Hibernate with UUIDs as Primary Keys

Using UUIDs (Universally Unique Identifiers) as primary keys in Hibernate can be useful for ensuring globally unique identifiers across distributed systems. In this tutorial, we will create a simple example using Hibernate 6 with UUIDs as primary keys.

Prerequisites

1. Java Development Kit (JDK) 11 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>6.0.0.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>

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>

Step 3: Create an Entity Class with UUID

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

package com.example.entity;

import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.Id;
import org.hibernate.annotations.GenericGenerator;
import java.util.UUID;

@Entity
public class Message {
    @Id
    @GeneratedValue(generator = "UUID")
    @GenericGenerator(
        name = "UUID",
        strategy = "org.hibernate.id.UUIDGenerator"
    )
    private UUID id;
    private String text;

    public Message() {}

    public Message(String text) {
        this.text = text;
    }

    public UUID getId() {
        return id;
    }

    public void setId(UUID id) {
        this.id = id;
    }

    public String getText() {
        return text;
    }

    public void setText(String text) {
        this.text = text;
    }

    @Override
    public String toString() {
        return "Message{id=" + id + ", text='" + text + '\'' + '}';
    }
}

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;
    }
}

Step 5: Create Main Class

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

package com.example;

import com.example.entity.Message;
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 message
        Session session = HibernateUtil.getSessionFactory().openSession();
        Transaction transaction = session.beginTransaction();
        Message message = new Message("Hello, UUID!");
        session.save(message);
        transaction.commit();
        session.close();

        // Retrieve the message
        session = HibernateUtil.getSessionFactory().openSession();
        Message retrievedMessage = session.get(Message.class, message.getId());
        System.out.println("Retrieved Message: " + retrievedMessage);
        session.close();

        // Close the SessionFactory
        HibernateUtil.getSessionFactory().close();
    }
}

Step 6: Run the Application

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

Hibernate: create table Message (id binary(255) not null, text varchar(255), primary key (id))
Hibernate: insert into Message (id, text) values (?, ?)
Hibernate: select message0_.id as id1_0_0_, message0_.text as text2_0_0_ from Message message0_ where message0_.id=?
Retrieved Message: Message{id=<UUID>, text='Hello, UUID!'}

Conclusion

You have successfully created an example using Hibernate 6 with 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.