java基礎鞏固筆記(4)-實現AOP功能的封裝與配置的小框架

java基礎鞏固筆記(4)-實現AOP功能的封裝與配置的小框架

標籤： java

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本文經過是動態代理實現的AOP功能的封裝與配置的小框架.加深對動態代理和AOP編程的理解

設計

根據配置文件的鍵xxx對應的值(類全名)建立相應類的對象。

當且僅當xxx對應的值爲com.iot.proxy.aopframework.ProxyFactoryBean時，則生成相應的動態代理類對象。代理對象的目標類和通知實現類分別由xxx.target和xxx.advice配置

配置文件

config.propertiest位於aopframework包下

• xxx表明要加載的類
• xxx.advice表明通知接口的某個實現類
• xxx.target表明委託類

#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,有以下幾個類/接口：

• BeanFactory,用於讀取配置文件，根據配置建立相應的對象
• ProxyFactoryBean,用於生成代理對象，含有兩個私有屬性:目標和通知
• Advice,通知接口，用於把切面的代碼以對象的形式傳遞給InvocationHandler的的invoke方法
• MyAdvice,Advice接口的一個實現類，打印執行方法前的時間及執行耗時
• AopFrameWorkTest，測試效果

代碼

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類

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類

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類

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類

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();
    }
}

輸出

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

輸出爲：

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

• 配置xxx=java.util.ArrayList

輸出爲：

java.util.ArrayList

能夠看出，只改變配置文件，就可改變代碼的運行結果，從而達到靈活的效果

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