/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements.  See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License.  You may obtain a copy of the License at
*
*     http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/


package javax.servlet.jsp.el;


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
Deprecated:
As of JSP 2.1, replaced by javax.el.ValueExpression/**
 * <p>The abstract class for a prepared expression.</p>
 *
 * <p>An instance of an Expression can be obtained via from an
 * ExpressionEvaluator instance.</p>
 *
 * <p>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. </p>
 *
 * @since 2.0
 * @deprecated As of JSP 2.1, replaced by javax.el.ValueExpression
 */
@SuppressWarnings("dep-ann") // TCK signature test fails with annotation
public abstract class Expression {

    
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.
Params:
vResolver – A VariableResolver instance that can be used at
  runtime to resolve the name of implicit objects into Objects.
Throws:
ELException – Thrown if the expression evaluation failed.
Returns:
The result of the expression evaluation./**
     * 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.
     *
     * @param vResolver A VariableResolver instance that can be used at
     *   runtime to resolve the name of implicit objects into Objects.
     * @return The result of the expression evaluation.
     *
     * @exception ELException Thrown if the expression evaluation failed.
     */
    public abstract Object evaluate( VariableResolver vResolver )
        throws ELException;
}