Hibernate: "Field 'id' doesn't have a default value"

java

hibernate-configuration

database-structure

orm-model

byAlex Kataev·Feb 9, 2025

Quickly resolve the "Field 'id' doesn't have a default value" error in Hibernate by adding the @Id and @GeneratedValue(strategy = GenerationType.IDENTITY) annotations to the id field:

@Entity
public class YourEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    // Here's a number that will grow but never go on a diet - our id!
}

This instructs Hibernate that the database should take charge of creating id values, embracing the AUTO_INCREMENT property in MySQL. If this quick fix doesn't solve your problem, continue reading for an in-depth analysis.

Aligning your ORM model and database structure

Mismatch between your ORM model and the database structure is a common root cause of this error, primarily if you've recently tweaked your ORM. Guarantee that modifications reach your database.

Create mode with hbm2ddl.auto

Using hbm2ddl.auto with the "create" setting can be your lifeboat. It recreates your schema on initialization, thus tackling id field nightmares:

<property name="hbm2ddl.auto">create</property>
//Congratulations, you've just waved a magic wand on the schema and it's reborn!

Employing SchemaExport and SchemaUpdate

You can rely on SchemaExport to scaffold your database from scratch, while SchemaUpdate will attempt to modify the currently-existing schema - though it might overlook some changes. In mission-critical applications, explicit migrations always outshine automated updates, preventing disparity.

Last resort measures

If the mountain doesn't come to Muhammad, Muhammad must go to the mountain. Consider manual interventions if all fails:

Drop the bomb: Manually drop the database and breathe new life into it with Hibernate as your application initializes. It's the nuclear option, but it can clear the deck.
Debugging: Bring Hibernate's SQL out of the closet through logging and adjust your configurations:

<property name="show_sql">true</property>
//It's like opening Pandora's box, but thankfully, no evils here, just SQL!

Before pulling the trigger, ensure you have a bulletproof backup of your valuable data.

Plowing through problematic scenarios

Decoding cryptic errors

Like a mystery novel, Hibernate errors can sometimes leave you hanging. When this happens, inspect the SQL commands that Hibernate generates to identify the real culprit.

GenerationType nuances

The behavior of SEQUENCE, TABLE, AUTO - the different GenerationType strategies- change based on the database dialect, introducing another layer of complexity. Being familiar with these can help you identify the right strategy and outrun the default value error.

Initialization won't help

Manually initializing the id field in your code won't impress your database if it insists on a default value. Like a careful dance, Hibernate and the database must agree on who leads the generation.

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