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Commons Collections example source code file (PredicatedMap.java)

This example Commons Collections source code file (PredicatedMap.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Commons Collections tags/keywords

abstractinputcheckedmapdecorator, cannot, cannot, illegalargumentexception, illegalargumentexception, io, ioexception, iterator, map, object, object, predicate, predicate, predicatedmap, serializable, util

The Commons Collections PredicatedMap.java source code

/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */
package org.apache.commons.collections.map;

import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.Serializable;
import java.util.Iterator;
import java.util.Map;

import org.apache.commons.collections.Predicate;

/**
 * Decorates another <code>Map to validate that additions
 * match a specified predicate.
 * <p>
 * This map exists to provide validation for the decorated map.
 * It is normally created to decorate an empty map.
 * If an object cannot be added to the map, an IllegalArgumentException is thrown.
 * <p>
 * One usage would be to ensure that no null keys are added to the map.
 * <pre>Map map = PredicatedSet.decorate(new HashMap(), NotNullPredicate.INSTANCE, null);
* <p> * <strong>Note that PredicatedMap is not synchronized and is not thread-safe. * If you wish to use this map from multiple threads concurrently, you must use * appropriate synchronization. The simplest approach is to wrap this map * using {@link java.util.Collections#synchronizedMap(Map)}. This class may throw * exceptions when accessed by concurrent threads without synchronization. * <p> * This class is Serializable from Commons Collections 3.1. * * @since Commons Collections 3.0 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $ * * @author Stephen Colebourne * @author Paul Jack */ public class PredicatedMap extends AbstractInputCheckedMapDecorator implements Serializable { /** Serialization version */ private static final long serialVersionUID = 7412622456128415156L; /** The key predicate to use */ protected final Predicate keyPredicate; /** The value predicate to use */ protected final Predicate valuePredicate; /** * Factory method to create a predicated (validating) map. * <p> * If there are any elements already in the list being decorated, they * are validated. * * @param map the map to decorate, must not be null * @param keyPredicate the predicate to validate the keys, null means no check * @param valuePredicate the predicate to validate to values, null means no check * @throws IllegalArgumentException if the map is null */ public static Map decorate(Map map, Predicate keyPredicate, Predicate valuePredicate) { return new PredicatedMap(map, keyPredicate, valuePredicate); } //----------------------------------------------------------------------- /** * Constructor that wraps (not copies). * * @param map the map to decorate, must not be null * @param keyPredicate the predicate to validate the keys, null means no check * @param valuePredicate the predicate to validate to values, null means no check * @throws IllegalArgumentException if the map is null */ protected PredicatedMap(Map map, Predicate keyPredicate, Predicate valuePredicate) { super(map); this.keyPredicate = keyPredicate; this.valuePredicate = valuePredicate; Iterator it = map.entrySet().iterator(); while (it.hasNext()) { Map.Entry entry = (Map.Entry) it.next(); Object key = entry.getKey(); Object value = entry.getValue(); validate(key, value); } } //----------------------------------------------------------------------- /** * Write the map out using a custom routine. * * @param out the output stream * @throws IOException * @since Commons Collections 3.1 */ private void writeObject(ObjectOutputStream out) throws IOException { out.defaultWriteObject(); out.writeObject(map); } /** * Read the map in using a custom routine. * * @param in the input stream * @throws IOException * @throws ClassNotFoundException * @since Commons Collections 3.1 */ private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException { in.defaultReadObject(); map = (Map) in.readObject(); } //----------------------------------------------------------------------- /** * Validates a key value pair. * * @param key the key to validate * @param value the value to validate * @throws IllegalArgumentException if invalid */ protected void validate(Object key, Object value) { if (keyPredicate != null && keyPredicate.evaluate(key) == false) { throw new IllegalArgumentException("Cannot add key - Predicate rejected it"); } if (valuePredicate != null && valuePredicate.evaluate(value) == false) { throw new IllegalArgumentException("Cannot add value - Predicate rejected it"); } } /** * Override to validate an object set into the map via <code>setValue. * * @param value the value to validate * @throws IllegalArgumentException if invalid * @since Commons Collections 3.1 */ protected Object checkSetValue(Object value) { if (valuePredicate.evaluate(value) == false) { throw new IllegalArgumentException("Cannot set value - Predicate rejected it"); } return value; } /** * Override to only return true when there is a value transformer. * * @return true if a value predicate is in use * @since Commons Collections 3.1 */ protected boolean isSetValueChecking() { return (valuePredicate != null); } //----------------------------------------------------------------------- public Object put(Object key, Object value) { validate(key, value); return map.put(key, value); } public void putAll(Map mapToCopy) { Iterator it = mapToCopy.entrySet().iterator(); while (it.hasNext()) { Map.Entry entry = (Map.Entry) it.next(); Object key = entry.getKey(); Object value = entry.getValue(); validate(key, value); } map.putAll(mapToCopy); } }

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