001/*
002 * (C) Copyright 2014 Nuxeo SA (http://nuxeo.com/) and contributors.
003 *
004 * All rights reserved. This program and the accompanying materials
005 * are made available under the terms of the GNU Lesser General Public License
006 * (LGPL) version 2.1 which accompanies this distribution, and is available at
007 * http://www.gnu.org/licenses/lgpl-2.1.html
008 *
009 * This library is distributed in the hope that it will be useful,
010 * but WITHOUT ANY WARRANTY; without even the implied warranty of
011 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
012 * Lesser General Public License for more details.
013 *
014 * Contributors:
015 *     Nicolas Chapurlat <nchapurlat@nuxeo.com>
016 */
017
018package org.nuxeo.ecm.core.schema.types.constraints;
019
020import java.io.Serializable;
021import java.util.HashMap;
022import java.util.Map;
023
024/**
025 * This constraint ensure some object is not null.
026 * <p>
027 * This class is a singleton. Use {@link #get()} to get the singleton.
028 * </p>
029 *
030 * @since 7.1
031 * @author <a href="mailto:nc@nuxeo.com">Nicolas Chapurlat</a>
032 */
033public class NotNullConstraint extends AbstractConstraint {
034
035    private static final long serialVersionUID = 1L;
036
037    private static final String NAME = "NotNullConstraint";
038
039    // Lazy ang thread safe singleton instance.
040    private static class Holder {
041        private static final NotNullConstraint INSTANCE = new NotNullConstraint();
042    }
043
044    private NotNullConstraint() {
045    }
046
047    public static NotNullConstraint get() {
048        return Holder.INSTANCE;
049    }
050
051    @Override
052    public boolean validate(Object object) {
053        return object != null;
054    }
055
056    /**
057     * Here, value is : <br>
058     * name = {@value #NAME}. <br>
059     * parameters is empty
060     */
061    @Override
062    public Description getDescription() {
063        Map<String, Serializable> params = new HashMap<String, Serializable>();
064        return new Description(NotNullConstraint.NAME, params);
065    }
066
067    @Override
068    public int hashCode() {
069        return NotNullConstraint.class.hashCode();
070    }
071
072    @Override
073    public boolean equals(Object obj) {
074        return obj != null && obj instanceof NotNullConstraint;
075    }
076}