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.betwixt.expression;
018    
019    /** <p><code>StringExpression</code> returns the current context object as a string.</p>
020      *
021      * @author <a href="mailto:jstrachan@apache.org">James Strachan</a>
022      * @version $Revision: 438373 $
023      */
024    public class StringExpression implements Expression {
025        
026        /** We only need only <code>StringExpression</code> */
027        private static final StringExpression singleton = new StringExpression();
028        
029        /** 
030         * Gets the singleton 
031         * @return the singleton <code>StringExpression</code> instance
032         */
033        public static StringExpression getInstance() {
034            return singleton;
035        }
036        
037        /** Base constructor. Should this be private? */
038        public StringExpression() {
039        }
040        
041        /** Return the context bean as a string
042          *
043          * @param context evaluate expression against this context
044          * @return the <code>toString()</code> representation of the context bean
045          */
046        public Object evaluate(Context context) {
047            Object value = context.getBean();
048            if ( value != null ) {
049                return value.toString();
050            }
051            return null;
052        }
053        
054        /**
055         * Do nothing 
056         * @see org.apache.commons.betwixt.expression.Expression
057         */
058        public void update(Context context, String newValue) {
059            // do nothing
060        }
061        
062        /**
063         * Returns something useful for logging.
064         * @return the (short) class name
065         */
066        public String toString() {
067            return "StringExpression";
068        }
069    
070    }