org.postgresql.util.PSQLException：错误：列 user0_.id 不存在 - 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

Answer 2

For people getting this exception ,In postgres Whenever you write an Entity Class try to associate it with the correct schema (where your table is present), like this:

@Entity
@Table(name = "user", schema = "users_details")
public class User implements Serializable{

    @Column(name = "id")
    Long id;    //long is not recommended

   // Other data
}

As @YCF_L has said Don't use Upper_case letters in a table name or column name otherwise you will get this exception.

This convention becomes more important when their is a scenario where you have to auto generate the tables from entity classes or vice-versa.

Answer 3

Should add schema name on the Entity class. For this example, when the schema name is public

@Table(name = "user", schema = "public")

See the PostgreSQL Admin view below

See here for more about SpringBoot Java and Postgre SQL connectivity: https://cmsoftwaretech.wordpress.com/2020/04/25/springboot-thymleaf-using-postgresql/

Answer 4

I obtained using general names like user are making troubles in the app.

I got the same issue as reported here with the following simple entity.

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.SequenceGenerator;

@Entity
public class User implements Serializable {

    private static final long serialVersionUID = 6843302791607583447L;

    @Id
    @SequenceGenerator(name = "user_id_seq", sequenceName = "user_id_seq", allocationSize = 1)
    @GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "user_id_seq")
    private Long id;

    @Column
    private String name;

    @Column
    private String password;

    @Override
    public String toString() {
        return name;
    }

    public Long getId() {
        return id;
    }

    public String getName() {
        return name;
    }

    public void setName(final String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(final String password) {
        this.password = password;
    }

}

All i did was renaming the entity from User to Sessionxuser (and renaming the datatable from user to sessionxuser to fix this issue.

Schema was still public .

Since pre- or postfix some names like mycoolappuser or usermycoolapp to avoid troubles like this.

Find below a list with reserved keywords and literals preventing using as table, column, and further customized names.

https://www.postgresql.org/docs/8.1/sql-keywords-appendix.html

In this case user is preserved for PostgreSQL , SQL:2003 , SQL:1999 and SQL-92 .

Answer 5

Use: @GeneratedValue(strategy = GenerationType.IDENTITY)

In your POJO class Id Field. This thing solved my error.

Answer 6

尝试从 pg 管理控制台drop table schema_name.table_name （ drop table schema_name.table_name ）并确保您的实体类正确注释。例如实体类上的@Table(name = "table_name", schema = "schema_name")

Answer 7

In addition to all previous correct answers, I'd like to say that the positioning of annotations @Column and @GeneratedValue also matters. You want to have both these annotations above either the specific field or getter method, but not separately ( not one annotation above the getter and the other above the field). It worked for me at least.

Answer 8

I fixed the issue by altering the column name from nameLikeThis to name_like_this

ALTER TABLE table RENAME nameLikeThis to name_like_this;