org.apache.commons.betwixt.expression

Class MethodExpression

java.lang.Object

org.apache.commons.betwixt.expression.MethodExpression

All Implemented Interfaces:

Expression

public class MethodExpression
extends Object
implements Expression

MethodExpression evaluates a method on the current bean context.

Version:

$Revision: 1.4 $

Author:

James Strachan

Field Summary

Fields

Modifier and Type	Field and Description
private Method	method The method to call on the bean
protected static Object[]	NULL_ARGUMENTS null arguments
protected static Class[]	NULL_CLASSES null classes

Constructor Summary

Constructors

Constructor and Description
MethodExpression() Base constructor
MethodExpression(Method method) Convenience constructor sets method property

Method Summary

Methods

Modifier and Type	Method and Description
Object	evaluate(Context context) Evaluate by calling the read method on the current bean
protected Method	findAlternateMethod(Class type, Method method) Tries to find an alternate method for the given type using interfaces which gets around the problem of inner classes, such as on Map.Entry implementations.
protected Object[]	getArguments() Allows derived objects to create arguments for the method call
Method	getMethod() Gets the method used to evaluate this expression.
protected void	handleException(Context context, Exception e) Log error to context's logger.
void	setMethod(Method method) Sets the method used to evaluate this expression
String	toString() Returns something useful for logging.
void	update(Context context, String newValue) Do nothing.

Methods inherited from class java.lang.Object

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

Field Detail

NULL_ARGUMENTS

protected static Object[] NULL_ARGUMENTS

null arguments

NULL_CLASSES

protected static Class[] NULL_CLASSES

null classes

method

private Method method

The method to call on the bean

Constructor Detail

MethodExpression

public MethodExpression()

Base constructor

MethodExpression

public MethodExpression(Method method)

Convenience constructor sets method property

Parameters:

method - the Method whose return value when invoked on the bean will the value of this expression

Method Detail

evaluate

public Object evaluate(Context context)

Evaluate by calling the read method on the current bean

Specified by:

evaluate in interface Expression

Parameters:

context - the context against which this expression will be evaluated

Returns:

the value returned by the method when it's invoked on the context's bean, so long as the method can be invoked. Otherwise, null.

update

public void update(Context context,
          String newValue)

Do nothing.

Specified by:

update in interface Expression

Parameters:

context - update this Context

newValue - the new value for this expression

See Also:

Expression

getMethod

public Method getMethod()

Gets the method used to evaluate this expression.

Returns:

the method whose value (when invoked against the context's bean) will be used to evaluate this expression.

setMethod

public void setMethod(Method method)

Sets the method used to evaluate this expression

Parameters:

method - method whose value (when invoked against the context's bean) will be used to evaluate this expression

getArguments

protected Object[] getArguments()

Allows derived objects to create arguments for the method call

Returns:

NULL_ARGUMENTS

findAlternateMethod

protected Method findAlternateMethod(Class type,
                         Method method)

Tries to find an alternate method for the given type using interfaces which gets around the problem of inner classes, such as on Map.Entry implementations.

Parameters:

type - the Class whose methods are to be searched

method - the Method for which an alternative is to be search for

Returns:

the alternative Method, if one can be found. Otherwise null.

handleException

protected void handleException(Context context,
                   Exception e)

Log error to context's logger.

Allows derived objects to handle exceptions differently.

Parameters:

context - the Context being evaluated when the exception occured

e - the exception to handle

toString

public String toString()

Returns something useful for logging.

Overrides:

toString in class Object

Returns:

something useful for logging