Hibernate : How to use @Column Annotation

Points To Remember

• @Column annotation is used to define the column name, type, constraints.
• It should be used with the fields either above the getter or above field declaration.

The @Column annotation can take the following configuration.

Property	Type	Default Value	Description
name	Optional	""	The name of the column. Defaults to the property or field name
unique	Optional	false	Whether the column is a unique key.
nullable	Optional	true	Whether the database column is nullable.
insertable	Optional	true	Whether the column is included in SQL INSERT statements generated by the persistence provider.
updatable	Optional	true	Whether the column is included in SQL UPDATE statements generated by the persistence provider.
columnDefinition	Optional	""	The SQL fragment that is used when generating the DDL for the column.
table	Optional	""	The name of the table that contains the column. If absent the column is assumed to be in the primary table.
length	Optional	255	The column length. (Applies only if a string-valued column is used.
precision	Optional	0	The precision for a decimal (exact numeric) column. (Applies only if a decimal column is used.)
scale	Optional	0	The scale for a decimal (exact numeric) column (Applies only if a decimal column is used.)

How to use @Column Annotation in Hibernate

We will we taking the example of @Entity annotation to show the changes made by @Column annotation.

package com.ekiras.domian;

import com.ekiras.enums.Gender;

import javax.persistence.*;
import java.util.Date;

@Entity
public class User {

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

    @Column(name = "name",length = 100)
    private String name;
    
    @Column(name = "current_age")
    private Integer age;

    @Column(name = "address",columnDefinition = "text")
    private String address;
    
    @Column
    private Gender gender;

    @Column(name = "email",updatable = false, nullable = false, unique = true)
    private String email;

    private Long mobile;

    @Temporal(value = TemporalType.DATE)
    private Date dateCreated;

   // GETTERS AND SETTERS
}

The above Entity definition will create the output as shown in the image below.

What @Column annotation did is

• mapped age to current_age in database.
• changed address ddl type to text.
• added nullable and unique constraints to field email.
• changes name ddl from varchar(255) to varchar(100).

Also read about the following

• See the use of @Temporal annotation in hibernate.
• See the how to use columnDefinition property of @Column annotation.