ImmutableFacet.java

/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you 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,
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 *  "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.
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package org.apache.isis.core.metamodel.facets.object.immutable;

import org.apache.isis.applib.annotation.When;
import org.apache.isis.core.metamodel.facetapi.FacetHolder;
import org.apache.isis.core.metamodel.facets.WhenValueFacet;
import org.apache.isis.core.metamodel.facets.object.value.EqualByContentFacet;
import org.apache.isis.core.metamodel.facets.object.value.ValueFacet;
import org.apache.isis.core.metamodel.interactions.DisablingInteractionAdvisor;
import org.apache.isis.core.metamodel.spec.ObjectSpecification;
import org.apache.isis.core.metamodel.spec.feature.ObjectMember;

/**
 * Indicates that the instances of this class are immutable and so may not be
 * modified either through the viewer or indeed programmatically.
 * 
 * <p>
 * In the standard Apache Isis Programming Model, typically corresponds to
 * applying the <tt>@Immutable</tt> annotation at the class level.
 * 
 * @see EqualByContentFacet
 * @see ValueFacet
 */
public interface ImmutableFacet extends WhenValueFacet, DisablingInteractionAdvisor {

    /**
     * Clone this facet onto another {@link FacetHolder}.
     * 
     * <p>
     * Introduced to allow this facet to be installed onto the
     * {@link ObjectSpecification}, and then copied down onto each of the spec's
     * {@link ObjectMember}s.
     */
    void copyOnto(FacetHolder holder);

    public final static class Utils {

        private Utils(){}
        public static boolean isAlwaysImmutable(final ObjectSpecification specification) {
            // this is a workaround for a dubious test
            if (specification == null) {
                return false;
            }

            final ImmutableFacet immutableFacet = specification.getFacet(ImmutableFacet.class);
            if (immutableFacet == null) {
                return false;
            }
            return immutableFacet.when() == When.ALWAYS;
        }

        public static boolean isImmutableOncePersisted(final ObjectSpecification specification) {
            // this is a workaround for a dubious test
            if (specification == null) {
                return false;
            }

            final ImmutableFacet immutableFacet = specification.getFacet(ImmutableFacet.class);
            if (immutableFacet == null) {
                return false;
            }
            return immutableFacet.when() == When.ONCE_PERSISTED;
        }

    }
}