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.collection; 018 019 import java.util.Collection; 020 import java.util.Iterator; 021 022 import org.apache.commons.collections.Predicate; 023 024 /** 025 * Decorates another <code>Collection</code> to validate that additions 026 * match a specified predicate. 027 * <p> 028 * This collection exists to provide validation for the decorated collection. 029 * It is normally created to decorate an empty collection. 030 * If an object cannot be added to the collection, an IllegalArgumentException is thrown. 031 * <p> 032 * One usage would be to ensure that no null entries are added to the collection. 033 * <pre>Collection coll = PredicatedCollection.decorate(new ArrayList(), NotNullPredicate.INSTANCE);</pre> 034 * <p> 035 * This class is Serializable from Commons Collections 3.1. 036 * 037 * @since Commons Collections 3.0 038 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $ 039 * 040 * @author Stephen Colebourne 041 * @author Paul Jack 042 */ 043 public class PredicatedCollection extends AbstractSerializableCollectionDecorator { 044 045 /** Serialization version */ 046 private static final long serialVersionUID = -5259182142076705162L; 047 048 /** The predicate to use */ 049 protected final Predicate predicate; 050 051 /** 052 * Factory method to create a predicated (validating) collection. 053 * <p> 054 * If there are any elements already in the collection being decorated, they 055 * are validated. 056 * 057 * @param coll the collection to decorate, must not be null 058 * @param predicate the predicate to use for validation, must not be null 059 * @return a new predicated collection 060 * @throws IllegalArgumentException if collection or predicate is null 061 * @throws IllegalArgumentException if the collection contains invalid elements 062 */ 063 public static Collection decorate(Collection coll, Predicate predicate) { 064 return new PredicatedCollection(coll, predicate); 065 } 066 067 //----------------------------------------------------------------------- 068 /** 069 * Constructor that wraps (not copies). 070 * <p> 071 * If there are any elements already in the collection being decorated, they 072 * are validated. 073 * 074 * @param coll the collection to decorate, must not be null 075 * @param predicate the predicate to use for validation, must not be null 076 * @throws IllegalArgumentException if collection or predicate is null 077 * @throws IllegalArgumentException if the collection contains invalid elements 078 */ 079 protected PredicatedCollection(Collection coll, Predicate predicate) { 080 super(coll); 081 if (predicate == null) { 082 throw new IllegalArgumentException("Predicate must not be null"); 083 } 084 this.predicate = predicate; 085 for (Iterator it = coll.iterator(); it.hasNext(); ) { 086 validate(it.next()); 087 } 088 } 089 090 /** 091 * Validates the object being added to ensure it matches the predicate. 092 * <p> 093 * The predicate itself should not throw an exception, but return false to 094 * indicate that the object cannot be added. 095 * 096 * @param object the object being added 097 * @throws IllegalArgumentException if the add is invalid 098 */ 099 protected void validate(Object object) { 100 if (predicate.evaluate(object) == false) { 101 throw new IllegalArgumentException("Cannot add Object '" + object + "' - Predicate rejected it"); 102 } 103 } 104 105 //----------------------------------------------------------------------- 106 /** 107 * Override to validate the object being added to ensure it matches 108 * the predicate. 109 * 110 * @param object the object being added 111 * @return the result of adding to the underlying collection 112 * @throws IllegalArgumentException if the add is invalid 113 */ 114 public boolean add(Object object) { 115 validate(object); 116 return getCollection().add(object); 117 } 118 119 /** 120 * Override to validate the objects being added to ensure they match 121 * the predicate. If any one fails, no update is made to the underlying 122 * collection. 123 * 124 * @param coll the collection being added 125 * @return the result of adding to the underlying collection 126 * @throws IllegalArgumentException if the add is invalid 127 */ 128 public boolean addAll(Collection coll) { 129 for (Iterator it = coll.iterator(); it.hasNext(); ) { 130 validate(it.next()); 131 } 132 return getCollection().addAll(coll); 133 } 134 135 }