Persisting a parent with existing children throws detached entity exception

Question

I have this many-many relationship between students and courses as in following JPA models

@Entity(name = "course_result")
public class CourseResult {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private BigInteger id;
    @ManyToOne(targetEntity = Student.class, cascade = CascadeType.ALL)
    @JoinColumn(name = "student_id")
    private Student student;
    @ManyToOne(targetEntity = Course.class, cascade = CascadeType.ALL)
    @JoinColumn(name = "course_id", referencedColumnName = "id")
    private Course course;
    private float grade;
}

@Entity
public class Course {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private BigInteger id;
    private String courseName;
    private String description;
    @OneToMany(mappedBy = "course", fetch = FetchType.EAGER)
    private Set<CourseResult> courseResult;
}

@Entity
public class Student {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private BigInteger id;
    private String studentName;
    private String studentClass;
    @OneToMany(mappedBy = "student", fetch = FetchType.EAGER)
    private Set<CourseResult> courseResult;
}

When persisting a CourseResult, I want a new course/student would be created if it not yet exists otherwise they'll be updated only. That's why I set the cascade type to ALL. T

However, it always throws an exception when I try to persist a new CourseResult with existing Student and Course, say both with Id = 1

    Student student = studentRepo.findById(BigInteger.ONE).get();
    Course course = courseRepo.findById(BigInteger.ONE).get();
    CourseResult courseResult = new CourseResult()
            .setCourse(course)
            .setStudent(student)
            .setGrade(1.5F);
    courseResultRepository.save(courseResult);

org.springframework.dao.InvalidDataAccessApiUsageException: detached entity passed to persist: org.example.domain.Course; nested exception is org.hibernate.PersistentObjectException: detached entity passed to persist: org.example.domain.Course

Do you have any idea why?

TIA,

score 0 · Answer 1 · answered Oct 06 '22 at 22:22

There are a couple of approaches you could try

Is there a Transaction around your Code ? It is not shown in your example. Ensure that the import is using the spring Transaction.

Try adding the courseResult to the other enities

Student student = studentRepo.findById(BigInteger.ONE).get();
Course course = courseRepo.findById(BigInteger.ONE).get();
student.getCourseResult().add()
CourseResult courseResult = new CourseResult()
    .setGrade(1.5F);
student.getCourseResult().add(courseResult);
course.getCourseResult().add(courseResult);

Try saving the CourseResult before adding it to the Objects. That way it might then be recognized by Hibernate as a managed entity

 Student student = studentRepo.findById(BigInteger.ONE).get();
 Course course = courseRepo.findById(BigInteger.ONE).get();
 student.getCourseResult().add()
 CourseResult courseResult = new CourseResult()
     .setGrade(1.5F);
 courseResultRepository.save(courseResult);
 courseResult.setStudent(student); 
 courseResult.setCourse(course); 
 courseResultRepository.save(courseResult);

Try adding

cascade = CascadeType.ALL

to

@OneToMany(mappedBy = "course", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
private Set<CourseResult> courseResult;

and

 @OneToMany(mappedBy = "student", fetch = FetchType.EAGER, cascade = CascadeType.ALL)
 private Set<CourseResult> courseResult;

Try using cascade= CascadeTyp.Mergeinsdead of cascade= CascadeTyp.ALL (PersistentObjectException: detached entity passed to persist thrown by JPA and Hibernate)

Thanks for your suggestions. Unfortunately, it not yet works — HieuHT, Oct 07 '22 at 12:58

Persisting a parent with existing children throws detached entity exception

1 Answers1