title: org.axonframework.eventsourcing.IncompatibleAggregateException (Axon framework: Aggregate identifier must be non-null after applying an event)
body: <p>I try to config <strong>cqrs</strong> and <strong>event sourcing</strong> with axon.
  <strong>SeatReseveCreateCommand</strong> is work properly. but <strong>SeatReserveUpadateCommand</strong> is not work correct.</p>
  
  <p>this is my SeatReserve <strong>aggregate</strong> </p>
  
  <pre><code>@Aggregate
  public class SeatReserve {
      @AggregateIdentifier
      private String id;
      private String seatid;
      private Date date;
  
      @SuppressWarnings("unused")
      private SeatReserve() {
      }
  
      @CommandHandler
      public SeatReserve(SeatReseveCreateCommand seatReseveCreateCommand) {
          apply(new SeatReseveCreateEvent(seatReseveCreateCommand.getMyid(), seatReseveCreateCommand.getSeatId(),
                  seatReseveCreateCommand.getDate()));
      }
  
      @CommandHandler
      public SeatReserve(SeatReserveUpadateCommand upadateCommand) {
          apply(new SeatReserveUpadateEvent(id, upadateCommand.getSeatId()));
      }
  
      @EventSourcingHandler
      public void on(SeatReseveCreateEvent seatReseveCreateEvent) {
          this.id = seatReseveCreateEvent.getId();
          this.seatid = seatReseveCreateEvent.getSeatId();
          this.date = seatReseveCreateEvent.getDate();
      }
  
      @EventSourcingHandler
      public void on(SeatReserveChangeEvent upadateEvent) {
          seatid = upadateEvent.getSeatId();
      }
  
  }
  </code></pre>
  
  <p>this is my controller</p>
  
  <pre><code>@RestController
  public class TestController {
  
      private final CommandGateway commandGateway;
  
      public TestController(CommandGateway commandGateway) {
          this.commandGateway=commandGateway;
      }
  
      @PostMapping
      public String fileComplaint(@RequestBody Map&lt;String, String&gt; request) {
          String id = UUID.randomUUID().toString();
          SeatReseveCreateCommand command=new SeatReseveCreateCommand(id,request.get("seatid"),new Date(request.get("date")));
          commandGateway.send(command);
          return id;   
      }
      @PatchMapping
      public String fileComplaintUpdate(@RequestBody Map&lt;String, String&gt; request) {
          SeatReserveUpadateCommand command= new SeatReserveUpadateCommand(request.get("id"),request.get("seatid"));
          commandGateway.send(command);
          return request.get("id");
      }
  }
  </code></pre>
  
  <p>I try to send request using postman </p>
  
  <p>this is my create request </p>
  
  <p><a href="https://i.stack.imgur.com/d2nf6.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/d2nf6.png" alt="enter image description here"></a></p>
  
  <p>this is my update request</p>
  
  <p><a href="https://i.stack.imgur.com/il0tF.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/il0tF.png" alt="enter image description here"></a></p>
  
  <p>update make this error </p>
  
  <pre><code>2018-01-03 10:44:53.608  WARN 11138 --- [nio-8085-exec-1] o.a.c.gateway.DefaultCommandGateway      : Command 'com.thamira.research.api.bankaccount.SeatReserveUpadateCommand' resulted in org.axonframework.eventsourcing.IncompatibleAggregateException(Aggregate identifier must be non-null after applying an event. Make sure the aggregate identifier is initialized at the latest when handling the creation event.)
  </code></pre>
  
  <p>how can I solve this.</p>