# Identity.java

    /*
     * Copyright (c) 2007, Rickard Öberg. All Rights Reserved.
     * Copyright (c) 2007, Niclas Hedhman. All Rights Reserved.
     *
     * Licensed 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, software
     * distributed under the License is distributed on an "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.
     *
     */
    package org.qi4j.api.entity;

    import org.qi4j.api.injection.scope.State;
    import org.qi4j.api.mixin.Mixins;
    import org.qi4j.api.property.Immutable;
    import org.qi4j.api.property.Property;

    /**
     * This interface provides the identity of the object which may be used
     * to store the state in a database. It is not the responsibility of the
     * framework to come up with a good identity string.
     */
    @Mixins( Identity.IdentityMixin.class )
    public interface Identity
    {
        /**
         * Returns the client view of the identity.
         * <p>
         * It is unique within the owning repository, but potentially not unique globally and between
         * types.
         * </p>
         * @return The Identity of 'this' composite.
         */
        @Immutable
        Property<String> identity();

        /**
         * Default Identity implementation.
         */
        class IdentityMixin
            implements Identity
        {
            @State
            private Property<String> identity;

            @Override
            public Property<String> identity()
            {
                return identity;
            }
        }
    }