001    /*
002    * Licensed to the Apache Software Foundation (ASF) under one or more
003    * contributor license agreements.  See the NOTICE file distributed with
004    * this work for additional information regarding copyright ownership.
005    * The ASF licenses this file to You under the Apache License, Version 2.0
006    * (the "License"); you may not use this file except in compliance with
007    * the License.  You may obtain a copy of the License at
008    *
009    *     http://www.apache.org/licenses/LICENSE-2.0
010    *
011    * Unless required by applicable law or agreed to in writing, software
012    * distributed under the License is distributed on an "AS IS" BASIS,
013    * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014    * See the License for the specific language governing permissions and
015    * limitations under the License.
016    */
017    
018    
019    package javax.servlet.jsp.el;
020    
021    
022    /**
023     * <p>The abstract class for a prepared expression.</p>
024     *
025     * <p>An instance of an Expression can be obtained via from an 
026     * ExpressionEvaluator instance.</p>
027     *
028     * <p>An Expression may or not have done a syntactic parse of the expression.
029     * A client invoking the evaluate() method should be ready for the case 
030     * where ELParseException exceptions are raised. </p>
031     *
032     * @since 2.0
033     * @deprecated
034     */
035    public abstract class Expression {
036    
037        /** 
038         * Evaluates an expression that was previously prepared.  In some 
039         * implementations preparing an expression involves full syntactic 
040         * validation, but others may not do so.  Evaluating the expression may 
041         * raise an ELParseException as well as other ELExceptions due to 
042         * run-time evaluation.
043         *
044         * @param vResolver A VariableResolver instance that can be used at 
045         *   runtime to resolve the name of implicit objects into Objects.
046         * @return The result of the expression evaluation.
047         *
048         * @exception ELException Thrown if the expression evaluation failed.
049         */ 
050        public abstract Object evaluate( VariableResolver vResolver )
051            throws ELException;
052    }
053