Spring-Data Hibernate JPA is not saving data into Join table

[nnanda]

Following are the entities and their relationships in my system

Entities:

1. Certification
2. Group
3. Exam

Relationship:

1. One Certification can have multiple Groups (One-to-Many)
2. One Group can have multiple Exams and one Exam can belong to multiple Groups (Many-to-Many)
3. Exam data is created through a separate use case
4. While creating Certifications, the user can add new Groups and associate pre-exising Exams.

I have created following tables for this:

1. demo_cert
2. demo_grp (it has a FK to demo_cert's ID column)
3. demo_exam
4. demo_exam_grp(group_id, exam_id)

Following code snippets show the Domain object definitions

@Entity
@Table(name="demo_nn_cert")
@Access(AccessType.FIELD)
public class DemoCert
{
    @Id
	@Column(name="ID")
	@GeneratedValue(strategy=GenerationType.AUTO, generator="CERT_SEQ")
	@SequenceGenerator(name="CERT_SEQ", sequenceName="demo_cert_seq")
	private Long id;
	
	@OneToMany(fetch=FetchType.LAZY, cascade=CascadeType.ALL, orphanRemoval=true, mappedBy="demoCert", targetEntity=DemoGrp.class)
	private Set<DemoGrp> groups;
	
	@Version
	private long version;
	
	// -- Other properties and their getter/setters
}

@Entity
@Table(name="demo_nn_grp")
@Access(AccessType.FIELD)
public class DemoGrp implements Serializable
{
	/**
	 * 
	 */
	private static final long serialVersionUID = 7438445502527409879L;

	@Id
	@Column(name="ID")
	@GeneratedValue(strategy=GenerationType.AUTO, generator="GROUP_SEQ")
	@SequenceGenerator(name="GROUP_SEQ", sequenceName="demo_group_seq")
	private Long id;
		
	@ManyToOne(cascade=CascadeType.ALL, fetch=FetchType.LAZY, targetEntity=DemoCert.class)
	@JoinColumn(name="CERT_ID")
	private DemoCert demoCert;
	
	@OneToMany(fetch=FetchType.LAZY, cascade=CascadeType.ALL, orphanRemoval=true, targetEntity=DemoExam.class)
	@JoinTable
	(
		name="DEMO_EXAM_GRP",
		joinColumns={@JoinColumn(name="GROUP_ID", referencedColumnName="ID")},
		inverseJoinColumns={@JoinColumn(name="EXAM_ID", referencedColumnName="ID")}
	)
	private Set<DemoExam> exams;
	
	// -- Other properties and getters/setters
}

@Entity
@Table(name="demo_nn_exam")
@Access(AccessType.FIELD)
public class DemoExam implements Serializable
{
	/**
	 * 
	 */
	private static final long serialVersionUID = 375151244325884919L;

	@Id
	@Column(name="ID")
	private long id;
	
	@Version
	private long version;
	
	// -- Other properties and getters/setters
}

To test, I am creating the entire object graph and call

EntityManager.persist(demoCert)

.

The issue I am facing is, instead of inserting data to join table

demo_exam_grp

, it is trying to insert into [code]demo_exam[c/ode] table and failing because the data is already present.

Could someone help me?

I am using

- Spring 3.1.1 (accessing JPA through Spring-Data module)
- Hibernate 4.1.1