catching ConstraintViolationException from jpa gives constraint name null value

Question

I use jpa and hibernate to persist my data.My model is

@Entity
@Table(name = "user", uniqueConstraints=@UniqueConstraint(columnNames={"username"}, name="username"))
public class User implements Serializable {
    @Transient
    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private int id;

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

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

    @Column(name = "user_role", nullable = false)
    private UserRole userRole;
}   

I am catching the ConstraintViolationException to catch if a user is violating a unique value. But when I try to access the constraintName using ConstraintViolationException.getConstraintName() gives me null value. How can I know which column violated the constraint so to warn the user?

Answer 1

尝试： cve.getCause().getMessage()