org.perfectjpattern.core.behavioral.chainofresponsibility
Class AbstractHandler<R>

java.lang.Object
  org.perfectjpattern.core.behavioral.chainofresponsibility.AbstractHandler<R>

Type Parameters:

R - Request parameter type

All Implemented Interfaces:

IHandler<R>

Direct Known Subclasses:

AbstractParameterlessHandler

public abstract class AbstractHandler<R>
extends Object
implements IHandler<R>

Abstract reusable implementation of IHandler interface.

The Default Strategy is OnlyOneHandleStrategy same as in GoF.

Version:

$Revision: 1.0 $ $Date: Jun 23, 2007 1:31:27 PM $

Author:

Giovanni Azua

See Also:

IHandler, NullHandler

Constructor Summary

AbstractHandler()
Constructs a AbstractHandler from a NullHandler

AbstractHandler(IHandler<R> aSuccessor)
Constructs a AbstractHandler from a Successor

Method Summary

boolean	canHandle(R aRequest) Returns true if this IHandler can handle the given request, false otherwise.
IHandler<R>	getSuccessor() Returns the Successor handler.
void	handle(R aRequest) Handle the given request.
void	setChainStrategy(IChainStrategy aStrategy) Set the IChainStrategy to this IHandler.
void	setSuccessor(IHandler<R> aSuccessor) Sets the Successor element.
void	start(R aRequest) Triggers execution of the Chain if the target Handler is the first reference, otherwise implements the decision-making regarding forwarding the request to its successor IHandler instance.

Methods inherited from class java.lang.Object

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

Constructor Detail

AbstractHandler

public AbstractHandler()

Constructs a AbstractHandler from a NullHandler

AbstractHandler

public AbstractHandler(IHandler<R> aSuccessor)
                throws IllegalArgumentException

Constructs a AbstractHandler from a Successor

Parameters:

aSuccessor - Successor handler.

Throws:

IllegalArgumentException - 'aSuccessor' must not be null.

Method Detail

start

public final void start(R aRequest)
                 throws IllegalArgumentException

Triggers execution of the Chain if the target Handler is the first reference, otherwise implements the decision-making regarding forwarding the request to its successor IHandler instance.

Specified by:

start in interface IHandler<R>

Parameters:

aRequest - Context-specific request to handle.

Throws:

IllegalArgumentException - 'aRequest' must not be null.

getSuccessor

public final IHandler<R> getSuccessor()

Returns the Successor handler.

Specified by:

getSuccessor in interface IHandler<R>

Returns:

Successor handler.

canHandle

public boolean canHandle(R aRequest)
                  throws IllegalArgumentException

Returns true if this IHandler can handle the given request, false otherwise.

Specified by:

canHandle in interface IHandler<R>

Parameters:

aRequest - Context-specific request to handle.

Returns:

true if this IHandler can handle the given request, false otherwise.

Throws:

IllegalArgumentException - 'aRequest' must not be null.

handle

public void handle(R aRequest)
            throws IllegalArgumentException

Handle the given request. Implements the actual handling logic and must not contain any decision-making regarding e.g. forwarding the request.

Specified by:

handle in interface IHandler<R>

Parameters:

aRequest - Context-specific request to handle.

Throws:

IllegalArgumentException - 'aRequest' must not be null.

setSuccessor

public final void setSuccessor(IHandler<R> aSuccessor)
                        throws IllegalArgumentException

Sets the Successor element.

Specified by:

setSuccessor in interface IHandler<R>

Parameters:

aSuccessor - Successor handler

Throws:

IllegalArgumentException - 'aSuccessor' must not be null.

setChainStrategy

public final void setChainStrategy(IChainStrategy aStrategy)
                            throws IllegalArgumentException

Set the IChainStrategy to this IHandler. IChainStrategy allows to easily modify how the Chain should behave. Possible implementations are e.g.

• Halt as soon as the first Handler processes the request
• Let all handlers process the request
• Let the first N handlers process the request

Specified by:

setChainStrategy in interface IHandler<R>

Parameters:

aStrategy - Continuation strategy defines how the chain should behave

Throws:

IllegalArgumentException - 'aStrategy' must not be null.