Last updated on May 7th, 2025
When we are creating a JPA Entity class then we need to sometimes customize column length for the database table.To set column length in JPA entity we can use @Column annotation with its length or columnDefinition attribute at the property of that entity class. In this topic, we will learn how to set column length in JPA Entity using different ways.
Different Ways to Set Column Length in JPA Entity
● Using @Column(length = n) Annotation
● Using @Column(columnDefinition = ” “) Annotation
Using @Column(length = n)
We can define the maximum length for a column by using this length attribute of the @Column annotation.
Example
import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import jakarta.persistence.Column
@Entity
public class User {
@Id
private Long id;
@Column(length = 50)
private String username;
@Column(length = 255) // Default length for VARCHAR
private String email;
// Constructors, Getters, and Setters
}How it works
● @Column(length = 50): It ensures the username column has a maximum of 50 characters. If a value exceeds from this length then the database will throw an error.
Using @Column(columnDefinition=” “) Annotation
If we need to specify column length explicitly at the database level, use the columnDefinition attribute of @Column annotation in the field of the JPA Entity class.
Example
import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import jakarta.persistence.Column
@Entity
public class Customer {
@Id
private Long id;
@Column(columnDefinition = "VARCHAR(150)")
private String address;
// Constructors, Getters, and Setters
}How it works
● It ensures that the address column is defined as VARCHAR(150) in the database.
● This method is database-dependent and may not work across all database providers.
Pros and Cons of the Approaches
| Approach | Pros | Cons |
| @Column(length = n) | Simple and standard | Only works for VARCHAR |
| @Column(columnDefinition= ” ”) | Full control over column definition | Not portable across databases |
For best results
● Use @Column(length = n) for defining length in the database.
● Use columnDefinition only when needed for database-specific constraints.
Conclusion
In this topic we learnt about how to set column length in JPA Entity using @Column with its attribute length and columnDefinition.