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 */
017package org.apache.wicket.validation;
018
019import org.apache.wicket.markup.html.form.FormComponent;
020
021/**
022 * Marker interface for validators that will accept a <code>null</code> value. Without implementing
023 * this interface Wicket will never pass <code>null</code> values to
024 * {@link IValidator#validate(IValidatable)}.
025 * <p>
026 * Keep in mind that the {@link FormComponent} must have set the required property to
027 * <code>false</code>, otherwise Wicket will not permit the validator to process the
028 * <code>null</code> value.
029 * 
030 * @author Matej Knopp
031 * @param <T>
032 *            type of validatable
033 * @since 1.2.6
034 * @see IValidator
035 * @see FormComponent#setRequired(boolean)
036 */
037public interface INullAcceptingValidator<T> extends IValidator<T>
038{
039
040}