Java实现AOP功能的封装与配置的小框架实例代码

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

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

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));
	}
}

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();
	}
}

输出

• 配置xxx=com.iot.proxy.aopframework.ProxyFactoryBean
  

输出为：

com.sun.proxy.$Proxy0
clear before at 0
clear 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

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