MINA学习笔记——奇怪的处理器DemuxingIoHandler

初次接触MINA，看了看多处理器的代码，发现一些有意思的现象，按说写Apache框架的这些人都是高手的，怎么会犯这样的错，下面是DemuxingIoHandler的部分说明。这个类中有个方法要用深度优先遍历一颗继承树。

Consider the following type hierarchy (Cx are classes while Ix are interfaces): 

     C3 - I7 - I9
      |    |   /\
      |   I8  I3 I4
      |
     C2 - I5 - I6
      |
     C1 - I1 - I2 - I4
      |         |
      |        I3
    Object          
 
When message is of type C3 this hierarchy will be searched in the following order: C3, I7, I8, I9, I3, I4, C2, I5, I6, C1, I1, I2, I3, I4, Object. 

I7 既然是C3 的接口，从图中可以看出I8, I9, I3, I4 都是接口，那么I7 怎么可以继承2个接口，如果是实现I8 和I9，那I7 怎么还可能是接口？好奇怪的现象。。

下边是这个深度优先遍历的实现：

    private final Map<Class, MessageHandler> type2handler
             = new Hashtable<Class, MessageHandler>();
    private MessageHandler<Object> findHandler( Class type, Set<Class> triedClasses )
    {
        MessageHandler handler = null;

        if( triedClasses != null && triedClasses.contains( type ) )
            return null;

        /*
         * Try the registered handlers for an immediate match.
         */
        handler = type2handler.get( type );
        
        if( handler == null )
        {
            /*
             * No immediate match could be found. Search the type's interfaces.
             */
            
            if( triedClasses == null )
                triedClasses = new IdentityHashSet<Class>();
            triedClasses.add( type );
            
            Class[] interfaces = type.getInterfaces();
            for( int i = 0; i < interfaces.length; i ++ )
            {
                handler = findHandler( interfaces[ i ], triedClasses );
                if( handler != null )
                    break;
            }
        }
        
        if( handler == null )
        {
            /*
             * No match in type's interfaces could be found. Search the 
             * superclass.
             */
            
            Class superclass = type.getSuperclass();
            if( superclass != null )
                handler = findHandler( superclass );
        }
        
        /*
         * Make sure the handler is added to the cache. By updating the cache
         * here all the types (superclasses and interfaces) in the path which 
         * led to a match will be cached along with the immediate message type.
         */
        if( handler != null )
            findHandlerCache.put( type, handler );
        
        return handler;
    }