org.postgresql.util.PSQLException: ERROR: column user0_.id does not exist - Hibernate

Question

I have a model class that is mapped to a postgres database using hibernate. My model class is:

@Entity
@Table(name="USER")
public class User {

    @Id 
    @GeneratedValue
    @Column(name="id")
    private long id;

    @Column(name="username", unique=true)
    private String username;

    @Column(name="email")
    private String email;

    @Column(name="created")
    private Timestamp created;

    public User(long id, String username, String email) {
        this.id = id;
        this.username = username;
        this.email = email;
    }
}

I try to retrieve the user with username "adam" using the below query:

tx = session.beginTransaction();
TypedQuery<User> query = session.createQuery("FROM User u WHERE u.username = :username", User.class).setParameter("username", "adam");
user = query.getSingleResult();

I get an exception that says:

org.postgresql.util.PSQLException: ERROR: column user0_.id does not exist

My database from bash shell looks like:

How does hibernate map class attributes to table columns? Does it match based on the @Column(name="username") only or does it also try to match based on datatypes and constraints such as unique/auto-increment?

Answer 1

Solution

In PostgreSQL you have to specify the name of schema like so :

@Table(name="table_name", schema = "myapp")
                          ^^^^^^^^^^^^^^^^

Long Story

you got this error :

org.postgresql.util.PSQLException: ERROR: column user0_.id does not exist

because when you create a database in PostgreSQL, it create a default schema named public, so when you don't specify the name in the Entity then Hibernate will check automatically in the public schema.

---

Good practices

1. Don't use Upper letters in the name of database, schema, tables or columns in PostgreSQL. Else you should to escape this names with quotes, and this can cause Syntax errors, so instead you can use :

@Table(name="table_name", schema = "schame_name")
             ^^^^^^^^^^             ^^^^^^^^^^^

2. the keyword USER is reserved keyword in PostgreSQL take a look at

+----------+-----------+----------+-----------+---------+
| Key Word |PostgreSQL |SQL:2003  | SQL:1999  | SQL-92  |
+----------+-----------+----------+-----------+---------+
|  ....        ....       ....       ....       ....    |
+----------+-----------+----------+-----------+---------+
| USER     |  reserved |reserved  | reserved  | reserved|
+----------+-----------+----------+-----------+---------+

3. to difference between Dto and Entity its good practice to use Entity in the end of the name of your Entity for example UserEntity