SpringAOP中的IntroductionInterceptor

        Introduction（引入）是个特别的Advice，类通过实现AOP中的org.springframework.aop.IntroductionInterceptor在不改变原有方法的基础上却可以增加新的方法。IntroductionInterceptor继承了MethodInterceptor和DynamicIntroductionAdvice接口，其中implementsInterface()方法（继承自DynamicIntroductionAdvice）如果返回true，表示目前的 IntroductionInterceptor实现了给定的接口（也就是要额外增加行为的接口），此时要使用invoke()调用该接口上的方法，让目标执行额外的行为。需要注意的是不可能使用MethodInvocation的proceed()方法，因为要执行的是类原来没有的行为，proceed()方法没有意义。

示例：需要导入aopalliance-1.0.jar和spring-aop-2.5.1.jar

目标接口：

package com.yourcompany.spring;public interface ISome {public void doSome();}

package com.yourcompany.spring;public class Some implements ISome{	public void doSome(){		System.out.println("原来Some对象的功能...");	}}

package com.yourcompany.spring;public interface IOther{	public void doOther();}

package com.yourcompany.spring;import org.aopalliance.intercept.MethodInvocation;import org.springframework.aop.IntroductionInterceptor;public class Other implements IntroductionInterceptor,IOther{	public void doOther(){		System.out.println("Other对象的功能");	}	public Object invoke(MethodInvocation methodInvocation) throws Throwable {		if(implementsInterface(methodInvocation.getMethod().getDeclaringClass())){			retu methodInvocation.getMethod().invoke(this, methodInvocation.getArguments());		}		else{			retu methodInvocation.proceed();		}	}	public boolean implementsInterface(Class arg0){		boolean assignableFrom = arg0.isAssignableFrom(IOther.class);		retu assignableFrom;	}	}

<?xml version="1.0" encoding="UTF-8"?><beans	xmlns="http://www.springframework.org/schema/beans"	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd">	<bean id="some" class="com.yourcompany.spring.Some" />	<bean id="other" class="com.yourcompany.spring.Other" />	<bean id="otherAdvisor" class="org.springframework.aop.support.DefaultIntroductionAdvisor">		<constructor-arg ref="other"></constructor-arg>		<constructor-arg value="com.yourcompany.spring.IOther" />	</bean>	<bean id="proxyFactoryBean" class="org.springframework.aop.framework.ProxyFactoryBean">		<property name="proxyInterfaces" value="com.yourcompany.spring.ISome" />		<property name="target" ref="some" />		<property name="interceptorNames">			<list>				<value>otherAdvisor</value>			</list>		</property>	</bean></beans>

程序主入口：

package com.yourcompany.spring;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;public class Introduction{	public static void main(String[] args) {		ApplicationContext context=new ClassPathXmlApplicationContext("applicationContext.xml");	ISome some=(ISome)context.getBean("proxyFactoryBean");	some.doSome();	((IOther)some).doOther();	}}

另：Spring框架中的类DelegatingIntroductionInterceptor是接口DelegatingIntroductionInterceptor的默认实现类，用法大致相同。