javax.servlet.jsp.el
Class Expression

java.lang.Object
  javax.servlet.jsp.el.Expression

public abstract class Expression
extends Object

The abstract class for a prepared expression.

An instance of an Expression can be obtained via from an ExpressionEvaluator instance.

An Expression may or not have done a syntactic parse of the expression. A client invoking the evaluate() method should be ready for the case where ELParseException exceptions are raised.

Since:

2.0

Constructor Summary

Expression()

Method Summary

abstract Object

evaluate(VariableResolver vResolver) Evaluates an expression that was previously prepared.

Methods inherited from class java.lang.Object

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

Constructor Detail

Expression

public Expression()

Method Detail

evaluate

public abstract Object evaluate(VariableResolver vResolver)
                         throws ELException

Evaluates an expression that was previously prepared. In some implementations preparing an expression involves full syntactic validation, but others may not do so. Evaluating the expression may raise an ELParseException as well as other ELExceptions due to run-time evaluation.

Parameters:

vResolver - A VariableResolver instance that can be used at runtime to resolve the name of implicit objects into Objects.

Returns:

The result of the expression evaluation.

Throws:

ELException - Thrown if the expression evaluation failed.