dk.rode.thesis.chainofresponsibility
Class AbstractHandlerChain<R>

java.lang.Object
  dk.rode.thesis.chainofresponsibility.AbstractHandlerChain<R>

Type Parameters:

R - The type of requests handled by this chain.

All Implemented Interfaces:

Handler<R>, HandlerChain<R>, HandlerLink<R>

Direct Known Subclasses:

StandardHandlerChain, WeakHandlerChain

public abstract class AbstractHandlerChain<R>
extends Object
implements HandlerChain<R>

An abstract handler chain implements the basic traits of the HandlerChain interface.

Author:

Gunni Rode / rode.dk

Constructor Summary

protected

AbstractHandlerChain() No-arg constructor.

Method Summary

Handler<R>	forward(R request, Handler<R> current) Forwards the the request supplied as request to the handler represented by this link.
Handler<R>	handle(R request) Handles the request supplied as request by forwarding it to each handler in this chain until a handler can handle it, starting from the first registered handler.
Handler<R>	handle(R request, HandlerLink<R> link) Handles the request supplied as request or forwards it to the next handler in the chain represented by the handler link supplied as link, if any.
String	toString() Returns the string representation of this handler chain.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface dk.rode.thesis.chainofresponsibility.HandlerChain

getHandlers, isRegistered, register, size, unregister

Constructor Detail

AbstractHandlerChain

protected AbstractHandlerChain()

No-arg constructor.

Method Detail

forward

public Handler<R> forward(R request,
                          Handler<R> current)

Description copied from interface: HandlerLink

Forwards the the request supplied as request to the handler represented by this link.

The next handler is the handler after current in the chain. current can be located at any place in the chain, and if not found, all handlers in the chain are tried.

Specified by:

forward in interface HandlerLink<R>

Parameters:

request - The request to handle; nullability determined by the actual handler implementation.

current - The handler in the chain that could not handle request; can be null if this link represents the first handler in the chain.

Returns:

The handler that handled request, if any. Can be null.

handle

public Handler<R> handle(R request)

Handles the request supplied as request by forwarding it to each handler in this chain until a handler can handle it, starting from the first registered handler.

The handlers used are those delivered by HandlerChain.getHandlers(Handler) with a null argument.

Specified by:

handle in interface HandlerChain<R>

Parameters:

request - The request to handle. This chain allows it to be null, but individual handlers may not.

Returns:

The handler that handled request, if any; may be null.

handle

public Handler<R> handle(R request,
                         HandlerLink<R> link)

Description copied from interface: Handler

Handles the request supplied as request or forwards it to the next handler in the chain represented by the handler link supplied as link, if any. link can be null, in which case this handler is considered the last handler in the chain.

If this handler handles request, this handler is returned. If this handler cannot handle request, the result from handling the request using link is returned. Finally, if link is null, null is returned.

Specified by:

handle in interface Handler<R>

Parameters:

request - The request to handle; nullability determined by the actual handler implementation.

link - The link to the next handler in the current chain; can be null.

Returns:

The handler that handled request, if any. Can be null.

toString

public String toString()

Returns the string representation of this handler chain.

Overrides:

toString in class Object

Returns:

The string representation; never null.