hibernate-upgrade

Hibernate 5 to 6 Upgrade Skill

Overview

Spring Boot 3 uses Hibernate 6, which includes significant changes from Hibernate 5. This skill covers the key migration considerations.

Key Changes

1. Package Namespace

Hibernate 6 uses Jakarta Persistence:

// Before (Hibernate 5)
import javax.persistence.*;
import org.hibernate.annotations.*;

// After (Hibernate 6)
import jakarta.persistence.*;
import org.hibernate.annotations.*;

2. ID Generation Strategies

Hibernate 6 changed the default ID generation strategy:

// Recommended approach for cross-database compatibility
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;

// Or using sequences (preferred for some databases)
@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "user_seq")
@SequenceGenerator(name = "user_seq", sequenceName = "user_sequence", allocationSize = 1)
private Long id;

3. Dialect Configuration

Hibernate 6 can auto-detect dialects in most cases:

# Before (often required in Hibernate 5)
spring.jpa.database-platform=org.hibernate.dialect.H2Dialect

# After (Hibernate 6) - often can be removed
# Hibernate auto-detects based on JDBC URL
# Only specify if you need specific behavior

If you must specify:

# Hibernate 6 dialects (some renamed)
spring.jpa.database-platform=org.hibernate.dialect.H2Dialect
spring.jpa.database-platform=org.hibernate.dialect.PostgreSQLDialect
spring.jpa.database-platform=org.hibernate.dialect.MySQLDialect

4. Query Changes

JPQL Changes

Some JPQL syntax has stricter validation:

// Be explicit about entity aliases
@Query("SELECT u FROM User u WHERE u.active = true")
List<User> findActiveUsers();

// Avoid implicit joins - be explicit
@Query("SELECT u FROM User u JOIN u.roles r WHERE r.name = :roleName")
List<User> findByRoleName(@Param("roleName") String roleName);

Native Queries

Native query result mapping changed:

// Before (Hibernate 5)
@Query(value = "SELECT * FROM users WHERE active = 1", nativeQuery = true)
List<User> findActiveUsersNative();

// After (Hibernate 6) - works the same, but be careful with projections
@Query(value = "SELECT * FROM users WHERE active = true", nativeQuery = true)
List<User> findActiveUsersNative();