java动态代理工厂类

package com.czp.util;


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


/**
 * 代理生成工厂,要求其子类实现before(...),after(...),onException(...) 实现处理业务
 * 
 * @author caozhongping
 * 
 */
public abstract class ProxyFacty<T> implements InvocationHandler {


    private T target;
    public ProxyFacty(T target) {
        super();
        this.target = target;
    }


    /**
     * 创建代理，如果目标类没有实现接口则返回自己
     * 
     * @param target
     * @return
     */
    @SuppressWarnings("unchecked")
    public T getProxy() {
        Class<T> cls = (Class<T>) target.getClass();
        if (cls.getInterfaces() != null) {
            return (T) Proxy.newProxyInstance(cls.getClassLoader(),
                    cls.getInterfaces(), this);
        }
        return target;
    }


    /***
     * 通过代理实现调用
     */
    @Override
    public Object invoke(Object proxy, Method method, Object[] args)
            throws Throwable {
        Object obj = null;
        try 
        {
            before(args);
            obj = method.invoke(target, args);
            after(args);
        } catch (Exception e) {
            onException(e);
        }
        return obj;
    }


    /***
     * 出现异常时处理
     * 
     * @param ex
     */
    public abstract void onException(Exception ex);


    /**
     * 调用方法后处理
     * 
     * @param args
     */
    public abstract void after(Object[] args);


    /**
     * 调用方法前处理
     * 
     * @param args
     */
    public abstract void before(Object[] args);
}
//目标对象的接口

package com.czp.util;

public interface TestItf {

    void say(String name)throws Exception;
}
//目标对象

package com.czp.util;

public class TestItfImpl implements TestItf {

    @Override
    public void say(String name) throws Exception {
        if(name==null)
            throw new Exception("name is null");
        System.out.println("Hell, "+name);

    }

}
//代理工具类，继承工厂类实现拦截
package com.czp.util;


public class ProxyUtil<T> extends ProxyFacty<T>{

    

    public ProxyUtil(T target) {
        super(target);
    }

    @Override
    public void onException(Exception ex) {
        System.out.println("call Method error:"+ex);
        
    }

    @Override
    public void after(Object[] args) {
        System.out.println("----------exit method-----------");
        
    }

    @Override
    public void before(Object[] args) {
        System.out.println("-----Enter method------");
        
    }
    public static void main(String[] args) throws Exception {
        TestItf target = new TestItfImpl();//目标对象
        TestItf proxy = new ProxyUtil<TestItf>(target).getProxy();//目标的代理实例
        proxy.say("WengJiaBao");//正常调用
        //异常调用
        proxy.say(null);
    }
}
//输出：
-----Enter method------
Hell, WengJiaBao
----------exit method-----------
-----Enter method------
call Method error:java.lang.reflect.InvocationTargetException