content: /*
   *  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.causeway.applib.services.commanddto.processor;
  
  import org.apache.causeway.schema.cmd.v2.CommandDto;
  
  /**
   * Refine (or possibly ignore) a command when replicating from primary
   * to secondary.
   * 
   * @since 1.x {@index}
   */
  public interface CommandDtoProcessor {
  
      /**
       * The implementation can if necessary refine or alter the
       * {@link CommandDto} to be replicated from primary to secondary.
       *
       * <p>
       *     That said, the most common use case is to return <code>null</code>,
       *     which results in the command effectively being ignore.
       * </p>
       *
       * @param commandDto - to be processed
       * @return <tt>null</tt> means that the command's DTO is effectively
       *         excluded.
       */
      CommandDto process(CommandDto commandDto);
  
      /**
       * Convenience implementation to simply indicate that no DTO should be
       * returned for a command, effectively ignoring it for replication purposes.
       */
      class Null implements CommandDtoProcessor {
          @Override
          public CommandDto process(final CommandDto commandDto) {
              return null;
          }
      }
  
  }
  