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
018package org.apache.commons.jxpath.servlet;
019
020import org.apache.commons.jxpath.Variables;
021
022/**
023 * Implementation of the Variables interface that provides access to a single object using a reserved name (keyword).
024 */
025public class KeywordVariables implements Variables {
026
027    private static final long serialVersionUID = 894145608741325442L;
028
029    /**
030     * The keyword.
031     */
032    private final String keyword;
033
034    /**
035     * The value.
036     */
037    private final Object value;
038
039    /**
040     * Constructs a new KeywordVariables.
041     *
042     * @param keyword The keyword.
043     * @param value  The value.
044     */
045    public KeywordVariables(final String keyword, final Object value) {
046        if (keyword == null) {
047            throw new IllegalArgumentException("keyword cannot be null");
048        }
049        this.keyword = keyword;
050        this.value = value;
051    }
052
053    @Override
054    public void declareVariable(final String variable, final Object value) {
055        throw new UnsupportedOperationException("Cannot declare new keyword variables.");
056    }
057
058    @Override
059    public Object getVariable(final String variable) {
060        return isDeclaredVariable(variable) ? value : null;
061    }
062
063    @Override
064    public boolean isDeclaredVariable(final String variable) {
065        return variable.equals(keyword);
066    }
067
068    @Override
069    public void undeclareVariable(final String variable) {
070        throw new UnsupportedOperationException("Cannot undeclare keyword variables.");
071    }
072}