Hibernate @CreationTimestamp and @UpdateTimestamp Tutorial

In this tutorial, we will create a simple example using Hibernate to demonstrate the use of @CreationTimestamp and @UpdateTimestamp annotations. These annotations are used to automatically populate timestamp fields for entity creation and updates.

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-timestamp-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>

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 @CreationTimestamp and @UpdateTimestamp

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

package com.example.entity;

import jakarta.persistence.*;
import org.hibernate.annotations.CreationTimestamp;
import org.hibernate.annotations.UpdateTimestamp;

import java.time.LocalDateTime;

@Entity
public class Message {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    private String text;

    @CreationTimestamp
    @Column(updatable = false)
    private LocalDateTime createdAt;

    @UpdateTimestamp
    private LocalDateTime updatedAt;

    public Message() {}

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

    public Long getId() {
        return id;
    }

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

    public String getText() {
        return text;
    }

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

    public LocalDateTime getCreatedAt() {
        return createdAt;
    }

    public LocalDateTime getUpdatedAt() {
        return updatedAt;
    }

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

Explanation of @CreationTimestamp and @UpdateTimestamp annotations

• @CreationTimestamp: This annotation marks a field to be automatically populated with the current timestamp when the entity is first persisted (saved) to the database. The @Column(updatable = false) annotation ensures that this value is not updated once it is set.

• @UpdateTimestamp: This annotation marks a field to be automatically populated with the current timestamp whenever the entity is updated.

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;

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, Timestamps!");
        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);

        // Update the message
        transaction = session.beginTransaction();
        retrievedMessage.setText("Hello, Updated Timestamps!");
        session.update(retrievedMessage);
        transaction.commit();

        // Retrieve the updated message
        Message updatedMessage = session.get(Message.class, retrievedMessage.getId());
        System.out.println("Updated Message: " + updatedMessage);

        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 bigint generated by default as identity, createdAt timestamp, text varchar(255), updatedAt timestamp, primary key (id))
Hibernate: insert into Message (createdAt, text, updatedAt) values (?, ?, ?)
Hibernate: select message0_.id as id1_0_0_, message0_.createdAt as createdA2_0_0_, message0_.text as text3_0_0_, message0_.updatedAt as updatedA4_0_0_ from Message message0_ where message0_.id=?
Retrieved Message: Message{id=1, text='Hello, Timestamps!', createdAt=2024-05-15T10:20:30, updatedAt=2024-05-15T10:20:30}
Hibernate: update Message set text=?, updatedAt=? where id=?
Hibernate: select message0_.id as id1_0_0_, message0_.createdAt as createdA2_0_0_, message0_.text as text3_0_0_, message0_.updatedAt as updatedA4_0_0_ from Message message0_ where message0_.id=?
Updated Message: Message{id=1, text='Hello, Updated Timestamps!', createdAt=2024-05-15T10:20:30, updatedAt=2024-05-15T10:25:30}

Conclusion

You have successfully created an example using Hibernate with @CreationTimestamp and @UpdateTimestamp annotations. This tutorial covered setting up a Maven project, configuring Hibernate, creating an entity class with timestamp fields, and performing basic CRUD operations to observe the automatic population of the timestamp fields.