数据库中的 toBuilder() 与 Setter

Question

I am trying to save data in database with OneToOne mapping in bidirectional way. I have used toBuilder and setter and got different result in Database. By using setter:

        Question question = Question.builder().quest("What is Pythonn ?").answer(null).build();
        Answer answer = Answer.builder().answer("Python is language").que(question).build();
        answer.setQue(question);
        question.setAnswer(answer);
        Question question2 = Question.builder().quest("How are you ?").answer(null).build();
        Answer answer2 = Answer.builder().answer("I am fine").build();
        answer2.setQue(question2);
        question2.setAnswer(answer2);
        session.save(question);
        session.save(question2);

the result in db

question_table

Answer table

By using toBuilder

 answer.toBuilder().que(question).build();
 question = question.toBuilder().answer(answer).build();
 answer2.toBuilder().que(question2).build();
 question2 = question.toBuilder().answer(answer2).build();

The result in db: question_table

answer_table

Why toBuilder is not working while setter is working ?

Answer 1

You don't save a reference to question2 in answer2. That's why answer 2 has a null value for the question column.

Answer answer2 = Answer.builder().answer("I am fine").build();
 answer2.toBuilder().que(question2).build();

And you use question in the builder for question2. That's why there are multiple entries for question 1.

question2 = question.toBuilder().answer(answer2).build();

As for first question row with a null value for answer, I'm not sure where that's coming from.