代理模式，JDK动态代理，SpringAOP来龙去脉- fruitking - JavaEye技术网站企业库|免费b2b网站

这里我们学习一下代理模式，JDK的动态代理，以及以JDK为基础的springAOP实现
代理模式：类结构的模式，优点就是不需要更改原有类（被代理类）就能增强原有类（被代理类）的功能，缺点就是必须实现原有类（被代理类）的接口
JDK的动态代理：优点就是不必“复制”原有类（被代理类）接口实现类，缺点就是必须为每个被代理类实现几乎一样的方法
springAOP：优点就是采用springIOC，JDK动态代理等技术来实现AOP机制
我们展示一个类的几个方法，分别采用代理模式，JDK动态代理，springAOP机制来做些额外功能
这里定义一个接口，一个实现类

package com.fruitking.proxy;

/**
 * 汽车服务类接口
 * @author fruitking
 * @since 2010-02-23
 */
public interface CarService {
	
	/**
	 * 启动汽车
	 */
	public void start();
	
	/**
	 * 获得汽车搭载人数
	 * @return
	 */
	public int getLoadAmount();
	
	/**
	 * 设置驾驶员
	 * @param driver
	 * @return
	 */
	public String setDriver(String driver);
	
	/**
	 * 搭载货物
	 * @param goods
	 * @throws NullPointerException
	 * @throws IllegalArgumentException
	 */
	public void loadGoods(String goods)throws NullPointerException,IllegalArgumentException;
}

package com.fruitking.proxy;

/**
 * 汽车服务类接口实现
 * @author fruitking
 * @since 2010-02-23
 */
public class CarServiceImpl implements CarService{
	
	/**
	 * 启动汽车
	 */
	public void start(){
		System.out.println("start my car...");
	}
	
	/**
	 * 获得汽车搭载人数
	 * @return
	 */
	public int getLoadAmount(){
		System.out.println("count the person amount in my car...");
		return 5;
	}
	
	/**
	 * 设置驾驶员
	 * @param driver
	 * @return
	 */
	public String setDriver(String driver){
		System.out.println("driver is:"+driver);
		if(driver==null||"".equals(driver)){
			return "There is not driver.";
		}else{
			return "The driver's name is " + driver + ".";
		}
	}
	
	/**
	 * 搭载货物
	 * @param goods
	 * @throws NullPointerException
	 * @throws IllegalArgumentException
	 */
	public void loadGoods(String goods)throws NullPointerException,IllegalArgumentException{
		if(goods==null||"".equals(goods)){
			throw new NullPointerException("The argument goods is null.");
		}else if("tiger".equals(goods)){
			throw new IllegalArgumentException("The argument goods is invalid.");
		}
		System.out.println("load goods is:"+goods);
	}
}

先来看看代理模式，定义一个代理类，然后调用代理类

package com.fruitking.proxy.pattern;

import com.fruitking.proxy.CarService;

/**
 * 汽车服务类接口的代理类实现
 * @author fruitking
 * @since 2010-02-23
 */
public class CarServiceProxy implements CarService {
	
	private CarService carServiceTarget;//被代理的目标类
	
	/**
	 * 在构造函数中设置被代理的目标类
	 * 也可以使用set方法设置被代理的目标类
	 * @param carServiceTarget
	 */
	public CarServiceProxy(CarService carServiceTarget){
		this.carServiceTarget = carServiceTarget;
	}

	/**
	 * 启动汽车
	 */
	public void start(){
		System.out.println("before excute target object...");
		carServiceTarget.start();
		System.out.println("after excute target object...");
	}
	
	/**
	 * 获得汽车搭载人数
	 * @return
	 */
	public int getLoadAmount(){
		System.out.println("before excute target object...");
		int amount = carServiceTarget.getLoadAmount();
		System.out.println("after excute target object...");
		return amount;
	}
	
	/**
	 * 设置驾驶员
	 * @param driver
	 * @return
	 */
	public String setDriver(String driver){
		System.out.println("before excute target object...");
		String resultObject = carServiceTarget.setDriver(driver);
		System.out.println("after excute target object...");
		return resultObject;
	}
	
	/**
	 * 搭载货物
	 * @param goods
	 * @throws NullPointerException
	 * @throws IllegalArgumentException
	 */
	public void loadGoods(String goods)throws NullPointerException,IllegalArgumentException{
		//这里不实现任何操作
	}
}

package com.fruitking.proxy.pattern;

import com.fruitking.proxy.CarService;
import com.fruitking.proxy.CarServiceImpl;

public class TestProxyPattern {

	/**
	 * 代理模式中的调用
	 * @param args
	 */
	public static void main(String[] args) {
		CarService carServiceTarget = new CarServiceImpl();
		CarServiceProxy carServiceProxy = new CarServiceProxy(carServiceTarget);
		//执行代理类的方法
		//作用一：间接执行被代理类的方法，
		//作用二：代理类可以在被代理类方法执行前后做一些额外操作
		//总结：不更改原有类的功能和程序代码情况下，实现额外的功能能
		//缺点：要为每个被代理类编写一个代理类，且需要实现相同接口的所有方法
		carServiceProxy.start();
		carServiceProxy.getLoadAmount();
		String driver = carServiceProxy.setDriver("fruitking");
		System.out.println(driver);
	}
}

再来看看JDK动态代理

package com.fruitking.proxy.jdkdproxy;

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

import com.fruitking.proxy.CarService;

/**
 * java动态代理实现类
 * @author fruitking
 * @since 2010-02-23
 */
public class CarServiceJDKDynamicProxy implements InvocationHandler {

	private CarService carServiceTarget;//被代理的目标类
	
	/**
	 * 在构造函数中设置被代理的目标类
	 * 也可以使用set方法设置被代理的目标类
	 * @param carServiceTarget
	 */
	public CarServiceJDKDynamicProxy(CarService carServiceTarget){
		this.carServiceTarget = carServiceTarget;
	}
	
	public Object invoke(Object proxy, Method method, Object[] args)
			throws Throwable {
		System.out.println("before excute target object...");
		Object object = method.invoke(this.carServiceTarget,args);
		System.out.println("after excute target object...");
		return object;
	}
}

package com.fruitking.proxy.jdkdproxy;

import java.lang.reflect.Proxy;

import com.fruitking.proxy.CarService;
import com.fruitking.proxy.CarServiceImpl;

public class TestJDKDynamicProxy {

	/**
	 * JDK中动态代理技术中的代理调用
	 * @param args
	 */
	public static void main(String[] args) {
		CarService carServiceTarget = new CarServiceImpl();
		CarServiceJDKDynamicProxy carServiceJDKDynamicProxyTarget = new CarServiceJDKDynamicProxy(carServiceTarget);
		CarService carServiceProxy = (CarService)Proxy.newProxyInstance(carServiceTarget.getClass().getClassLoader(),new Class[]{CarService.class}, carServiceJDKDynamicProxyTarget);
		//执行代理类的方法
		//作用一：间接执行被代理类的方法，
		//作用二：代理类可以在被代理类方法执行前后做一些额外操作
		//总结：不更改原有类的功能和程序代码情况下，实现额外的功能能
		//缺点：要为每个被代理类编写一个代理类，且具有相同的接口
		carServiceProxy.start();
		carServiceProxy.getLoadAmount();
		String driver = carServiceProxy.setDriver("fruitking");
		System.out.println(driver);
	}

}

{zh1}来看看spring的AOP机制的实现

package com.fruitking.proxy.springaop;

import java.lang.reflect.Method;

import org.springframework.aop.MethodBeforeAdvice;

/**
 * 使用spring的AOP机制的事前通知接口实现
 * @author fruitking
 * @since 2010-02-23
 */
public class CarServiceBeforeAdvice implements MethodBeforeAdvice{
	
	public void before(Method method, Object[] args, Object target)throws Throwable {
		System.out.println("before excute target object...");
		String methodName = method.getName();  //得到方法名 
		String targetClassName = target.getClass().getName();//得到调用类名
		System.out.println(targetClassName+"."+methodName+"()");
	}
}

package com.fruitking.proxy.springaop;

import java.lang.reflect.Method;

import org.springframework.aop.AfterReturningAdvice;

/**
 * 使用spring的AOP机制的事前通知接口实现
 * @author fruitking
 * @since 2010-02-23
 */
public class CarServiceAfterAdvice implements AfterReturningAdvice {

	public void afterReturning(Object returnValue,Method method,Object[] args,Object target)throws Throwable{
		String methodName = method.getName();  //得到方法名 
		String targetClassName = target.getClass().getName();//得到调用类名
		System.out.println(targetClassName+"."+methodName+"()");
		System.out.println("after excute target object...");
	}
}

package com.fruitking.proxy.springaop;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;

/**
 * 使用spring的AOP机制的事前通知接口实现
 * @author fruitking
 * @since 2010-02-23
 */
public class CarServiceAroundAdvice implements MethodInterceptor {
	
	public Object invoke(MethodInvocation invocation) throws Throwable {
		System.out.println("before around excute target object...");
		String methodName = invocation.getMethod().getName();  //得到方法名 
		String targetClassName = invocation.getClass().getName();//得到调用类名
		System.out.println(targetClassName+"."+methodName+"()");
		Object result = invocation.proceed(); //调用横切点，即真实操作
		System.out.println("after around excute target object...");
		return result;
	}
}

package com.fruitking.proxy.springaop;

import org.springframework.aop.ThrowsAdvice;

/**
 * 使用spring的AOP机制的事前通知接口实现
 * @author fruitking
 * @since 2010-02-23
 */
public class CarServiceThrowsAdvice implements ThrowsAdvice {
	
	public void afterThrowing(NullPointerException e){//可以定义多个方法，只要传入的参数是不同异常
		System.out.print("not load anything goods!");
	}
	
	public void afterThrowing(IllegalArgumentException e){//可以定义多个方法，只要传入的参数是不同异常
		System.out.print("load a tiger,it's very much dangerous!");
	}

}

spring的配置文件，把这些使用IOC处理

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN 2.0//EN" "http://www.springframework.org/dtd/spring-beans-2.0.dtd">
<beans>
	
	<bean id="carServiceTarget" class="com.fruitking.proxy.CarServiceImpl"/>
	 
	<bean id="carServiceBeforeAdvice" class="com.fruitking.proxy.springaop.CarServiceBeforeAdvice"/>
	
	<bean id="carServiceAfterAdvice" class="com.fruitking.proxy.springaop.CarServiceAfterAdvice"/>
	
	<bean id="carServiceAroundAdvice" class="com.fruitking.proxy.springaop.CarServiceAroundAdvice"/>
	
	<bean id="carServiceThrowsAdvice" class="com.fruitking.proxy.springaop.CarServiceThrowsAdvice"/>
    
    <bean id="carService" class="org.springframework.aop.framework.ProxyFactoryBean"> 
        <property name="proxyInterfaces" value="com.fruitking.proxy.CarService"/> 
        <property name="target" ref="carServiceTarget"/> 
        <property name="interceptorNames"> 
            <list> 
                <value>carServiceBeforeAdvice</value>
                <value>carServiceAfterAdvice</value>
                <value>carServiceAroundAdvice</value>
                <value>carServiceThrowsAdvice</value>
            </list> 
        </property>
    </bean>
    
</beans>

package com.fruitking.proxy.springaop;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.fruitking.proxy.CarService;

public class TestSpringAOP {

	/**
	 * 利用spring的AOP机制实现“代理”的横向抽取机制方式
	 * @param args
	 */
	public static void main(String[] args) {
		ApplicationContext ctx=new ClassPathXmlApplicationContext("beans.xml"); 
		CarService carService = (CarService) ctx.getBean("carService");
		carService.start();
		carService.getLoadAmount();
		String driver = carService.setDriver("fruitking");
		System.out.println(driver);
		System.out.println("------------------------------");
		carService.loadGoods("Miss Mary");
		System.out.println("------------------------------");
		try{
			carService.loadGoods(null);
		}catch(NullPointerException e){
			e.printStackTrace();
		}
		System.out.println("------------------------------");
		try{
			carService.loadGoods("tiger");
		}catch(IllegalArgumentException e){
			e.printStackTrace();
		}
	}

}

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