实现AOP功能的封装与配置的小框架

Posted 2020-09-25

内容

java基础巩固笔记 - 实现AOP功能的封装与配置的小框架

设计（目录）：

XXX = java.util.ArrayList中

代码

Advice接口

MyAdvice类

BeanFactory类

ProxyFactoryBean类

AopFrameWorkTest类

输出

本文通过是动态代理实现的AOP功能的封装与配置的小框架.加深对动态代理和AOP编程的理解

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设计

根据配置文件的键xxx对应的值(类全名)创建相应类的对象。

当且仅当xxx对应的值为com.iot.proxy.aopframework.ProxyFactoryBean时，则生成相应的动态代理类对象。代理对象的目标类和通知实现类分别由xxx.target和xxx.advice配置

配置文件

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config.propertiest位于aopframework包下

xxx代表要加载的类

xxx.advice代表通知接口的某个实现类

xxx.target代表委托类

#xxx=java.util.ArrayList

xxx=com.iot.proxy.aopframework.ProxyFactoryBean

xxx.advice=com.iot.proxy.MyAdvice

xxx.target=java.util.ArrayList

包:com.iot.proxy.aopframework,有如下几个类/接口：

BeanFactory,用于读取配置文件，根据配置创建相应的对象

ProxyFactoryBean,用于生成代理对象，含有两个私有属性:目标和通知

Advice,通知接口，用于把切面的代码以对象的形式传递给InvocationHandler的的invoke方法

MyAdvice,Advice接口的一个实现类，打印执行方法前的时间及执行耗时

AopFrameWorkTest，测试效果

代码

Advice接口

package com.iot.proxy.aopframework;

import java.lang.reflect.Method;

/**

* Created by brian on 2016/2/2.

*/

public interface Advice {

void beforeMethod(Method method);

void aftereMethod(Method method);

}

MyAdvice类

package com.iot.proxy.aopframework;

import java.lang.reflect.Method;

/**

* Created by brian on 2016/2/2.

*/

public class MyAdvice implements Advice{

long beginTime = 0 ;

@Override

public void beforeMethod(Method method) {

System.out.println(method.getName()+" before at "+beginTime);

beginTime = System.currentTimeMillis();

}

@Override

public void aftereMethod(Method method) {

long endTime = System.currentTimeMillis();

System.out.println(method.getName()+" cost total "+ (endTime-beginTime));

}

}

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BeanFactory类

package com.iot.proxy.aopframework;

import java.io.IOException;

import java.io.InputStream;

import java.util.Properties;

/**

* Created by brian on 2016/2/2.

*/

public class BeanFactory {

Properties properties = new Properties();

public BeanFactory(InputStream inputStream){

try {

properties.load(inputStream);

} catch (IOException e) {

e.printStackTrace();

}

}

public Object getBean(String name){

String className = properties.getProperty(name);

Object bean = null;

try {

Class clazz = Class.forName(className);

bean = clazz.newInstance();

} catch (ClassNotFoundException e) {

e.printStackTrace();

} catch (InstantiationException e) {

e.printStackTrace();

} catch (IllegalAccessException e) {

e.printStackTrace();

}

if (bean instanceof ProxyFactoryBean){

ProxyFactoryBean proxyFactoryBean = (ProxyFactoryBean)bean;

Advice advice = null;

Object target = null;

try {

advice = (Advice) Class.forName(properties.getProperty(name+".advice")).newInstance();

target = Class.forName(properties.getProperty(name+".target")).newInstance();

} catch (InstantiationException e) {

e.printStackTrace();

} catch (IllegalAccessException e) {

e.printStackTrace();

} catch (ClassNotFoundException e) {

e.printStackTrace();

}

proxyFactoryBean.setAdvice(advice);

proxyFactoryBean.setTarget(target);

Object proxy = ((ProxyFactoryBean) bean).getProxy();

return proxy;

}

return bean;

}

}

ProxyFactoryBean类

package com.iot.proxy.aopframework;

import java.lang.reflect.InvocationHandler;

import java.lang.reflect.Method;

import java.lang.reflect.Proxy;

/**

* Created by brian on 2016/2/3.

*/

public class ProxyFactoryBean {

private Object target;

private Advice advice;

public Object getProxy(){

Object proxy = Proxy.newProxyInstance(

target.getClass().getClassLoader(),

target.getClass().getInterfaces(),

new InvocationHandler() {

@Override

public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {

advice.beforeMethod(method);

Object retVal = method.invoke(target,args);

advice.aftereMethod(method);

return retVal;

}

}

);

return proxy;

}

public Object getTarget() {

return target;

}

public void setTarget(Object target) {

this.target = target;

}

public Advice getAdvice() {

return advice;

}

public void setAdvice(Advice advice) {

this.advice = advice;

}

}

AopFrameWorkTest类

package com.iot.proxy.aopframework;

import java.io.InputStream;

import java.util.Collection;

/**

* Created by brian on 2016/2/3.

*/

public class AopFrameWorkTest {

public static void main(String[] args) {

InputStream inputStream = AopFrameWorkTest.class.getResourceAsStream("config.properties");

Object bean = new BeanFactory(inputStream).getBean("xxx");

System.out.println(bean.getClass().getName());

((Collection) bean).clear();

}

}

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输出

• 配置

xxx=com.iot.proxy.aopframework.ProxyFactoryBean

输出为：

com.sun.proxy.$Proxy0clear before at 0clear cost total 0

• 配置

xxx=java.util.ArrayList

输出为：

java.util.ArrayList

可以看出，只改变配置文件，就可改变代码的运行结果，从而达到灵活的效果