/*
* 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.collection;
import java.util.Collection;
import java.util.Iterator;
import org.apache.commons.collections.Predicate;
/**
* Decorates another <code>Collection</code> to validate that additions
* match a specified predicate.
* <p>
* This collection exists to provide validation for the decorated collection.
* It is normally created to decorate an empty collection.
* If an object cannot be added to the collection, an IllegalArgumentException is thrown.
* <p>
* One usage would be to ensure that no null entries are added to the collection.
* <pre>Collection coll = PredicatedCollection.decorate(new ArrayList(), NotNullPredicate.INSTANCE);</pre>
* <p>
* This class is Serializable from Commons Collections 3.1.
*
* @since Commons Collections 3.0
* @version $Revision: 155406 $ $Date: 2005-02-26 12:55:26 +0000 (Sat, 26 Feb 2005) $
*
* @author Stephen Colebourne
* @author Paul Jack
*/
public class PredicatedCollection extends AbstractSerializableCollectionDecorator {
/** Serialization version */
private static final long serialVersionUID = -5259182142076705162L;
/** The predicate to use */
protected final Predicate predicate;
/**
* Factory method to create a predicated (validating) collection.
* <p>
* If there are any elements already in the collection being decorated, they
* are validated.
*
* @param coll the collection to decorate, must not be null
* @param predicate the predicate to use for validation, must not be null
* @return a new predicated collection
* @throws IllegalArgumentException if collection or predicate is null
* @throws IllegalArgumentException if the collection contains invalid elements
*/
public static Collection decorate(Collection coll, Predicate predicate) {
return new PredicatedCollection(coll, predicate);
}
//-----------------------------------------------------------------------
/**
* Constructor that wraps (not copies).
* <p>
* If there are any elements already in the collection being decorated, they
* are validated.
*
* @param coll the collection to decorate, must not be null
* @param predicate the predicate to use for validation, must not be null
* @throws IllegalArgumentException if collection or predicate is null
* @throws IllegalArgumentException if the collection contains invalid elements
*/
protected PredicatedCollection(Collection coll, Predicate predicate) {
super(coll);
if (predicate == null) {
throw new IllegalArgumentException("Predicate must not be null");
}
this.predicate = predicate;
for (Iterator it = coll.iterator(); it.hasNext(); ) {
validate(it.next());
}
}
/**
* Validates the object being added to ensure it matches the predicate.
* <p>
* The predicate itself should not throw an exception, but return false to
* indicate that the object cannot be added.
*
* @param object the object being added
* @throws IllegalArgumentException if the add is invalid
*/
protected void validate(Object object) {
if (predicate.evaluate(object) == false) {
throw new IllegalArgumentException("Cannot add Object '" + object + "' - Predicate rejected it");
}
}
//-----------------------------------------------------------------------
/**
* Override to validate the object being added to ensure it matches
* the predicate.
*
* @param object the object being added
* @return the result of adding to the underlying collection
* @throws IllegalArgumentException if the add is invalid
*/
public boolean add(Object object) {
validate(object);
return getCollection().add(object);
}
/**
* Override to validate the objects being added to ensure they match
* the predicate. If any one fails, no update is made to the underlying
* collection.
*
* @param coll the collection being added
* @return the result of adding to the underlying collection
* @throws IllegalArgumentException if the add is invalid
*/
public boolean addAll(Collection coll) {
for (Iterator it = coll.iterator(); it.hasNext(); ) {
validate(it.next());
}
return getCollection().addAll(coll);
}
}