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.

Since:

1.0

Version:

$Id: ExpressionImpl.java 397111 2006-04-26 06:47:52Z dion $

Author:

Geir Magnusson Jr.

Field Summary

protected java.lang.String	expression Original expression.
protected SimpleNode	node The resulting AST we can call value() on.
protected java.util.List	postResolvers resolvers called after expression evaluation.
protected java.util.List	preResolvers resolvers called before expression evaluation.

Constructor Summary

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) Evaluates the expression with the variables contained in the supplied JexlContext.
java.lang.String	getExpression() Returns the JEXL expression this Expression was created with.
java.lang.String	toString() Provide a string representation of the expression.
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, wait, wait, wait

Field Detail

preResolvers

protected java.util.List preResolvers

resolvers called before expression evaluation.

postResolvers

protected java.util.List postResolvers

resolvers called after expression evaluation.

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'.

Parameters:

expr - the expression.

ref - the parsed expression.

Method Detail

evaluate

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

Evaluates the expression with the variables contained in the supplied JexlContext.

Specified by:

evaluate in interface Expression

Parameters:

context - A JexlContext containing variables.

Returns:

The result of this evaluation

Throws:

java.lang.Exception - on any error

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 the JEXL expression this Expression was created with.

Specified by:

getExpression in interface Expression

Returns:

The JEXL expression to be evaluated

addPreResolver

public void addPreResolver(JexlExprResolver resolver)

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.

toString

public java.lang.String toString()

Provide a string representation of the expression.

Overrides:

toString in class java.lang.Object

Returns:

the expression or blank if it's null.