org.apache.commons.jexl
Class ExpressionImpl

java.lang.Object
  org.apache.commons.jexl.ExpressionImpl

All Implemented Interfaces:

Expression

class ExpressionImpl

extends java.lang.Object

implements Expression

Instances of ExpressionImpl are created by the ExpressionFactory, and this is the default implementation of the Expression interface.

Version:

$Id: ExpressionImpl.java,v 1.11 2004/08/23 14:00:11 dion Exp $

Author:

Geir Magnusson Jr.

Field Summary

protected java.lang.String	expression Original expression - this is just a 'snippet', not a valid statement (i.e.
protected SimpleNode	node The resulting AST we can call value() on
protected java.util.List	postResolvers
protected java.util.List	preResolvers

Constructor Summary

(package private)

ExpressionImpl(java.lang.String expr, SimpleNode ref) do not let this be generally instantiated with a 'new'

Method Summary

void	addPostResolver(JexlExprResolver resolver) allows addition of a resolver to allow custom interdiction of expression evaluation
void	addPreResolver(JexlExprResolver resolver) allows addition of a resolver to allow custom interdiction of expression evaluation
java.lang.Object	evaluate(JexlContext context) Evaluate the expression and return the value.
java.lang.String	getExpression() returns original expression string
protected java.lang.Object	tryResolver(java.util.List resolverList, JexlContext context) Tries the resolvers in the given resolverlist against the context

Methods inherited from class java.lang.Object

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

Field Detail

preResolvers

protected java.util.List preResolvers

postResolvers

protected java.util.List postResolvers

expression

protected java.lang.String expression

Original expression - this is just a 'snippet', not a valid statement (i.e. foo.bar() vs foo.bar();

node

protected SimpleNode node

The resulting AST we can call value() on

Constructor Detail

ExpressionImpl

ExpressionImpl(java.lang.String expr,
               SimpleNode ref)

do not let this be generally instantiated with a 'new'

Method Detail

evaluate

public java.lang.Object evaluate(JexlContext context)
                          throws java.lang.Exception

Evaluate the expression and return the value. Before JEXL evaluates the expression, any pre-resolvers will be called. If the pre-resolver provides a value, it is returned. If JEXL evaluates the expression as null, post-resolvers are called and any resulting value returned.

Specified by:

evaluate in interface Expression

Parameters:

context - Context containing objects/data used for evaluation

Returns:

value of expression

Throws:

java.lang.Exception

tryResolver

protected java.lang.Object tryResolver(java.util.List resolverList,
                                       JexlContext context)

Tries the resolvers in the given resolverlist against the context

Parameters:

resolverList - list of JexlExprResolvers

context - JexlContext to use for evauluation

Returns:

value (including null) or JexlExprResolver.NO_VALUE

getExpression

public java.lang.String getExpression()

returns original expression string

Specified by:

getExpression in interface Expression

Returns:

The JEXL expression to be evaluated

addPreResolver

public void addPreResolver(JexlExprResolver resolver)

Description copied from interface: Expression

allows addition of a resolver to allow custom interdiction of expression evaluation

Specified by:

addPreResolver in interface Expression

Parameters:

resolver - resolver to be called before Jexl expression evaluated

addPostResolver

public void addPostResolver(JexlExprResolver resolver)

allows addition of a resolver to allow custom interdiction of expression evaluation

Specified by:

addPostResolver in interface Expression

Parameters:

resolver - resolver to be called if Jexl expression evaluated to null