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    package org.apache.commons.jxpath.servlet;
018    
019    import org.apache.commons.jxpath.Variables;
020    
021    /**
022     * Implementation of the Variables interface that provides access
023     * to a single object using a reserved name (keyword).
024     *
025     * @author Dmitri Plotnikov
026     * @version $Revision: 652925 $ $Date: 2008-05-02 17:05:41 -0500 (Fri, 02 May 2008) $
027     */
028    public class KeywordVariables implements Variables {
029        private static final long serialVersionUID = 894145608741325442L;
030    
031        private String keyword;
032        private Object object;
033    
034        /**
035         * Create a new KeywordVariables.
036         * @param keyword String
037         * @param object value
038         */
039        public KeywordVariables(String keyword, Object object) {
040            if (keyword == null) {
041                throw new IllegalArgumentException("keyword cannot be null");
042            }
043            this.keyword = keyword;
044            this.object = object;
045        }
046    
047        public boolean isDeclaredVariable(String variable) {
048            return variable.equals(keyword);
049        }
050    
051        public Object getVariable(String variable) {
052            return isDeclaredVariable(variable) ? object : null;
053        }
054    
055        public void declareVariable(String variable, Object value) {
056            throw new UnsupportedOperationException(
057                "Cannot declare new keyword variables.");
058        }
059    
060        public void undeclareVariable(String variable) {
061            throw new UnsupportedOperationException(
062                "Cannot undeclare keyword variables.");
063        }
064    }