JavaServer Pages, 3rd Edition

Name

ExpressionEvaluator

Synopsis

The ExpressionEvaluator is the main class for the EL machinery, providing methods for preparation and evaluation of a single EL expression. In a JSP environment, an instance of this class can be obtained from the JspContext.

Synopsis

Class name:	javax.servlet.jsp.el.ExpressionEvaluator
Extends:	None
Implements:	None
Implemented by:	Internal container-dependent class; most containers use the reference implementation of the class (developed in the Apache Jakarta project)

Constructors

public ExpressionEvaluator( )

Creates a new ExpressionEvaluator instance.

Methods

public abstract Object evaluate(String expression, Class expectedType, VariableResolver variableResolver, FunctionMapper functionMapper) throws ELException

Evaluates the expression (a String starting with ${ and ending with }) using the variables provided by the VariableResolver and the functions provided by the FunctionMapper. The evaluation result is coerced to the specified expected type according to the rules described in Appendix C and returned.

public abstract Object parseExpression(String expression, Class expectedType, FunctionMapper functionMapper) throws ELException

Prepares the expression (a String starting with ${ and ending with }) for later evaluation. The method typically performs syntactic validation and throws an ELParseException if an error is found.