org.apache.taglibs.standard.lang.support.ExpressionEvaluator Maven / Gradle / Ivy
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* of the Common Development and Distribution License
* (the "License"). You may not use this file except
* in compliance with the License.
*
* You can obtain a copy of the license at
* glassfish/bootstrap/legal/CDDLv1.0.txt or
* https://glassfish.dev.java.net/public/CDDLv1.0.html.
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* glassfish/bootstrap/legal/CDDLv1.0.txt. If applicable,
* add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your
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* Copyright 2005 Sun Microsystems, Inc. All rights reserved.
*
* Portions Copyright Apache Software Foundation.
*/
package org.apache.taglibs.standard.lang.support;
import javax.servlet.jsp.JspException;
import javax.servlet.jsp.PageContext;
import javax.servlet.jsp.tagext.Tag;
/**
* The interface for an expression-language validator and evaluator.
* Classes that implement an expression language expose their functionality
* via this interface.
*
* The validate() and evaluate() methods must be thread-safe. That is,
* multiple threads may call these methods on the same ExpressionEvaluator
* object simultaneously. Implementations should synchronize access if
* they depend on transient state. Implementations should not, however,
* assume that only one object of each ExpressionEvaluator type will be
* instantiated; global caching should therefore be static. No release()
* mechanism or robust lifecycle is specified, for language-interpreter
* pluggability is experimental in EA2.
*
* WARNING: This class supports experimentation for the EA2
* release of JSTL; it is not expected to be part of the final RI or
* specification.
*
* @author Shawn Bayern (based exactly on rev1 draft)
*/
public interface ExpressionEvaluator {
/**
* Translation time validation of an expression.
* This method will return a null String if the expression
* is valid; otherwise an error message.
*/
public String validate(String attributeName,
String expression);
/**
* Evaluates the expression at request time.
*/
public Object evaluate(String attributeName,
String expression,
Class expectedType,
Tag tag,
PageContext pageContext)
throws JspException;
}