众所周知，spring aop中一个advisor=advice or methodinterceptor + pointcut，之后将不同的advisor调用ProxyFactory的addAdvisor方法添加进去并排序（顺序特别重要，在最新的源码里是需要实现PriorityOrdered接口或者使用@Order注解来实现），最后调用ProxyFactory的getProxy方法得到增强，在看spring源码的时候偶尔注意到了一系列introduction和mixin的概念，附上一篇非常nice的博文：http://www.javalobby.org/java/forums/t45691.html

废话不多说，上代码：

package com.rabbit.spring.aop.introduction;import org.springframework.aop.IntroductionAdvisor;import org.springframework.aop.framework.ProxyFactory;public class IntroductionExample {	public static void main(String[] args) {		TargetBean target = new TargetBean();		target.setName("Ethan");				IntroductionAdvisor advisor = new IsModifiedAdvisor();				ProxyFactory pf = new ProxyFactory();		pf.setTarget(target);		pf.addAdvisor(advisor);		pf.setOptimize(true);				TargetBean proxy = (TargetBean) pf.getProxy();		IsModified proxyInterface = (IsModified) proxy;				System.out.println("is target bean " + (proxy instanceof TargetBean));		System.out.println("is ismodified " + (proxy instanceof IsModified));		System.out.println("changed? " + proxyInterface.isModified());				proxy.setName("Zhang");		System.out.println("changed? " + proxyInterface.isModified());		proxy.setName("Li");		System.out.println("changed? " + proxyInterface.isModified());	}}

package com.rabbit.spring.aop.introduction;public interface IsModified {	boolean isModified();}

package com.rabbit.spring.aop.introduction;import org.springframework.aop.support.DefaultIntroductionAdvisor;public class IsModifiedAdvisor extends DefaultIntroductionAdvisor {	/**	 * 	 */	private static final long serialVersionUID = 1L;	public IsModifiedAdvisor() {		super(new IsModifiedMixin());	}}

package com.rabbit.spring.aop.introduction;import java.lang.reflect.Method;import java.util.Map;import java.util.concurrent.ConcurrentHashMap;import org.aopalliance.intercept.MethodInvocation;import org.springframework.aop.support.DelegatingIntroductionInterceptor;public class IsModifiedMixin extends DelegatingIntroductionInterceptor implements IsModified {	/**	 * 	 */	private static final long serialVersionUID = 1L;	private boolean isModified = false;    private Map
    
      methodCache = new ConcurrentHashMap<>();        @Override    public boolean isModified() {        return isModified;    }        public Object invoke(MethodInvocation invocation) throws Throwable {        if (!isModified) {            if ((invocation.getMethod().getName().startsWith("set"))                    && (invocation.getArguments().length == 1)) {                Method getter = getGetter(invocation.getMethod());                if (getter != null) {                    Object newVal = invocation.getArguments()[0];                    Object oldVal = getter.invoke(invocation.getThis(), null);                                        if((newVal == null) && (oldVal == null)) {                        isModified = false;                    } else if((newVal == null) && (oldVal != null)) {                        isModified = true;                    } else if((newVal != null) && (oldVal == null)) {                        isModified = true;                    } else {                        isModified = (!newVal.equals(oldVal));                    }                }            }        }        return super.invoke(invocation);    }    private Method getGetter(Method setter) {        Method getter = methodCache.get(setter);        if (getter != null) {            return getter;        }        String getterName = setter.getName().replaceFirst("set", "get");        try {            getter = setter.getDeclaringClass().getMethod(getterName, (Class
     []) null);            methodCache.put(setter, getter);            return getter;        } catch (NoSuchMethodException ex) {            return null;        }    }}
    

package com.rabbit.spring.aop.introduction;public class TargetBean {	/**	 * @return the name	 */	public String getName() {		return name;	}	/**	 * @param name the name to set	 */	public void setName(String name) {		this.name = name;	}	private String name;	}

is target bean true

is ismodified true

changed? false

changed? true

changed? true

github地址：https://github.com/stillotherguy/javaopensource/tree/master/src/main/java/com/rabbit/spring/aop/introduction

可以自己copy一份运行一下，要想知道其中奥秘，spring aop源码是必须了解的，以后有空写一下！