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 }