/* Copyright 2004, 2005, 2006 Acegi Technology Pty Limited

  *

  * 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.acegisecurity.acls.objectidentity;

 import java.io.Serializable;

 /**

  * Interface representing the identity of an individual domain object instance.

  *

  * <P>

  * As implementations are used as the key for caching and lookup, it is

  * essential that implementations provide methods so that object-equality

  * rather than reference-equality can be relied upon by caches. In other

  * words, a cache can consider two <code>ObjectIdentity</code>s equal if

  * <code>identity1.equals(identity2)</code>, rather than reference-equality of

  * <code>identity1==identity2</code>.

  * </p>

  *

  * @author Ben Alex

  * @version $Id: ObjectIdentity.java 1784 2007-02-24 21:00:24Z luke_t $

  */

 public interface ObjectIdentity extends Serializable {

     //~ Methods ========================================================================================================

     /**

      * Refer to the <code>java.lang.Object</code> documentation for the interface contract.

      *

      * @param obj to be compared

      *

      * @return <code>true</code> if the objects are equal, <code>false</code> otherwise

      */

     boolean equals(Object obj);

     /**

      * Obtains the actual identifier. This identifier must not be reused to represent other domain objects with

      * the same <code>javaType</code>.<p>Because ACLs are largely immutable, it is strongly recommended to use

      * a synthetic identifier (such as a database sequence number for the primary key). Do not use an identifier with

      * business meaning, as that business meaning may change.</p>

      *

      * @return the identifier (unique within this <code>javaType</code>

      */

     Serializable getIdentifier();

     /**

      * Obtains the Java type represented by the domain object.

      *

      * @return the Java type of the domain object

      */

     Class getJavaType();

     /**

      * Refer to the <code>java.lang.Object</code> documentation for the interface contract.

      *

      * @return a hash code representation of this object

      */

     int hashCode();

 }