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;
018    
019    import java.util.HashMap;
020    
021    /**
022     * A basic implementation of the Variables interface that uses a HashMap.
023     *
024     * @author Dmitri Plotnikov
025     * @version $Revision: 652925 $ $Date: 2008-05-02 17:05:41 -0500 (Fri, 02 May 2008) $
026     */
027    public class BasicVariables implements Variables {
028        private static final long serialVersionUID = 2708263960832062725L;
029    
030        /**
031         * Contains the values of declared variables
032         */
033        private HashMap vars = new HashMap();
034    
035        /**
036         * Returns true if the variable has been defined, even if the
037         * value of the variable is null.
038         *
039         * @param varName is a variable name without the "$" sign
040         *
041         * @return true if the variable is declared
042         */
043        public boolean isDeclaredVariable(String varName) {
044            return vars.containsKey(varName);
045        }
046    
047        /**
048         * Returns the value of the variable if it is defined,
049         * otherwise, throws IllegalArgumentException
050         *
051         * @param varName is a variable name without the "$" sign
052         *
053         * @return the value of the variable
054         */
055        public Object getVariable(String varName) {
056            // Note that a variable may be defined with a null value
057    
058            if (vars.containsKey(varName)) {
059                return vars.get(varName);
060            }
061    
062            throw new IllegalArgumentException(
063                "No such variable: '" + varName + "'");
064        }
065    
066        /**
067         * Defines a new variable with the specified value or modifies
068         * the value of an existing variable.
069         *
070         * @param varName is a variable name without the "$" sign
071         * @param value is the new value for the variable, which can be null
072         */
073        public void declareVariable(String varName, Object value) {
074            vars.put(varName, value);
075        }
076    
077        /**
078         * Removes an existing variable. May throw UnsupportedOperationException.
079         *
080         * @param varName is a variable name without the "$" sign
081         */
082        public void undeclareVariable(String varName) {
083            vars.remove(varName);
084        }
085    
086        public String toString() {
087            return vars.toString();
088        }
089    }