# ExternalResource.java

    /*
    ** Module   : ExternalResource.java
    ** Abstract : instances of this class represent resources which associate with external
    **            applications.
    **
    ** Copyright (c) 2017-2024, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- ---------------------------------Description----------------------------------
    ** 001 CA  20170228 Created initial version.
    ** 002 IAS 20200922 Get rid of possible NPE on serialization.
    ** 003 CA  20240918 Removed default methods from interfaces and moved them as concrete implementations, as
    **                  default methods cause the Java metaspace to spike one order of magnitude.
    */
    /*
    ** This program is free software: you can redistribute it and/or modify
    ** it under the terms of the GNU Affero General Public License as
    ** published by the Free Software Foundation, either version 3 of the
    ** License, or (at your option) any later version.
    **
    ** This program is distributed in the hope that it will be useful,
    ** but WITHOUT ANY WARRANTY; without even the implied warranty of
    ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    ** GNU Affero General Public License for more details.
    **
    ** You may find a copy of the GNU Affero GPL version 3 at the following
    ** location: https://www.gnu.org/licenses/agpl-3.0.en.html
    **
    ** Additional terms under GNU Affero GPL version 3 section 7:
    **
    **   Under Section 7 of the GNU Affero GPL version 3, the following additional
    **   terms apply to the works covered under the License.  These additional terms
    **   are non-permissive additional terms allowed under Section 7 of the GNU
    **   Affero GPL version 3 and may not be removed by you.
    **
    **   0. Attribution Requirement.
    **
    **     You must preserve all legal notices or author attributions in the covered
    **     work or Appropriate Legal Notices displayed by works containing the covered
    **     work.  You may not remove from the covered work any author or developer
    **     credit already included within the covered work.
    **
    **   1. No License To Use Trademarks.
    **
    **     This license does not grant any license or rights to use the trademarks
    **     Golden Code, FWD, any Golden Code or FWD logo, or any other trademarks
    **     of Golden Code Development Corporation. You are not authorized to use the
    **     name Golden Code, FWD, or the names of any author or contributor, for
    **     publicity purposes without written authorization.
    **
    **   2. No Misrepresentation of Affiliation.
    **
    **     You may not represent yourself as Golden Code Development Corporation or FWD.
    **
    **     You may not represent yourself for publicity purposes as associated with
    **     Golden Code Development Corporation, FWD, or any author or contributor to
    **     the covered work, without written authorization.
    **
    **   3. No Misrepresentation of Source or Origin.
    **
    **     You may not represent the covered work as solely your work.  All modified
    **     versions of the covered work must be marked in a reasonable way to make it
    **     clear that the modified work is not originating from Golden Code Development
    **     Corporation or FWD.  All modified versions must contain the notices of
    **     attribution required in this license.
    */

    package com.goldencode.p2j.util;

    import static com.goldencode.util.NativeTypeSerializer.*;
    import java.io.*;

    /**
     * Instances of this class are helpers to associate a surrogate handle ID with a resource on a
     * remote side.  Useful for i.e. SUBSCRIBE/UNSUBSCRIBE/PUBLISH APIs.
     */
    public class ExternalResource
    implements Deletable,
               WrappedResource,
               Externalizable
    {
       /** The resource ID. */
       private Long id;

       /**
        * Reports if this object is valid for use.
        *
        * @return   Always <code>true</code>.
        */
       @Override
       public boolean valid()
       {
          return true;
       }

       /**
        * Reports if this object is unknown.
        *
        * @return   Always <code>false</code>.
        */
       @Override
       public boolean unknown()
       {
          return false;
       }

       /**
        * Get this resource's ID.
        *
        * @return   See above.
        */
       @Override
       public Long id()
       {
          return id;
       }

       /**
        * Set this resource's ID.
        *
        * @param    id
        *           The resource's ID.
        */
       @Override
       public void id(long id)
       {
          this.id = id;
       }

       /**
        * Perform actual delete of an resource. At the time of this call, it is assumed the resource
        * is valid for deletion (the handle and the resource are both valid).
        */
       @Override
       public void delete()
       {
          ProcedureManager.cleanupSubscriptions(this);

          // the resource was deleted, clean up after it
          handle.removeResource(this);
       }

       /**
        * Check if the resource can veto the delete or not, before attempting the {@link #delete()} call.
        *
        * @param    ref
        *           The exact handle holding the reference, on which the delete is attempted.
        * @param    explicit
        *           Flag indicating this is called via <code>DELETE OBJECT</code> from the application.
        *
        * @return   <code>false</code> if the delete is vetoed.
        */
       @Override
       public boolean allowDelete(handle ref, boolean explicit)
       {
          return true;
       }

       /**
        * Check if this instance equals the given one.
        *
        * @param    obj
        *           The object to check.
        *
        * @return   <code>true</code> if <code>obj</code> is a {@link ExternalResource} and its
        *           {@link #id} is the same as the one in this instance.
        */
       @Override
       public boolean equals(Object obj)
       {
          if (!(obj instanceof ExternalResource))
          {
             return false;
          }

          return ((ExternalResource) obj).id == id;
       }

       /**
        * Compute the hashcode of this instance.
        *
        * @return    {@link Long#hashCode(long)} called on the {@link #id}.
        */
       @Override
       public int hashCode()
       {
          return id == null ? 0 : Long.hashCode(id);
       }

       /**
        * Replacement for the default object writing method. The latest state is written to the output
        * destination.
        *
        * @param    out
        *           The output destination to which fields will be saved.
        *
        * @throws   IOException
        *           In case of I/O errors.
        */
       @Override
       public void writeExternal(ObjectOutput out)
       throws IOException
       {
          writeLong(out, id);
       }

       /**
        * Replacement for the default object reading method. The latest state is read from the input
        * source.
        *
        * @param    in
        *           The input source from which fields will be restored.
        *
        * @throws   IOException
        *           In case of I/O errors.
        * @throws   ClassNotFoundException
        *           If payload can't be instantiated.
        */
       @Override
       public void readExternal(ObjectInput in)
       throws IOException,
              ClassNotFoundException
       {
          id = readLong(in);
       }
    }