spring data - Mongodb - findBy Method for nested objects

Question

I have two domain objects,

@Document public class PracticeQuestion {       private int userId;      private List<Question> questions;  // Getters and setters }  @Document public class Question {       private int questionID;      private String type;  // Getters and setters } 

My JSON doc is like this,

{     "_id" : ObjectId("506d9c0ce4b005cb478c2e97"),     "userId" : 1,     "questions" : [         {             "questionID" : 1,             "type" : "optional"           },         {              "questionID" : 3,              "type" : "mandatory"         }     ] } 

I have to update the "type" based on userId and questionId, so I have written a findBy query method inside the custom Repository interface,

public interface CustomRepository extends MongoRepository<PracticeQuestion, String> {      List<PracticeQuestion> findByUserIdAndQuestionsQuestionID(int userId,int questionID);        } 

My problem is when I execute this method with userId as 1 and questionID as 3, it returns the entire questions list irrespective of the questionID. Is the query method name valid or how should I write the query for nested objects.

Thanks for any suggestion.

Answer 1

Just use the @Query annotation on that method.

public interface CustomRepository extends MongoRepository<PracticeQuestion, String> {      @Query(value = "{ 'userId' : ?0, 'questions.questionID' : ?1 }", fields = "{ 'questions.questionID' : 1 }")     List<PracticeQuestion> findByUserIdAndQuestionsQuestionID(int userId, int questionID);  } 

By adding the fields part of the @Query annotation, you are telling Mongo to only return that part of the document. Beware though, it still returns the entire document in the same format - just missing everything you did not specify. So your code will still have to return List<PracticeQuestion> and you will have to do:

foreach (PracticeQuestion pq : practiceQuestions) {     Question q = pq.getQuestions().get(0); // This should be your question. }