How to Generate UUIDs as Primary Keys with Hibernate

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Using UUIDs (Universally Unique Identifiers) as primary keys in Hibernate ensures globally unique identifiers across distributed systems. In this tutorial, we will create a simple example using Hibernate 6 to generate UUIDs as primary keys.

Prerequisites

1. Java Development Kit (JDK) 21 or higher: Ensure JDK is installed and configured in your system.
2. Integrated Development Environment (IDE): IntelliJ IDEA, Eclipse, or any other IDE.
3. Maven: Ensure Maven is installed and configured in your system.

Step 1: Create a Maven Project

1. Open your IDE and create a new Maven project.
2. Update the pom.xml file to include Hibernate and other required dependencies.

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.example</groupId> <artifactId>hibernate-uuid-example</artifactId> <version>1.0-SNAPSHOT</version> <dependencies> <dependency> <groupId>org.hibernate.orm</groupId> <artifactId>hibernate-core</artifactId> <version>6.2.0.Final</version> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-api</artifactId> <version>1.7.30</version> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-simple</artifactId> <version>1.7.30</version> </dependency> <dependency> <groupId>com.h2database</groupId> <artifactId>h2</artifactId> <version>1.4.200</version> </dependency> </dependencies> </project> 

Explanation

• Hibernate Core Dependency: Includes the main Hibernate framework.
• SLF4J Dependencies: Used for logging.
• H2 Database Dependency: An in-memory database for testing purposes.

Step 2: Create Hibernate Configuration File

Create a file named hibernate.cfg.xml in the src/main/resources directory.

<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <property name="hibernate.dialect">org.hibernate.dialect.H2Dialect</property> <property name="hibernate.connection.driver_class">org.h2.Driver</property> <property name="hibernate.connection.url">jdbc:h2:mem:testdb</property> <property name="hibernate.connection.username">sa</property> <property name="hibernate.connection.password"></property> <property name="hibernate.hbm2ddl.auto">update</property> <property name="hibernate.show_sql">true</property> <property name="hibernate.format_sql">true</property> </session-factory> </hibernate-configuration> 

Explanation

• Dialect: Specifies the SQL dialect (H2 in this case).
• Connection Properties: Configure the JDBC connection to the H2 database.
• hbm2ddl.auto: Automatically manages the database schema (update existing schema).
• show_sql: Prints SQL statements to the console.
• format_sql: Formats SQL statements.

Step 3: Create the Employee Entity Class with UUID as the Primary Key

Create a package named com.example.entity and a class named Employee.

package com.example.entity; import jakarta.persistence.*; import java.util.UUID; @Entity public class Employee { @Id @GeneratedValue(strategy = GenerationType.UUID) private UUID id; private String name; private String department; public Employee() {} public Employee(String name, String department) { this.name = name; this.department = department; } public UUID getId() { return id; } public void setId(UUID id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getDepartment() { return department; } public void setDepartment(String department) { this.department = department; } @Override public String toString() { return "Employee{id=" + id + ", name='" + name + '\'' + ", department='" + department + '\'' + '}'; } } 

Explanation

• @Id: Marks the field as the primary key.
• @GeneratedValue: Specifies the strategy for generating values for the primary key.
• @GenericGenerator: Configures a custom generator (UUID generator in this case).

Step 4: Create Hibernate Utility Class

Create a package named com.example.util and a class named HibernateUtil.

package com.example.util; import org.hibernate.SessionFactory; import org.hibernate.boot.registry.StandardServiceRegistryBuilder; import org.hibernate.cfg.Configuration; import org.hibernate.service.ServiceRegistry; public class HibernateUtil { private static SessionFactory sessionFactory; static { try { Configuration configuration = new Configuration().configure(); ServiceRegistry serviceRegistry = new StandardServiceRegistryBuilder() .applySettings(configuration.getProperties()).build(); sessionFactory = configuration.buildSessionFactory(serviceRegistry); } catch (Throwable ex) { throw new ExceptionInInitializerError(ex); } } public static SessionFactory getSessionFactory() { return sessionFactory; } } 

Explanation

• Configuration: Loads Hibernate configuration from hibernate.cfg.xml.
• ServiceRegistry: Builds the service registry from the configuration settings.
• SessionFactory: Provides sessions to interact with the database.

Step 5: Create Main Class

Create a package named com.example and a class named Main.

package com.example; import com.example.entity.Employee; import com.example.util.HibernateUtil; import org.hibernate.Session; import org.hibernate.Transaction; import java.util.UUID; public class Main { public static void main(String[] args) { // Save a new employee Session session = HibernateUtil.getSessionFactory().openSession(); Transaction transaction = session.beginTransaction(); Employee employee = new Employee("John Doe", "IT"); session.save(employee); transaction.commit(); session.close(); // Retrieve the employee session = HibernateUtil.getSessionFactory().openSession(); Employee retrievedEmployee = session.get(Employee.class, employee.getId()); System.out.println("Retrieved Employee: " + retrievedEmployee); // Close the SessionFactory HibernateUtil.getSessionFactory().close(); } } 

Explanation

• Session: Opens a session to interact with the database.
• Transaction: Begins and commits a transaction for database operations.
• Save: Persists the entity to the database.
• Retrieve: Fetches the entity from the database using its UUID.

Step 6: Run the Application

1. Run the Main class.
2. The output in the console should be:

Hibernate: create table Employee (id binary(255) not null, department varchar(255), name varchar(255), primary key (id)) Hibernate: insert into Employee (id, department, name) values (?, ?, ?) Hibernate: select employee0_.id as id1_0_0_, employee0_.department as departme2_0_0_, employee0_.name as name3_0_0_ from Employee employee0_ where employee0_.id=? Retrieved Employee: Employee{id=<UUID>, name='John Doe', department='IT'} 

Conclusion

You have successfully created an example using Hibernate 6 to generate UUIDs as primary keys. This tutorial covered setting up a Maven project, configuring Hibernate, creating an entity class with a UUID primary key, and performing basic CRUD operations to observe the automatic generation and handling of UUIDs.