JPA prevent entity from being saved - spring

Question

I've the following db schema:
account -< account_role >- role
Summing up: an account can be tied to multiple roles and account_role is a join table. roles is predefined and roles are inserted to DB in a migration.
Unfortunately on new account creating hibernate tries to insert the role to the table as well which results in the following exception:
org.postgresql.util.PSQLException: ERROR: duplicate key value violates unique constraint "role_role_name_key"
Detail: Key (role_name)=(CUSTOMER) already exists.
How can I configure the relation to prevent the insertion?
Below mentioned classes:
Role
import javax.persistence.*;
import static javax.persistence.EnumType.STRING;
#Entity
#Table(name = "ROLE")
class Role {
#Id
#Column(name = "ROLE_NAME")
#Enumerated(STRING)
private RoleName role;
//getters, setters, constructors
}
and
Account
import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;
import static javax.persistence.FetchType.EAGER;
import static javax.persistence.GenerationType.SEQUENCE;
#Entity
#Table(name = "ACCOUNT")
public class Account {
#Id
#SequenceGenerator(allocationSize = 1, sequenceName = "ACCOUNT_PK_SEQ", name = "ACCOUNT_PK_SEQ")
#GeneratedValue(generator = "ACCOUNT_PK_SEQ", strategy = SEQUENCE)
#Column(name = "ID")
private Long id;
#Column(name = "USERNAME")
private String username;
#ManyToMany(fetch = EAGER)
#JoinTable(
name = "ACCOUNT_ROLE",
joinColumns = #JoinColumn(name = "USERNAME", referencedColumnName = "USERNAME"),
inverseJoinColumns = #JoinColumn(name = "ROLE_NAME", referencedColumnName = "ROLE_NAME")
)
private Set<Role> roles = new HashSet<>();
//getters, setters, constructor
}
Here is the code responsible for saving new account:
#Transactional
public Account createNewAccount(Account account, String password) {
validator.validateNewAccount(account, password);
String email = account.getUsername().toLowerCase();
checkIfEmailAlreadyTaken(email);
LOG.info("Creating new account for username: '{}'.", account.getUsername());
account.setPassword(encodePassword(password));
account = repository.save(account);
return account;
}
Object of an Account class is created automatically from the request.
The full exception stacktrace can be found here.

Answer 1

The problem is caused by
#Id
#Column(name = "ROLE_NAME")
#Enumerated(STRING)
The JPA spec says :
2.1.4 Primary Keys and Entity Identity
The primary key (or field or property of a composite primary key) should be one of the following types: any Java primitive type; any primitive wrapper type; java.lang.String; java.util.Date; java.sql.Date. In general, however, approximate numeric types (e.g., floating point types) should never be used in primary keys. Entities whose primary keys use types other than these will not be portable.
So the combination of #Id and #Enumeration seems not allowed as you are using an enum as id.
With your current code you can write only as many roles as the enum RoleName has elements. These are the predifined roles of your system.
You should do that once on startup (or otherwise make sure they exist)
Add the annotation
#Column(insertable=false, updatable=false)
to Account.roles, this tells the JPA provider, to not insert or update the roles, when an Account is inserted or updated.
This should work.