return ret;

}
}



客户端类:
package com.ml.test;
import java.lang.reflect.Proxy;
public class Client {

public static void main(String[] args) {
   // 元对象(被代理对象)
   ManagerImpl managerImpl = new ManagerImpl();

   // 业务代理类
   BusinessHandler securityHandler = new BusinessHandler(managerImpl);

   // 获得代理类($Proxy0 extends Proxy implements Manager)的实例.
   Manager managerProxy = (Manager) Proxy.newProxyInstance(managerImpl
     .getClass().getClassLoader(), managerImpl.getClass()
     .getInterfaces(), securityHandler);

   managerProxy.modify();
}
}

三.执行结果:
do something before method
*******modify()方法被调用
do something after method

四.机制分析:

Proxy.(ClassLoader loader, Class<?>[] interfaces, InvocationHandler h)做了以下几件事.
(1)根据参数loader和interfaces调用方法 getProxyClass(loader, interfaces)创建代理类$Proxy.
$Proxy0类实现了interfaces的接口,并继承了Proxy类.
(2)实例化$Proxy0并在构造方法中把BusinessHandler传过去,接着$Proxy0调用父类Proxy的构造器,为h赋值,如下:
class Proxy{
   InvocationHandler h=null;
   protected Proxy(InvocationHandler h) {
    this.h = h;
   }
   ...
}



下面是本例的$Proxy0类的源码(好不容易才把它提出来):


import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.lang.reflect.UndeclaredThrowableException;

public final class $Proxy0 extends Proxy implements Manager {

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("com.ml.test.Manager").getMethod("modify",
      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());
   }
}

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 modify() {
   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);
   }
}
}

接着把得到的$Proxy0实例强制转换成Manager.
当执行managerProxy.modify()方法时,就调用了$Proxy0类中的modify()方法.
在modify方法中,调用父类Proxy中的h的invoke()方法.
即InvocationHandler.invoke();