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>EmptyExpression</code> returns the same value as is passed in. </p> 020 * 021 * <p> See {@link #evaluate}. </p> 022 * 023 * @author <a href="mailto:jstrachan@apache.org">James Strachan</a> 024 * @version $Revision: 438373 $ 025 */ 026 public class EmptyExpression implements Expression { 027 028 /** Don't need more than one <code>EmptyExpression</code>*/ 029 private static final EmptyExpression singleton = new EmptyExpression(); 030 031 /** 032 * Gets the singleton instance. 033 * @return the EmptyExpression singleton. 034 */ 035 public static EmptyExpression getInstance() { 036 return singleton; 037 } 038 039 /** Should this be private? 040 */ 041 public EmptyExpression() { 042 } 043 044 /** Return the bean we're evaluating. 045 * @see org.apache.commons.betwixt.expression.Expression 046 */ 047 public Object evaluate(Context context) { 048 return context.getBean(); 049 } 050 051 /** Do nothing 052 * @see org.apache.commons.betwixt.expression.Expression 053 */ 054 public void update(Context context, String newValue) { 055 // do nothing 056 } 057 058 /** 059 * Return something useful for logging. 060 * @return short name for this class 061 */ 062 public String toString() { 063 return "EmptyExpression"; 064 } 065 066 }