十 使用JDK中的Proxy技术实现AOP功能

十 使用JDK中的Proxy技术实现AOP功能

通过代理对象来调用对象的方法，从而做出权限控制。

目标对象必须实现接口才能使用proxy技术创建代理对象。

PersonService.java

view plaincopy to clipboardprint?
01.package cn.pf.aop.service;   
02.  
03.public interface PersonService {   
04.    public void save(String name);   
05.    public void update(String name, Integer personId);   
06.    public String getName(Integer personId);   
07.}  
package cn.pf.aop.service;

public interface PersonService {
	public void save(String name);
	public void update(String name, Integer personId);
	public String getName(Integer personId);
}
 

PersonServiceBean.java

view plaincopy to clipboardprint?
01.package cn.pf.aop.service.impl;   
02.  
03.import cn.pf.aop.service.PersonService;   
04.  
05.public class PersonServiceBean implements PersonService {   
06.    private String user = null;   
07.       
08.    public PersonServiceBean() {   
09.  
10.    }   
11.  
12.    public PersonServiceBean(String user) {   
13.        this.setUser(user);   
14.    }   
15.  
16.    @Override  
17.    public String getName(Integer personId) {   
18.        System.out.println(this.getClass().getName()+" getName方法");   
19.        return "pf";   
20.    }   
21.  
22.    @Override  
23.    public void save(String name) {   
24.        System.out.println(this.getClass().getName()+" save方法");   
25.    }   
26.  
27.    @Override  
28.    public void update(String name, Integer personId) {   
29.        System.out.println(this.getClass().getName()+" update方法");   
30.    }   
31.  
32.    public void setUser(String user) {   
33.        this.user = user;   
34.    }   
35.  
36.    public String getUser() {   
37.        return user;   
38.    }   
39.  
40.}  
package cn.pf.aop.service.impl;

import cn.pf.aop.service.PersonService;

public class PersonServiceBean implements PersonService {
	private String user = null;
	
	public PersonServiceBean() {

	}

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

	@Override
	public String getName(Integer personId) {
		System.out.println(this.getClass().getName()+" getName方法");
		return "pf";
	}

	@Override
	public void save(String name) {
		System.out.println(this.getClass().getName()+" save方法");
	}

	@Override
	public void update(String name, Integer personId) {
		System.out.println(this.getClass().getName()+" update方法");
	}

	public void setUser(String user) {
		this.user = user;
	}

	public String getUser() {
		return user;
	}

}
 

JDKProxyFactory.java

view plaincopy to clipboardprint?
01.package cn.pf.aop;   
02.  
03.import java.lang.reflect.InvocationHandler;   
04.import java.lang.reflect.Method;   
05.import java.lang.reflect.Proxy;   
06.  
07.import cn.pf.aop.service.impl.PersonServiceBean;   
08.  
09.public class JDKProxyFactory implements InvocationHandler {   
10.    private Object targetObject;   
11.       
12.    public Object createProxyIntance(Object targetObject){   
13.        this.targetObject = targetObject;   
14.        return Proxy.newProxyInstance(this.targetObject.getClass().getClassLoader(),    
15.                this.targetObject.getClass().getInterfaces(), this);   
16.    }   
17.  
18.    @Override  
19.    public Object invoke(Object proxy, Method method, Object[] arg2)   
20.            throws Throwable {   
21.        PersonServiceBean personServiceBean = (PersonServiceBean)targetObject;   
22.        Object result = null;   
23.        if(personServiceBean.getUser() != null){   
24.            result = method.invoke(targetObject, arg2);   
25.        }   
26.        return null;   
27.    }   
28.}  
package cn.pf.aop;

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

import cn.pf.aop.service.impl.PersonServiceBean;

public class JDKProxyFactory implements InvocationHandler {
	private Object targetObject;
	
	public Object createProxyIntance(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[] arg2)
			throws Throwable {
		PersonServiceBean personServiceBean = (PersonServiceBean)targetObject;
		Object result = null;
		if(personServiceBean.getUser() != null){
			result = method.invoke(targetObject, arg2);
		}
		return null;
	}
}
 

AOPTest.java

view plaincopy to clipboardprint?
01.package junit.test;   
02.  
03.import org.junit.Test;   
04.  
05.import cn.pf.aop.JDKProxyFactory;   
06.import cn.pf.aop.service.PersonService;   
07.import cn.pf.aop.service.impl.PersonServiceBean;   
08.  
09.  
10.public class AOPTest {   
11.    @Test public void proxyTest(){   
12.        JDKProxyFactory factory = new JDKProxyFactory();   
13.        PersonService personService = (PersonService) factory.createProxyIntance(new PersonServiceBean());   
14.        personService.save("111");   
15.    }   
16.}  
package junit.test;

import org.junit.Test;

import cn.pf.aop.JDKProxyFactory;
import cn.pf.aop.service.PersonService;
import cn.pf.aop.service.impl.PersonServiceBean;


public class AOPTest {
	@Test public void proxyTest(){
		JDKProxyFactory factory = new JDKProxyFactory();
		PersonService personService = (PersonService) factory.createProxyIntance(new PersonServiceBean());
		personService.save("111");
	}
}
 

Proxy.newProxyInstance(this.targetObject.getClass().getClassLoader(), this.targetObject.getClass().getInterfaces(), this);

创建代理对象的时候，加入了该目标对象所有的接口，即对所有的方法进行监听，任何一个方法的调用都会触发代理对象的invoke方法。this表示触发哪个代理对象的invoke方法，这里我们设置当前代理对象。

调用personService的save方法的时候，可以理解为，save方法被监听，进入代理对象的invoke方法，如果user！=null，则invoke方法中调用了personService的save方法，如果user==null，则什么也不做。

通过反射技术调用方法其实可以简单的理解为

xxx.invoke(obj,args)返回的结果是obj.xxx(args) 

end 完毕！