This tutorial is a part of the Hibernate introduction series and is useful in getting started with the Hibernate. We used JDK, Eclipse IDE and Maven build tool. This quick guide will show you how to use Maven to generate a simple Java project, and uses Hibernate to insert a record into the MySQL database.
 
 
 
 
 
 
 

1. Introduction

1.1 Hibernate

• Object-Relational Mapping or ORM is the programming technique to map application domain model objects to the relational database tables
• Hibernate is Java-based ORM tool that provides the framework for mapping application domain objects to the relational database tables and vice versa. It provides reference implementation of Java Persistence API, that makes it a great choice as an ORM tool with benefits of loose coupling
• Framework provides option to map plain old Java objects to traditional database tables with the use of JPA annotations as well as XML based configuration

1.2 Hibernate Architecture

There are 4 layers in the Hibernate architecture i.e. Java Application Layer, Hibernate Framework Layer, Backend API Layer, and the Database Layer. Let’s understand the diagram of Hibernate architecture.

For creating the first Hibernate application, we must know the elements of the Hibernate architecture. They are as follows:

1.3 Hibernate Benefits

There are many advantages of using the Hibernate framework, for e.g.

• • Hibernate framework is open-source and lightweight
  • The performance of Hibernate framework is fast and supports smart fetching techniques because of the internal caching mechanism
  • Hibernate framework provides the facility to create the database tables automatically
  • With the help ofHQL (Hibernate Query Language), the generatedSQL queries are independent of databases
  • Provides query facilities to fetch the data from multiple databases, and supports transaction management and automatic key generations
  • Provides APIs for storing and retrieving the Java objects directly to and from the database
  • Framework takes care of the mapping Java classes to database tables using XML files or annotations

1.4 Maven

Apache Maven is one of the most popular Software project management and comprehension tool, based on a central piece of information calledProject Object Model (POM). Project-based on Maven gets its compilation, build, reporting and documentation instructions from an XML file namedpom.xml.

pom.xml is a standardXML file complying Maven scheme. It contains the dependencies required by the project, the plugins that the project might need, the repository that the project can look into to search for the dependencies, the parent/child module information in case of multi-module projects, the profile to support different builds for different situations/environments and many more features.

1.4.1 Ant vs. Maven

Ant and Maven both are build tools provided by Apache. The main purpose of these technologies is to ease the build process of a project. There are many differences between Ant and Maven and they are given below:

1.5 Download and Install Hibernate

You can readthis tutorial in order to download and install Hibernate in the Eclipse IDE.

1.6 Download and Install MySQL

You can watchthis video in order to download and install the MySQL database on your Windows operating system.

1.7 Download and Install Maven

You can readthis tutorial in order to download and install Maven on your Windows operating system.

Now, open up the Eclipse IDE and let’s see how to implement Maven!

2. Hibernate Maven Example

2.1 Tools Used

We are using Eclipse Kepler SR2, JDK 8, MySQL Database and Maven. Having said that, we have tested the code against JDK 1.7 and it works well.

2.2 Project Structure

2.3 Project Creation

This section will demonstrate on how to create a Java-based Maven project with Eclipse. In Eclipse IDE, go toFile -> New -> Maven Project.

In the New Maven Project window, it will ask you to select project location. By default, ‘Use default workspace location‘ will be selected. Select the ‘Create a simple project (skip archetype selection)‘ checkbox and just click on next button to proceed.

It will ask you to ‘Enter the group and the artifact id for the project’. We will input the details as shown in the below image. The version number will be by default0.0.1-SNAPSHOT.

Click on Finish and the creation of a maven project is completed. If you observe, it has downloaded the maven dependencies and apom.xml file will be created. It will have the following code:

pom.xml

<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>HibernateMaven</groupId><artifactId>HibernateMaven</artifactId><version>0.0.1-SNAPSHOT</version><packaging>jar</packaging></project>

We can start adding the dependencies that developers want like Hibernate, MySQL etc. Let’s start building the application!

3. Application Building

Below are the steps involved in developing this application.

3.1 Database & Table Creation

The following MySQL script is used to create a database calledtutorialDb with table:user_table. Open MySQL terminal or workbench terminal and execute the script.

CREATE DATABASE IF NOT EXISTS tutorialDb;USE tutorialDb;DROP TABLE IF EXISTS user_table;CREATE TABLE user_table (  user_id int(20) NOT NULL,  user_name varchar(255) NULL,  created_by VARCHAR (255) NOT NULL,  created_date DATE NOT NULL,  PRIMARY KEY (user_id));

If everything goes well, the table will be shown in the MySQL workbench.

3.2 Maven Dependencies

Here, we specify only two dependencies for Hibernate Core and MySQL Connector. Rest dependencies will be automatically resolved by Maven, such as Hibernate JPA and Hibernate Commons Annotations. Theupdated file will have the following code:

pom.xml

<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>HibernateMaven</groupId><artifactId>HibernateMaven</artifactId><version>0.0.1-SNAPSHOT</version><dependencies><!-- Hibernate 4.3.6 Final --><dependency><groupId>org.hibernate</groupId><artifactId>hibernate-core</artifactId><version>4.3.6.Final</version></dependency><!-- Mysql Connector --><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>5.1.21</version></dependency></dependencies><build><finalName>${project.artifactId}</finalName></build></project>

Maven will download all Hibernate and MySQL libraries automatically and it will put them into Maven’s local repository. At the same time, Maven will add the downloaded libraries into Eclipse.classpath file for dependency purpose.

3.3 Java Class Creation

Let’s create the required Java files. Right-click onsrc/main/java folder,New -> Package.

A new pop window will open where we will enter the package name as:com.jcg.hibernate.maven.

Once the package is created in the application, we will need to create the model and implementation classes. Right-click on the newly created package:New -> Class.

A new pop window will open and enter the file name asUser. The model class will be created inside the package:com.jcg.hibernate.maven.

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Repeat the step (i.e. Fig. 9) and enter the filename asAppMain. The implementation class will be created inside the package:com.jcg.hibernate.batch.processing.

3.3.1 Implementation of Model Class

Consider the followingPOJO class and add the following code to it:

User.java

package com.jcg.hibernate.maven;import java.util.Date;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.Id;import javax.persistence.Table;@Entity@Table(name = "user_table")public class User {@Id@Column(name = "user_id")private int userid;@Column(name = "user_name")private String username;@Column(name = "created_by")private String createdBy;@Column(name = "created_date")private Date createdDate;public int getUserid() {return userid;}public void setUserid(int userid) {this.userid = userid;}public String getUsername() {return username;}public void setUsername(String username) {this.username = username;}public String getCreatedBy() {return createdBy;}public void setCreatedBy(String createdBy) {this.createdBy = createdBy;}public Date getCreatedDate() {return createdDate;}public void setCreatedDate(Date createdDate) {this.createdDate = createdDate;}}

3.3.2 Implementation of Utility Class

This class helps in creating theSessionFactory from the Hibernate configuration file and interacts with the database to perform the Hibernate operation. Add the following code to it:

AppMain.java

package com.jcg.hibernate.maven;import java.util.Date;import org.hibernate.Session;import org.hibernate.SessionFactory;import org.hibernate.boot.registry.StandardServiceRegistryBuilder;import org.hibernate.cfg.Configuration;import org.hibernate.service.ServiceRegistry;public class AppMain {static User userObj;static Session sessionObj;static SessionFactory sessionFactoryObj;private static SessionFactory buildSessionFactory() {// Creating Configuration Instance & Passing Hibernate Configuration FileConfiguration configObj = new Configuration();configObj.configure("hibernate.cfg.xml");// Since Hibernate Version 4.x, ServiceRegistry Is Being UsedServiceRegistry serviceRegistryObj = new StandardServiceRegistryBuilder().applySettings(configObj.getProperties()).build(); // Creating Hibernate SessionFactory InstancesessionFactoryObj = configObj.buildSessionFactory(serviceRegistryObj);return sessionFactoryObj;}public static void main(String[] args) {System.out.println(".......Hibernate Maven Example.......\n");try {sessionObj = buildSessionFactory().openSession();sessionObj.beginTransaction();for(int i = 101; i <= 105; i++) {userObj = new User();userObj.setUserid(i);userObj.setUsername("Editor " + i);userObj.setCreatedBy("Administrator");userObj.setCreatedDate(new Date());sessionObj.save(userObj);}System.out.println("\n.......Records Saved Successfully To The Database.......\n");// Committing The Transactions To The DatabasesessionObj.getTransaction().commit();} catch(Exception sqlException) {if(null != sessionObj.getTransaction()) {System.out.println("\n.......Transaction Is Being Rolled Back.......");sessionObj.getTransaction().rollback();}sqlException.printStackTrace();} finally {if(sessionObj != null) {sessionObj.close();}}}}

3.4. Hibernate Configuration File

To configure the Hibernate framework, we need to implement a configuration file i.e.hiberncate.cfg.xml. Right click onsrc/main/resources folder,New -> Other.

A new pop window will open and select the wizard as an XML file.

Again, a pop-up window will open. Verify the parent folder location asHibernateMaven/src/main/resources and enter the file name ashibernate.cfg.xml. Click Finish.

Once the file is created, we will include the database configuration and mapping classes details. Add the following code to it:

hibernate.cfg.xml

<?xml version='1.0' encoding='UTF-8'?><!DOCTYPE hibernate-configuration PUBLIC        "-//Hibernate/Hibernate Configuration DTD 3.0//EN"        "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd"><hibernate-configuration><session-factory><!-- SQL Dialect --><property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property><!-- Database Connection Settings --><property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property><property name="hibernate.connection.url">jdbc:mysql://localhost:3306/tutorialDb</property><property name="hibernate.connection.username">root</property><property name="hibernate.connection.password"></property><property name="show_sql">true</property><!-- Specifying Session Context --><property name="hibernate.current_session_context_class">org.hibernate.context.internal.ThreadLocalSessionContext</property><!-- Mapping With Model Class Containing Annotations --><mapping /></session-factory></hibernate-configuration>

Notes:

• Here, we instructed Hibernate to connect to a MySQL database namedtutorialDb and the Mapping classes to be loaded
• We have also instructed Hibernate framework to useMySQLDialect i.e. Hibernate will optimize the generated SQL statements for MySQL
• This configuration will be used to create a HibernateSessionFactory object
• show_sql: This tag will instruct the Hibernate framework to log all theSQL statements on the console

4. Run the Application

To run the Hibernate application, Right click on theAppMain class-> Run As -> Java Application.

5. Project Demo

Executing theAppMain class, you will see the records inuser_table table. Developers can debug the example and see what happens in the database after every step. Enjoy!

Below is a snapshot of the MySQL Database after the execution of the above program.

User Table

That’s all for this post. Happy Learning!!

6. Conclusion

Hibernate is very useful, it takes plenty of work on itself. The main aim of Hibernate is to make development more easy and convenient. With Maven a basic shell project is ready for Hibernate based development. That’s all for Hibernate Maven tutorial and I hope this article served you whatever you were looking for.

7. Download the Eclipse Project

This was an example of Hibernate Maven.

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