1 /* 2 * $Id: AbstractAttributeEvaluator.java 833737 2009-11-07 19:17:09Z apetrelli $ 3 * 4 * Licensed to the Apache Software Foundation (ASF) under one 5 * or more contributor license agreements. See the NOTICE file 6 * distributed with this work for additional information 7 * regarding copyright ownership. The ASF licenses this file 8 * to you under the Apache License, Version 2.0 (the 9 * "License"); you may not use this file except in compliance 10 * with the License. You may obtain a copy of the License at 11 * 12 * http://www.apache.org/licenses/LICENSE-2.0 13 * 14 * Unless required by applicable law or agreed to in writing, 15 * software distributed under the License is distributed on an 16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY 17 * KIND, either express or implied. See the License for the 18 * specific language governing permissions and limitations 19 * under the License. 20 */ 21 package org.apache.tiles.evaluator; 22 23 import org.apache.tiles.Attribute; 24 import org.apache.tiles.Expression; 25 import org.apache.tiles.request.Request; 26 27 /** 28 * Abstract class to link a correct evaluation of an attribute, by evaluating 29 * {@link Attribute#getValue()} and then {@link Attribute#getExpressionObject()}. 30 * 31 * @version $Rev: 833737 $ $Date: 2009-11-08 06:17:09 +1100 (Sun, 08 Nov 2009) $ 32 * @since 2.1.2 33 */ 34 public abstract class AbstractAttributeEvaluator implements AttributeEvaluator { 35 36 /** {@inheritDoc} */ 37 public Object evaluate(Attribute attribute, Request request) { 38 if (attribute == null) { 39 throw new IllegalArgumentException("The attribute cannot be null"); 40 } 41 42 Object retValue = attribute.getValue(); 43 44 if (retValue == null) { 45 Expression expression = attribute.getExpressionObject(); 46 if (expression != null) { 47 retValue = evaluate(attribute.getExpressionObject() 48 .getExpression(), request); 49 } 50 } 51 52 return retValue; 53 } 54 }