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.mixins.system;
  
  import java.lang.annotation.ElementType;
  import java.lang.annotation.Retention;
  import java.lang.annotation.RetentionPolicy;
  import java.lang.annotation.Target;
  
  import org.apache.causeway.applib.annotation.Editing;
  import org.apache.causeway.applib.annotation.Property;
  
  /**
   * Extends {@link HasInteractionId} to add a strictly monotonically increasing
   * sequence number.
   *
   * <p>
   *     There are two different use cases for this:
   * </p>
   * <ul>
   *     <li>
   *         <p>
   *             The first is to identify different transactions within the overall
   *             {@link org.apache.causeway.applib.services.iactn.Interaction}.
   *         </p>
   *         <p>
   *             In the vast majority of cases there will only be a single transaction
   *             per {@link org.apache.causeway.applib.services.iactn.Interaction}, but this
   *             isn't <i>always</i> the case as domain objects may on occasion need to
   *             explicitly manage transaction boundaries using
   *             {@link org.apache.causeway.applib.services.xactn.TransactionService}.
   *         </p>
   *     </li>
   *     <li>
   *         <p>
   *             The second is to identify different executions within the overall
   *             {@link org.apache.causeway.applib.services.iactn.Interaction}.
   *         </p>
   *         <p>
   *             In the vast majority of cases there will only be a single execution
   *             per {@link org.apache.causeway.applib.services.iactn.Interaction}, but this
   *             isn't <i>always</i> the case; sometimes a top-level execution will cause
   *             another execution to occur, using the {@link org.apache.causeway.applib.services.wrapper.WrapperFactory}.
   *         </p>
   *     </li>
   * </ul>
   * <p>
   *     These two different sequences are independent of each other.
   * </p>
   *
   *
   * @since 2.0 {@index}
   */
  public interface HasInteractionIdAndSequence extends HasInteractionId {
  
      @Property(
              editing = Editing.DISABLED
      )
      @Target({ ElementType.METHOD, ElementType.FIELD, ElementType.PARAMETER, ElementType.ANNOTATION_TYPE })
      @Retention(RetentionPolicy.RUNTIME)
      @interface Sequence {
          boolean NULLABLE = false;
          String ALLOWS_NULL = "false";
      }
  
      /**
       * Holds the sequence number uniquely an &quot;event&quot; within the overall
       * {@link org.apache.causeway.applib.services.iactn.Interaction}.
       *
       * <p>
       *     The &quot;event&quot; could be a member execution (an action invocation or property edit),
       *     or could be a transaction.
       * </p>
       */
      @Sequence
      int getSequence();
  }
  