/*
 * 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,
 * 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.apache.openjpa.persistence.graph;

import java.io.Serializable;

import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.MappedSuperclass;

/**
 * Persistent Graph is a marker for persistent version of a {@link Graph}.
 * <br>
 * A persistent graph does not declare how the persistent state of the graph is captured and hence is abstract.
 * But Persistent Graph is unique to be persistent in a JPA sense, because JPA does <em>not</em> represent 
 * container instances such as {@link java.util.Set} or {@link java.util.List} as <em>first class</em> type --
 * i.e. their instances do not carry a persistent identity. But declaring a graph as persistent type amounts
 * to represent the graph as a first class persistent type with its own persistent identity.  
 * <br>
 * Persistent Graph defines a auto-generated persistent identity.
 * 
 * @author Pinaki Poddar
 *
 * @param <E> type of element.
 */
@SuppressWarnings("serial")
@MappedSuperclass
public abstract class PersistentGraph<E> extends AbstractGraph<E> implements Serializable {
    
    @Id
    @GeneratedValue
    private long id;
    
    public final long getId() {
        return id;
    }
}
