org.apache.commons.chain.generic
Class DispatchCommand

java.lang.Object
  extended by org.apache.commons.chain.generic.DispatchCommand
All Implemented Interfaces:
Command

public abstract class DispatchCommand
extends java.lang.Object
implements Command

An abstract base command which uses introspection to look up a method to execute. For use by developers who prefer to group related functionality into a single class rather than an inheritance family.

Since:
Chain 1.1

Field Summary
protected static java.lang.Class[] DEFAULT_SIGNATURE
          The base implementation expects dispatch methods to take a Context as their only argument.
private  java.lang.String method
          Method name
private  java.lang.String methodKey
          Method key
private  java.util.Map methods
          Cache of methods
 
Fields inherited from interface org.apache.commons.chain.Command
CONTINUE_PROCESSING, PROCESSING_COMPLETE
 
Constructor Summary
DispatchCommand()
           
 
Method Summary
protected  boolean evaluateResult(java.lang.Object o)
          Evaluate the result of the method invocation as a boolean value.
 boolean execute(Context context)
          Look up the method specified by either "method" or "methodKey" and invoke it, returning a boolean value as interpreted by evaluateResult.
protected  java.lang.reflect.Method extractMethod(Context context)
          Extract the dispatch method.
protected  java.lang.Object[] getArguments(Context context)
          Get the arguments to be passed into the dispatch method.
 java.lang.String getMethod()
          Return the method name.
 java.lang.String getMethodKey()
          Return the Context key for the method name.
protected  java.lang.Class[] getSignature()
          Return a Class[] describing the expected signature of the method.
 void setMethod(java.lang.String method)
          Set the method name.
 void setMethodKey(java.lang.String methodKey)
          Set the Context key for the method name.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

methods

private java.util.Map methods
Cache of methods


method

private java.lang.String method
Method name


methodKey

private java.lang.String methodKey
Method key


DEFAULT_SIGNATURE

protected static final java.lang.Class[] DEFAULT_SIGNATURE
The base implementation expects dispatch methods to take a Context as their only argument.

Constructor Detail

DispatchCommand

public DispatchCommand()
Method Detail

execute

public boolean execute(Context context)
                throws java.lang.Exception
Look up the method specified by either "method" or "methodKey" and invoke it, returning a boolean value as interpreted by evaluateResult.

Specified by:
execute in interface Command
Parameters:
context - The Context to be processed by this Command.
Returns:
the result of method being dispatched to.
Throws:
java.lang.IllegalStateException - if neither 'method' nor 'methodKey' properties are defined
java.lang.Exception - if any is thrown by the invocation. Note that if invoking the method results in an InvocationTargetException, the cause of that exception is thrown instead of the exception itself, unless the cause is an Error or other Throwable which is not an Exception.

extractMethod

protected java.lang.reflect.Method extractMethod(Context context)
                                          throws java.lang.NoSuchMethodException
Extract the dispatch method. The base implementation uses the command's method property as the name of a method to look up, or, if that is not defined, looks up the the method name in the Context using the methodKey.

Parameters:
context - The Context being processed by this Command.
Returns:
The method to execute
Throws:
java.lang.NoSuchMethodException - if no method can be found under the specified name.
java.lang.NullPointerException - if no methodName cannot be determined

evaluateResult

protected boolean evaluateResult(java.lang.Object o)
Evaluate the result of the method invocation as a boolean value. Base implementation expects that the invoked method returns boolean true/false, but subclasses might implement other interpretations.

Parameters:
o - The result of the methid execution
Returns:
The evaluated result/

getSignature

protected java.lang.Class[] getSignature()
Return a Class[] describing the expected signature of the method.

Returns:
The method signature.

getArguments

protected java.lang.Object[] getArguments(Context context)
Get the arguments to be passed into the dispatch method. Default implementation simply returns the context which was passed in, but subclasses could use this to wrap the context in some other type, or extract key values from the context to pass in. The length and types of values returned by this must coordinate with the return value of getSignature()

Parameters:
context - The Context being processed by this Command.
Returns:
The method arguments.

getMethod

public java.lang.String getMethod()
Return the method name.

Returns:
The method name.

getMethodKey

public java.lang.String getMethodKey()
Return the Context key for the method name.

Returns:
The Context key for the method name.

setMethod

public void setMethod(java.lang.String method)
Set the method name.

Parameters:
method - The method name.

setMethodKey

public void setMethodKey(java.lang.String methodKey)
Set the Context key for the method name.

Parameters:
methodKey - The Context key for the method name.