Add row to join table using JPA - jpa

Question

I'm using JPA 2.0 and I'm using a generated schema.
Here is my mapping:
#Entity
#Table(name = "CBV_USER")
public class CbvUser implements Serializable {
private static final long serialVersionUID = 1L;
#Id
#Basic(optional = false)
#Column(name = "Login")
private String login;
#Basic(optional = false)
#Column(name = "Password")
private String password;
#Basic(optional = false)
#Column(name = "Email")
private String email;
#Basic(optional = false)
#Column(name = "FirstName")
private String firstName;
#Basic(optional = false)
#Column(name = "LastName")
private String lastName;
#Basic(optional = false)
#Column(name = "Id")
private String id;
#Column(name = "Score")
private BigDecimal score;
#JoinTable(name = "FRIENDSHIP", joinColumns = {
#JoinColumn(name = "Login0", referencedColumnName = "Login")}, inverseJoinColumns = {
#JoinColumn(name = "Login1", referencedColumnName = "Login")})
#ManyToMany
private List<CbvUser> cbvUserList2;
#ManyToMany(mappedBy = "cbvUserList2")
private List<CbvUser> cbvUserList3;
public CbvUser() {
}
public CbvUser(String login) {
this.login = login;
}
public CbvUser(String login, String password, String email, String firstName, String lastName, String id) {
this.login = login;
this.password = password;
this.email = email;
this.firstName = firstName;
this.lastName = lastName;
this.id = id;
}
public String getLogin() {
return login;
}
public void setLogin(String login) {
this.login = login;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public BigDecimal getScore() {
return score;
}
public void setScore(BigDecimal score) {
this.score = score;
}
public List<CbvUser> getCbvUserList2() {
return cbvUserList2;
}
public void setCbvUserList2(List<CbvUser> cbvUserList2) {
this.cbvUserList2 = cbvUserList2;
}
public List<CbvUser> getCbvUserList3() {
return cbvUserList3;
}
public void setCbvUserList3(List<CbvUser> cbvUserList3) {
this.cbvUserList3 = cbvUserList3;
}
#Override
public int hashCode() {
int hash = 0;
hash += (login != null ? login.hashCode() : 0);
return hash;
}
#Override
public boolean equals(Object object) {
// TODO: Warning - this method won't work in the case the id fields are not set
if (!(object instanceof CbvUser)) {
return false;
}
CbvUser other = (CbvUser) object;
if ((this.login == null && other.login != null) || (this.login != null && !this.login.equals(other.login))) {
return false;
}
return true;
}
#Override
public String toString() {
return "models.CbvUser[login=" + login + "]";
}
}
My problem is that I can't figure out how to add a new row in the Join Table FRIENDSHIP through a specific CbvUser or through an EntityManager.
I'll be really grateful for any help.

Answer 1

Something like this should work:
CbvUser user1 = new CbvUser();
...
CbvUser user2 = new CbvUser();
...
// declare user2 as a friend of user1
List<CbvUser> cbvUserList2 = new ArrayList<CbvUser>();
cbvUserList2.add(user2);
user1.setCbvUserList2(cbvUserList2);
// declare user1 as a friend of user2
List<CbvUser> cbvUserList3 = new ArrayList<CbvUser>();
cbvUserList3.add(user1);
user2.setCbvUserList3(cbvUserList3);
em.persist(user1);
em.persist(user2);
em.flush();
The friendship relation is a (self-referencing) bidirectional association, so you must set both sides of the link correctly (from user1 to user2 and from user2 to user1).

Answer 2

Providing a public add/remove that maintains referential integrity might be even more elegant here.