Spring 中 Around AOP 实现了 ThrowsAdvice 接口后，为什么必须写一个方法名是 afterThrowing 的方法？

Spring 中 Around AOP 实现了 ThrowsAdvice 接口后，为什么必须写一个方法名是 afterThrowing 的方法？
不然会报错：
At least one handler method must be found in class
，既然如此，这个方法为什么不在接口里定义呢？
熟悉Spring的人讲讲。

[code="java"]
package hello;

import org.springframework.aop.ThrowsAdvice;

public class LoggingThrowsAdvice implements ThrowsAdvice{

public  void  afterThrowing(Exception  ex)  throws  Throwable{
    LogUtil.log.debug("shen  he  shu  ju  you  yi  chang...");
} 

}

[/code]

看看它的源码，什么都清楚了

[code="java"]
/**

• Tag interface for throws advice. *

• There are not any methods on this interface, as methods are invoked by reflection. //反正spring它内部自己知道用反射来匹配调用这个方法名的方法就行了， Implementing classes must implement methods of the form:
  

• void afterThrowing([Method, args, target], ThrowableSubclass);

• Some examples of valid methods would be:

• 这里有4个方法，也就是支持4种方式，如果都定义在接口里，用户实现接口那必然
• 要把4个方法都实现，（但却只需要用一个方法时）很冗余吧，所以就干脆定义成标识接口

• public void afterThrowing(Exception ex)

• public void afterThrowing(RemoteException)

• public void afterThrowing(Method method, Object[] args, Object target, Exception ex)

• public void afterThrowing(Method method, Object[] args, Object target, ServletException ex)

  *

• The first three arguments are optional, and only useful if

• we want further information about the joinpoint, as in AspectJ
• after throwing advice. *
• @author Rod Johnson
• @see AfterReturningAdvice
• @see MethodBeforeAdvice */ public interface ThrowsAdvice extends AfterAdvice {

}

[/code]

便于以后升级,扩展吧,同下兼容.