Play Framework: JPA one-to-many relationship between three entities? - sql

Question

I am building a web application using the play framework and I am running into problems with creating the database model using this schema
**Client** – (many to many) – **Events**
\ /
(one to many) (one to many)
\ /
**COMMENTS**
I am able to create and add the relationships
Event event = new Event("Party");
Client client = new Client("test#gmail.com","fname","lname","street","phonenum");
Comment comment = new Comment("test comment!");
//Add relationships
client.addEvent(event);
event.addClient(client);
event.addComment(comment);
comment.addEvent(event);
event.addClient(client);
client.addComment(comment);
But when I try to persist the data
client.save();
event.save();
comment.save();
I receive the error
[error] Test CommentModelTest.testClientEventCommentRelationship failed:
javax.persistence.PersistenceException: org.h2.jdbc.JdbcSQLException: Unique index or primary
key violation: "PRIMARY_KEY_4A ON PUBLIC.EVENT_CLIENT(EVENT_ID, CLIENT_EMAIL)"; SQL statement:
[error] insert into event_client (client_email, event_id) values (?, ?) [23505-172]
The class definitions are shown below, I would really appreciate it if someone could help me solve this issue. Am I defining the relationship incorrectly? Thanks in advance!
Client Class:
#Entity
public class Client extends Model {
#Id
public String email;
#Required
public String firstName;
#Required
public String lastName;
public String homeAddress;
public String phoneNumber;
#ManyToMany(mappedBy="clients", cascade=CascadeType.ALL)
public List<Event> events = new ArrayList<Event>();
#OneToMany(mappedBy="client", cascade=CascadeType.ALL)
public List<Comment> comments = new ArrayList<Comment>();
Event Class:
#Entity
public class Event extends Model {
#Id
public Long id;
#Required
public String eventName;
#ManyToMany(cascade=CascadeType.ALL)
public List<Client> clients = new ArrayList<Client>();
#OneToMany(mappedBy="event", cascade=CascadeType.ALL)
public List<Comment> comments = new ArrayList<Comment>();
Comment Class:
#Entity
public class Comment extends Model {
#Id
public Long id;
#Required
public String message;
#ManyToOne(cascade=CascadeType.PERSIST)
public Client client;
#ManyToOne(cascade=CascadeType.PERSIST)
public Event event;
---Edit:-------------------------------
I realized where I went wrong. In case you are running into a similar error, check to see if you are using the models correctly! In my JUnit test I tried adding the same client to an event twice, causing the primary key (email) to be duplicated.
the corrected relationship code should be as follows:
client.addEvent(event);
event.addClient(client);
event.addComment(comment);
comment.addEvent(event);
comment.addClient(client);
client.addComment(comment);

Answer 1

The exception says that you are trying to add the same relationship twice.
"PRIMARY_KEY_4A ON PUBLIC.EVENT_CLIENT(EVENT_ID, CLIENT_EMAIL)"
I guess this is on the table between the events and the clients, so it maps the ManyToMany relationship.
client.addEvent(event);
HERE --> event.addClient(client);
event.addComment(comment);
comment.addEvent(event);
HERE --> event.addClient(client);
client.addComment(comment);
It's added twice and there is a unique index that prevents that.