001/*
002 * Shredzone Commons
003 *
004 * Copyright (C) 2012 Richard "Shred" Körber
005 *   http://commons.shredzone.org
006 *
007 * This program is free software: you can redistribute it and/or modify
008 * it under the terms of the GNU Library General Public License as
009 * published by the Free Software Foundation, either version 3 of the
010 * License, or (at your option) any later version.
011 *
012 * This program is distributed in the hope that it will be useful,
013 * but WITHOUT ANY WARRANTY; without even the implied warranty of
014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
015 * GNU General Public License for more details.
016 *
017 * You should have received a copy of the GNU Library General Public License
018 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
019 */
020
021package org.shredzone.commons.view.annotation;
022
023import java.lang.annotation.Documented;
024import java.lang.annotation.ElementType;
025import java.lang.annotation.Retention;
026import java.lang.annotation.RetentionPolicy;
027import java.lang.annotation.Target;
028
029import org.shredzone.commons.view.exception.PageNotFoundException;
030
031/**
032 * If a view handler parameter is annotated with {@link Optional}, it also accepts
033 * {@code null} if there is no matching parameter value. Otherwise, a missing parameter
034 * value leads to a {@link PageNotFoundException}.
035 *
036 * @author Richard "Shred" Körber
037 */
038@Target(ElementType.PARAMETER)
039@Retention(RetentionPolicy.RUNTIME)
040@Documented
041public @interface Optional {
042
043}