I tried sending this in POSTMAN:

{
    "title": "the",
    "type": "MCQ",
    "teacher_id": "2",
    "questions" : [{
    "content": "Who are you",
    "answers":[{
        "content": "you",
        "correct" : "true"
    }]
  }],
    "status": "OPEN"
}

Tried switching media types but it didn’t work, I couldn’t send anything to that mapping successfully, I think it might have to do with the questions list that also has an answers list.
Get the error: "error": "Unsupported Media Type", "trace": "org.springframework.web.HttpMediaTypeNotSupportedException: Content-Type 'application/json;charset=UTF-8'

• Here’s the entity:

package com.academy.exams.entity;
import com.fasterxml.jackson.annotation.JsonManagedReference;
import jakarta.annotation.PostConstruct;
import jakarta.persistence.*;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;


import java.util.List;

@Entity
@Table(name = "Exam")
public class Exam {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "exam_id")
    private Long examId;

    private String title;

    @Enumerated(EnumType.STRING)
    private ExamType type;

    @JsonManagedReference
    @OneToMany(mappedBy = "exam", cascade = CascadeType.ALL)
    private List<Question> questions;

    @Column(name = "teacher_id")
    private Long teacherId;

    private String status;

    public Long getId() {
        return examId;
    }

    public void setId(Long examId) {
        this.examId = examId;
    }

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public ExamType getType() {
        return type;
    }

    public void setType(ExamType type) {
        this.type = type;
    }

    public List<Question> getQuestions() {
        return questions;
    }

    public void setQuestions(List<Question> questions) {
        this.questions = questions;
    }

    public Long getTeacherId() {
        return teacherId;
    }

    public void setTeacherId(Long teacherId) {
        this.teacherId = teacherId;
    }

    public String getStatus() {
        return status;
    }

    public void setStatus(String status) {
        this.status = status;
    }

    @PostConstruct
    public void init() {
        System.out.println("Exam initialized");
    }
}

• Here’s the service, knowing I used this @Repository public interface ExamRepository extends JpaRepository<Exam, Long> {}:

 public Exam CreateExam(Exam exam){

        return examRepository.save(exam);
    }

• And here’s the controller:

package com.academy.exams.controller;
import com.academy.exams.entity.Exam;
import com.academy.exams.service.ExamService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

import java.util.List;

@RestController
@RequestMapping("/exams")

public class ExamController {

    @Autowired
    private ExamService examService;

    @PostMapping("/create")
    public Exam createExam(@RequestBody Exam exam){
        return examService.CreateExam(exam);
    }
}

• Here’s the question Entity too:

package com.academy.exams.entity;
import com.academy.exams.entity.Exam;
import com.fasterxml.jackson.annotation.JsonBackReference;
import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import jakarta.persistence.*;
import java.util.List;

@Entity
@Table(name = "Question")

public class Question {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "question_id")
    private Long questionId;

    @Column(name = "content")
    private String content;

    @JsonBackReference
    @ManyToOne
    @JoinColumn(name = "exam_id")
    private Exam exam;

    @JsonBackReference
    @OneToMany(mappedBy = "question", cascade = CascadeType.ALL)
    private List<Answer> answers;

    public Long getId() {
        return questionId;
    }

    public void setId(Long id) {
        this.questionId = questionId;
    }

    public String getContent() {
        return content;
    }

    public void setContent(String content) {
        this.content = content;
    }

    public Exam getExam() {
        return exam;
    }

    public void setExam(Exam exam) {
        this.exam = exam;
    }

    public List<Answer> getAnswers() {
        return answers;
    }

    public void setAnswers(List<Answer> answers) {
        this.answers = answers;
    }
}

• And the answers entity:

package com.academy.exams.entity;

import com.fasterxml.jackson.annotation.JsonManagedReference;
import jakarta.persistence.*;

    @Entity
    @Table(name = "Answer")

    public class Answer {

        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        @Column(name ="answer_id")
        private Long answerId;

        private String content;

        @Column(name="correct")
        private Boolean correct;

        @JsonManagedReference
        @ManyToOne
        @JoinColumn(name = "question_id" )
        private Question question;

        public Long getId() {
            return answerId;
        }

        public void setId(Long answerId) {
            this.answerId = answerId;
        }

        public String getContent() {
            return content;
        }

        public void setContent(String content) {
            this.content = content;
        }

        public Boolean getCorrect() {
            return correct;
        }

        public void setCorrect(Boolean correct) {
            this.correct = correct;
        }
    }