title: Why is Spring Boot Starter Mongodb Reactive not saving the List fields of my entities?
body: <p>I can't figure out why the List fields of my entities are not being persisted when saved using Spring Boot Mongodb Reactive.</p>
  
  <p>This is how my Contact entity looks like:</p>
  
  <pre><code>@Data
  @Document
  public class Contact {
      private String id;
  
      @DBRef
      private User owner;
  
      private List&lt;String&gt; messageIds;
  
      private Message lastMessage;
  
      private LocalDateTime lastMessageAt;
  
      public boolean addMessageId(String message) {
          if (messageIds == null) {
              messageIds = new ArrayList&lt;&gt;();
          }
          return messageIds.add(message);
      }
  }
  </code></pre>
  
  <p>I save it using this repository:</p>
  
  <pre><code>public interface ContactRepository extends ReactiveMongoRepository&lt;Contact, String&gt; {
  
      Mono&lt;Contact&gt; findByOwnerId(String ownerId);
  
  }
  </code></pre>
  
  <p>Everything but the messageIds list is getting persisted just fine. I already switched from directly having a list of Messages, but this didn't help so far. </p>
  
  <p>The debugger also shows the messageIds list right there before the repo save call.</p>
  
  <p>Already searched for a solution without any luck. Am I missing the obvious here?</p>