Aop是面向切面的编程，我的理解就是给他套包装，一层套一层。

首先来看看如何返回一个对象的代理。

package agint;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
/**
 * 打印日志
 * @author Administrator
 *
 */
public class ShowLogHanlder implements InvocationHandler{
	/**
	 * 目标对象
	 */
	private Object target;
	/**
	 * 代理初始化
	 * @param target
	 * @return
	 */
	public static Object initNextAngient( Object target){
		 return Proxy.newProxyInstance(target.getClass().getClassLoader(),
				 target.getClass().getInterfaces(), 
				 new ShowLogHanlder(target));
	}

	public ShowLogHanlder(Object target) {
		super();
		this.target = target;
	}
	/**
	 * 自己的代理逻辑实现
	 */
	@Override
	public Object invoke(Object proxy, Method method, Object[] args)
			throws Throwable {
		System.out.println("计算开始");
		Object obj=method.invoke(target, args);
		System.out.println("计算结束");
		return obj;
	}

}

如何实现多个代理对象的嵌套呢

package agint;

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

public class ChackValueHanlder implements  InvocationHandler{
	
	private Object target;
	
	public static Object initNextAngient( Object target){
		 return Proxy.newProxyInstance(target.getClass().getClassLoader(),
				 target.getClass().getInterfaces(), 
				 new ChackValueHanlder(target));
	}
	
	public ChackValueHanlder(Object target){
		this.target=target;
	}

	
	public void CheakValue(Object obj){
		double value=(Double) obj;
		if(value<0){
			System.out.println("数据必须大于0");
		}else{
			System.out.println("数据合法");
		}
	}


	@Override
	public Object invoke(Object proxy, Method method, Object[] args)
			throws Throwable {
		for(Object obj:args){
			CheakValue(obj);
		}
		try {
			return method.invoke(target, args);
		} catch (Exception e) {
			e.printStackTrace();
		}
		return null;
	}

}

ShowLogHanlder.initNextAngient(ChackValueHanlder.initNextAngient(calucateImpl))