[FIXED] Transaction getting rolled back on persisting the entity from Many to one side

Issue

I have this association in the DB -

I want the data to be persisted in the tables like this -

The corresponding JPA entities have been modeled this way (omitted getters/setters for simplicity) -

STUDENT Entity -

@Entity 
@Table(name = "student")
public class Student {
    @Id
    @SequenceGenerator(name = "student_pk_generator", sequenceName = 
                              "student_pk_sequence", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = 
                               "student_pk_generator")
    @Column(name = "student_id", nullable = false)
    private Long studentId;

    @Column(name = "name", nullable = false)
    private String studentName;

    @OneToMany(mappedBy = "student", cascade = CascadeType.ALL)
    private Set<StudentSubscription> studentSubscription;
}

STUDENT_SUBSCRIPTION Entity -

@Entity
@Table(name = "student_subscription")
@Inheritance(strategy = InheritanceType.JOINED)
public abstract class StudentSubscription {
    @Id
    private Long studentId;

    @ManyToOne(optional = false)
    @JoinColumn(name = "student_id", referencedColumnName = "student_id")
    @MapsId
    private Student student;

    @Column(name = "valid_from")
    private Date validFrom;

    @Column(name = "valid_to")
    private Date validTo;
}

LIBRARY_SUBSCRIPTION Entity -

@Entity
@Table(name = "library_subscription", 
       uniqueConstraints = {@UniqueConstraint(columnNames = {"library_code"})})
@PrimaryKeyJoinColumn(name = "student_id")
public class LibrarySubscription extends StudentSubscription {

    @Column(name = "library_code", nullable = false)
    private String libraryCode;

    @PrePersist
    private void generateLibraryCode() {
        this.libraryCode = // some logic to generate unique libraryCode
    }

}

COURSE_SUBSCRIPTION Entity -

@Entity
@Table(name = "course_subscription", 
       uniqueConstraints = {@UniqueConstraint(columnNames = {"course_code"})})
@PrimaryKeyJoinColumn(name = "student_id")
public class CourseSubscription extends StudentSubscription {

    @Column(name = "course_code", nullable = false)
    private String courseCode;

    @PrePersist
    private void generateCourseCode() {
        this.courseCode = // some logic to generate unique courseCode
    }
}

Now, there is a Student entity already persisted with the id let's say - 100. Now I want to persist this student's library subscription. For this I have created a simple test using Spring DATA JPA repositories -

@Test
public void testLibrarySubscriptionPersist() {
    Student student = studentRepository.findById(100L).get();
    StudentSubscription librarySubscription = new LibrarySubscription();
    librarySubscription.setValidFrom(//some date);
    librarySubscription.setValidTo(//some date);
    librarySubscription.setStudent(student);
    studentSubscriptionRepository.save(librarySubscription);
}

On running this test I am getting the exception -

org.springframework.dao.InvalidDataAccessApiUsageException: detached entity passed to persist: com.springboot.data.jpa.entity.Student; nested exception is org.hibernate.PersistentObjectException: detached entity passed to persist: com.springboot.data.jpa.entity.Student

To fix this I attach a @Transactional to the test. This fixed the above exception for detached entity, but the entity StudentSubscription and LibrarySubscription are not getting persisted to the DB. In fact the transaction is getting rolled back.

Getting this exception in the logs -

INFO 3515 --- [           main] o.s.t.c.transaction.TransactionContext   : Rolled back transaction for test: [DefaultTestContext@35390ee3 testClass = SpringDataJpaApplicationTests, testInstance = com.springboot.data.jpa.SpringDataJpaApplicationTests@48a12036, testMethod = testLibrarySubscriptionPersist@SpringDataJpaApplicationTests, testException = [null], mergedContextConfiguration = [MergedContextConfiguration@5e01a982 testClass = SpringDataJpaApplicationTests, locations = '{}', classes = '{class com.springboot.data.jpa.SpringDataJpaApplication}', contextInitializerClasses = '[]', activeProfiles = '{}', propertySourceLocations = '{}', propertySourceProperties = '{org.springframework.boot.test.context.SpringBootTestContextBootstrapper=true}', contextCustomizers = set[org.springframework.boot.test.context.filter.ExcludeFilterContextCustomizer@18ece7f4, org.springframework.boot.test.json.DuplicateJsonObjectContextCustomizerFactory$DuplicateJsonObjectContextCustomizer@264f218, org.springframework.boot.test.mock.mockito.MockitoContextCustomizer@0, org.springframework.boot.test.web.client.TestRestTemplateContextCustomizer@2462cb01, org.springframework.boot.test.autoconfigure.actuate.metrics.MetricsExportContextCustomizerFactory$DisableMetricExportContextCustomizer@928763c, org.springframework.boot.test.autoconfigure.properties.PropertyMappingContextCustomizer@0, org.springframework.boot.test.autoconfigure.web.servlet.WebDriverContextCustomizerFactory$Customizer@7c3fdb62, org.springframework.boot.test.context.SpringBootTestArgs@1, org.springframework.boot.test.context.SpringBootTestWebEnvironment@1ad282e0], contextLoader = 'org.springframework.boot.test.context.SpringBootContextLoader', parent = [null]], attributes = map['org.springframework.test.context.event.ApplicationEventsTestExecutionListener.recordApplicationEvents' -> false]]

Now I have couple of questions -

1. Why am I getting detached entity exception. When we fetch an entity from the DB, Spring Data JPA must be using entityManager to fetch the entity. The fetched entity gets automatically attached to the persistence context right ?

2. On attaching @Transactional on the test, why the transaction is getting rolledback, and no entity is getting persisted. I was expecting the two entities - StudentSubscription and LibrarySubscription should've been persisted using the joined table inheritance approach.

I tried many things but no luck. Seeking help from, JPA and Spring DATA experts :-)

Thanks in advance.

Solution

The transaction is getting rolled back because the test is doing DB updates in the test method. @Transactional does auto rollback if the transaction includes any update DB. Also here is the compulsion to use transaction because EntityManager gets closed as soon as the Student entity gets retrieved, so to keep that open the test has to be within the transactional context.

Probably if I had used a testDB for my testcases then probably spring wouldn't haveve been rolling back this update.

Will setup an H2 testDb and perform the same operation there and will post the outcome.

Thanks for the quick help guys. :-)

Answered By - Kshitij
Answer Checked By - Marilyn (JavaFixing Volunteer)