编码实现用JDK中的Proxy实现springAOP功能

1、 创建一个被拦截对象接口peopleService
（横切性关注点）：

package com.wxy.service;
public interface PeopleService {
public void save(String name);

public void update(String name, Integer peopleId);

public String getPeopleName(Integer peopleId);

}

2、 实现被拦截对象接口

package com.wxy.service.impl;

import com.wxy.service.PeopleService;

public class PeopleServiceBean implements PeopleService {

private String user = null;

public PeopleServiceBean() {
}

public PeopleServiceBean(String user) {
this.setUser(user);
}

@Override
public String getPeopleName(Integer peopleId) {
System.out.println("我是getPeopleName()方法");
return "wxy";
}

@Override
public void save(String name) {
System.out.println("我是save()方法,save:" + name);
}

@Override
public void update(String name, Integer peopleId) {
System.out.println("我是update()方法");
}

/**
* @param user the user to set
*/
public void setUser(String user) {
this.user = user;
}

/**
* @return the user
*/
public String getUser() {
return user;
}

}

3、拦截所有的业务方法，

判断用户是否有权限，有权限就允许执行业务方法，没有权限则不允许执行业务方法（是否有权限是根据user是否为null为依据的）。

为目标对象创建动态代理类的类proxy（在jdk中的反射中）：

package com.wxy.aop;

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

import com.wxy.service.impl.PeopleServiceBean;

/**
*   创建代理工厂
*  当客户端调用代理对象的业务方法时，代理对象执行invoke方法，invoke方法把调用委派给targetObject
*  相当于调用目标对象的方法，在invoke方法委派前判断权限，实现方法的拦截
*   @creator            xiaoyu.wang
*   @create-time     2011-8-18   上午08:57:30
*   @revision          $Id
*/
public class JDKProxyFactory implements InvocationHandler {
private Object targetObject;

public Object createProxyInstance(Object targetObject) {
this.targetObject = targetObject;
return Proxy.newProxyInstance(this.targetObject.getClass().getClassLoader(),
this.targetObject.getClass().getInterfaces(), this);
}

@Override
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
PeopleServiceBean bean = (PeopleServiceBean) this.targetObject;//被代理对象
Object result = null;
if (bean.getUser() != null) {//有权限，user不为null
result = method.invoke(targetObject, args);
}
return result;
}

/**
* @param targetObject the targetObject to set
*/
public void setTargetObject(Object targetObject) {
this.targetObject = targetObject;
}

/**
* @return the targetObject
*/
public Object getTargetObject() {
return targetObject;
}

}

4、测试：

public class AOPTest {
public static void main(String[] args) {
JDKProxyFactory factory = new JDKProxyFactory();
PeopleService service = (PeopleService) factory.createProxyInstance(new PeopleServiceBean(
"wxy"));

service.save("wxy");
}

}

测试结果：

我是save()方法,save:wxy