org.apache.commons.jelly.expression

Interface Expression

All Known Implementing Classes:

CompositeExpression, ConstantExpression, EscapingExpression, ExpressionSupport, JexlExpression, XPathExpression

public interface Expression

Expression represents an arbitrary expression using some pluggable expression language.

Version:

$Revision: 155420 $

Author:

James Strachan

Field Summary

Fields

Modifier and Type	Field and Description
static Expression	NULL Singleton instance that represents the expression that evaluates to null.

Method Summary

Methods

Modifier and Type	Method and Description
Object	evaluate(JellyContext context) Evaluates the expression with the given context and returns the result
boolean	evaluateAsBoolean(JellyContext context) Evaluates the expression with the given context coercing the result to be a boolean.
Iterator	evaluateAsIterator(JellyContext context) Evaluates the expression with the given context coercing the result to be an Iterator.
String	evaluateAsString(JellyContext context) Evaluates the expression with the given context coercing the result to be a String.
Object	evaluateRecurse(JellyContext context) This method evaluates the expression until a value (a non-Expression) object is returned.
String	getExpressionText()

Field Detail

NULL

static final Expression NULL

Singleton instance that represents the expression that evaluates to null.

Method Detail

getExpressionText

String getExpressionText()

Returns:

the textual representation of this expression

evaluate

Object evaluate(JellyContext context)

Evaluates the expression with the given context and returns the result

evaluateAsString

String evaluateAsString(JellyContext context)

Evaluates the expression with the given context coercing the result to be a String.

evaluateAsBoolean

boolean evaluateAsBoolean(JellyContext context)

Evaluates the expression with the given context coercing the result to be a boolean.

evaluateAsIterator

Iterator evaluateAsIterator(JellyContext context)

Evaluates the expression with the given context coercing the result to be an Iterator.

evaluateRecurse

Object evaluateRecurse(JellyContext context)

This method evaluates the expression until a value (a non-Expression) object is returned. If the expression returns another expression, then the nested expression is evaluated.

Sometimes when Jelly is used inside Maven the value of an expression can actually be another expression. For example if a properties file is read, the values of variables can actually be expressions themselves.

e.g. ${foo.bar} can lookup "foo.bar" in a Maven context which could actually be another expression.

So using this method, nested expressions can be evaluated to the actual underlying value object.