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    }