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/*
* 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
 */
@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.
     *
     * @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;
}