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.collections.functors;
018
019 import java.io.Serializable;
020
021 import org.apache.commons.collections.FunctorException;
022 import org.apache.commons.collections.Predicate;
023 import org.apache.commons.collections.Transformer;
024
025 /**
026 * Predicate implementation that returns the result of a transformer.
027 *
028 * @since Commons Collections 3.0
029 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
030 *
031 * @author Stephen Colebourne
032 */
033 public final class TransformerPredicate implements Predicate, Serializable {
034
035 /** Serial version UID */
036 private static final long serialVersionUID = -2407966402920578741L;
037
038 /** The transformer to call */
039 private final Transformer iTransformer;
040
041 /**
042 * Factory to create the predicate.
043 *
044 * @param transformer the transformer to decorate
045 * @return the predicate
046 * @throws IllegalArgumentException if the transformer is null
047 */
048 public static Predicate getInstance(Transformer transformer) {
049 if (transformer == null) {
050 throw new IllegalArgumentException("The transformer to call must not be null");
051 }
052 return new TransformerPredicate(transformer);
053 }
054
055 /**
056 * Constructor that performs no validation.
057 * Use <code>getInstance</code> if you want that.
058 *
059 * @param transformer the transformer to decorate
060 */
061 public TransformerPredicate(Transformer transformer) {
062 super();
063 iTransformer = transformer;
064 }
065
066 /**
067 * Evaluates the predicate returning the result of the decorated transformer.
068 *
069 * @param object the input object
070 * @return true if decorated transformer returns Boolean.TRUE
071 * @throws FunctorException if the transformer returns an invalid type
072 */
073 public boolean evaluate(Object object) {
074 Object result = iTransformer.transform(object);
075 if (result instanceof Boolean == false) {
076 throw new FunctorException(
077 "Transformer must return an instanceof Boolean, it was a "
078 + (result == null ? "null object" : result.getClass().getName()));
079 }
080 return ((Boolean) result).booleanValue();
081 }
082
083 /**
084 * Gets the transformer.
085 *
086 * @return the transformer
087 * @since Commons Collections 3.1
088 */
089 public Transformer getTransformer() {
090 return iTransformer;
091 }
092
093 }