Java tutorial
/* * Copyright 2003-2004 The Apache Software Foundation * * Licensed 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</code> 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);</pre> * <p> * This class is Serializable from Commons Collections 3.1. * * @since Commons Collections 3.0 * @version $Revision: 1.14 $ $Date: 2004/06/07 22:14:42 $ * * @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</code>. * * @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); } }