    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    }