java 动态代理

所谓Dynamic Proxy是这样一种class： 
      它是在运行时生成的class，在生成它时你必须提供一组interface给它，然后该class就宣称它实现了这些interface。你当然可以把该class的实例当作这些interface中的任何一个来用。当然啦，这个Dynamic Proxy其实就是一个Proxy，它不会替你作实质性的工作，在生成它的实例时你必须提供一个handler，由它接管实际的工作。

 

package com.laos.javassist;

 

public interface Service {
 
 public void serviceMethod(String parameter);
 
}

package com.laos.javassist;

public interface ServiceCallback {
 public void doCallback();
}

ServiceConsumer 类实现了Service接口和ServiceCallback接口

package com.laos.javassist;

public class ServiceConsumer implements ServiceCallback,Service {
 
 public void doCallback() {
  System.out.println("call back");
 }

 public void serviceMethod(String parameter) {
  System.out.println("service  "+parameter);
  doCallback();
 }

}

 

package com.laos.javassist;

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

public class InvocationObject implements InvocationHandler {
 /**
  * 目标对象
  */
 private Object obj;
 public InvocationObject(Object target){
  this.obj = target;
 }
 public Object invoke(Object proxy, Method method, Object[] args)
   throws Throwable {
  //目标对象的方法，也即是目标对象实现接口的方法
  return method.invoke(obj, args);
 }
}

 

package com.laos.javassist;

import java.lang.reflect.Proxy;
/**
 * 动态代理
 * @author shuzt
 *
 */
public class ProxyFactoryUtils {
 /**
  * 生成代理对象
  * @param interfaceClass
  * @param targetClass
  * @return
  * @throws IllegalArgumentException
  * @throws InstantiationException
  * @throws IllegalAccessException
  */
 public static Object getProxyInstance(Class[] interfaceClasses,Object targetClass)
   throws IllegalArgumentException, InstantiationException,
   IllegalAccessException {
  //调用代理Proxy实例化一个目标对象的实例
  return Proxy.newProxyInstance(interfaceClasses[0].getClassLoader(),
    interfaceClasses, new InvocationObject(targetClass));
 }
 
 public static void main(String[] args){
  ServiceConsumer consumer = new ServiceConsumer();
  try {
   Object proxy = ProxyFactoryUtils.getProxyInstance(new Class[]{Service.class,ServiceCallback.class}, consumer);
   Service service = (Service)proxy;
   ServiceCallback serviceBack = (ServiceCallback)proxy;
   
   service.serviceMethod("hello");
   serviceBack.doCallback();
  } catch (IllegalArgumentException e) {
   
  } catch (InstantiationException e) {
   
  } catch (IllegalAccessException e) {
   
  }
 }
}

注意：如果ServiceConsumer 没有实现接口，调用不会出现异常！