title: Spring-data-mongodb not persist multiple objects on list
body: <p>I am using Spring-data-mongodb and i can persist an object on a list, but when i try to add another, it doesn't work, the application doesn't throw an exception.</p>
  
  <p>this is my Json:</p>
  
  <pre><code>[
    {
      idUser: "4a9f10d9-e19f-42af-ba00-891a567cc41f",
      login: "peter",
      password: "mypassword",
      email: "peter@eeee.com",
      patients: 
        [
          {
            idPatient: "d31e8052-36d3-4285-9f97-454f3437812d",
            name: "ada",
            birthday: 1363474800000,
            idUser: "4a9f10d9-e19f-42af-ba00-891a567cc41f",
            region: 
            {
              idRegion: "d8acfa45-486e-49e0-b4e6-edde6743cf30",
              name: "Madrid"
            },
            personalCalendars: null
          },
          null
        ]
     }
  ]
  </code></pre>
  
  <p>As you can see, my first Patient element is correctly, and the second was insert as null.</p>
  
  <p>I leave my code:</p>
  
  <p>User.java</p>
  
  <pre><code>@Document(collection = "users")
  public class User implements Serializable {
  
  private static final long serialVersionUID = 1L;
  
  @Id
  private String id;
  
  @Indexed
  private UUID idUser;
  
  @Indexed(unique = true)
  private String login;
  
  private String password;
  
  @Indexed(unique = true)
  private String email;
  
  @DBRef
  private List&lt;Patient&gt; patients;
  
  @PersistenceConstructor
  public User(UUID idUser, String login, String password, String email, List&lt;Patient&gt; patients){
      this.idUser = idUser;
      this.login = login;
      this.password = password;
      this.email = email;
  this.patients = patients;
  }
  </code></pre>
  
  <p>Patient.java</p>
  
  <pre><code>@Document(collection = "patients")
  public class Patient implements Serializable {
  
  private static final long serialVersionUID = 1L;
  
  @Id
  private String id;
  
  @Indexed
  private UUID idPatient;
  
  private String name;
  
  private Date birthday;
  
  private UUID idUser;
  
  private Region region;
  
  @Transient
  private List&lt;PersonalCalendar&gt; personalCalendars;
  
  @PersistenceConstructor
  public Patient(UUID idPatient, String name, Date birthday,UUID idUser, Region region){
      this.idPatient = idPatient;
      this.name = name;
      this.birthday = birthday;
      this.idUser = idUser;
      this.region = region;
  }
  </code></pre>
  
  <p>and the DAO whereI do the insert.</p>
  
  <pre><code>@Override
  public Patient createPatient(User user, Patient patient) {
      this.mongoOps.save(patient , "patients");
      this.mongoOps.save(user , "users");
      return this.getPatientById(patient.getIdPatient());
  }
  </code></pre>
  
  <p>The console returns this, but no persists the patient:</p>
  
  <pre><code>15:16:16.718 [tomcat-http--6] DEBUG o.s.data.mongodb.core.MongoTemplate - Saving DBObject containing fields: [_class, _id, idPatient, name, birthday, idUser, region]
  15:16:16.723 [tomcat-http--6] DEBUG o.s.data.mongodb.core.MongoDbUtils - Getting Mongo Database name=[application]
  15:16:16.747 [tomcat-http--6] DEBUG org.mongodb.driver.protocol.insert - Inserting 1 documents into namespace application.patients on connection [connectionId{localValue:2, serverValue:119}] to server 127.0.0.1:27017
  15:16:16.761 [tomcat-http--6] DEBUG org.mongodb.driver.protocol.insert - Insert completed
  </code></pre>
  
  <p>I need help.
  Thanks a lot</p>