001/*
002 *  Licensed to the Apache Software Foundation (ASF) under one
003 *  or more contributor license agreements.  See the NOTICE file
004 *  distributed with this work for additional information
005 *  regarding copyright ownership.  The ASF licenses this file
006 *  to you under the Apache License, Version 2.0 (the
007 *  "License"); you may not use this file except in compliance
008 *  with the License.  You may obtain a copy of the License at
009 *
010 *        http://www.apache.org/licenses/LICENSE-2.0
011 *
012 *  Unless required by applicable law or agreed to in writing,
013 *  software distributed under the License is distributed on an
014 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
015 *  KIND, either express or implied.  See the License for the
016 *  specific language governing permissions and limitations
017 *  under the License.
018 */
019
020package org.apache.isis.core.progmodel.facets.object.validate;
021
022import org.apache.isis.core.metamodel.adapter.ObjectAdapter;
023import org.apache.isis.core.metamodel.facetapi.Facet;
024import org.apache.isis.core.metamodel.facets.object.callbacks.PersistingCallbackFacet;
025import org.apache.isis.core.metamodel.facets.object.callbacks.UpdatingCallbackFacet;
026import org.apache.isis.core.metamodel.interactions.ValidatingInteractionAdvisor;
027
028/**
029 * Mechanism for determining whether this object is in a valid state, for
030 * example so that it can be persisted or updated.
031 * 
032 * <p>
033 * Even though all the properties of an object may themselves be valid, there
034 * could be inter-property dependencies which are invalid. For example
035 * <tt>fromDate</tt> > <tt>toDate</tt> would probably represent an invalid
036 * state.
037 * 
038 * <p>
039 * In the standard Apache Isis Programming Model, typically corresponds to the
040 * <tt>validate</tt> method.
041 * 
042 * @see PersistingCallbackFacet
043 * @see UpdatingCallbackFacet
044 */
045public interface ValidateObjectFacet extends Facet, ValidatingInteractionAdvisor {
046
047    /**
048     * The reason the object is invalid.
049     * 
050     * <p>
051     * . If the object is actually valid, should return <tt>null</tt>.
052     */
053    public String invalidReason(ObjectAdapter adapter);
054
055}