Hibernate Framework Architecture and Basics
Hibernate Hello World Tutorial
Hibernate XML Configuration Example
Hibernate Java Configuration Example
Hibernate Transaction Management
Hibernate/JPA - Primary Key Generation Strategies
JPA and Hibernate Cascade Types
Hibernate - Save an Entity Example
Hibernate - Persist an Entity Example
Hibernate - saveOrUpdate() Method Example
Hibernate - get(), load() and byId() Method
Hibernate - merge() Example
Hibernate - Delete or Remove an Entity Example
Hibernate - load() Method Example
Hibernate Session.clear() Method Example
Hibernate One to One Mapping
Hibernate One to Many Mapping
Hibernate Many to Many Annotation
Hibernate One to Many CRUD Example
Hibernate One to One CRUD Example
Hibernate Inheritance Mapping
Hibernate Query Language
Hibernate CRUD Operations Example
Hibernate Session Interface Methods
JSP Servlet Hibernate CRUD Example
Hibernate Registration Form Example
Login Form using JSP + Servlet + Hibernate + MySQL
More .........
In this article, we will create a simple Hibernate application to demonstrate how to save an entity into a database. We are going to use the MySQL database to save the data.
We use Session save() method to save or persist an entity in the database.
Below diagram shows the snippet of saving an entity in a database:
Let's start developing step by step Hibernate application using Maven as project management and build tool.
Technologies and tools used
- Hibernate 5.3.7.Final
- IDE - Eclipse Noen
- Maven 3.5.3
- JavaSE 1.8
- MySQL - 8.0.13
Development Steps
- Create a Simple Maven Project
- Project Directory Structure
- Add jar Dependencies to pom.xml
- Creating the JPA Entity Class(Persistent class)
- Create a Hibernate configuration file - hibernate.cfg.xml
- Create a Hibernate utility class
- Create the Main class and Run an Application
1. Create a Simple Maven Project
Use the How to Create a Simple Maven Project in Eclipse article to create a simple Maven project in Eclipse IDE.
2. Project Directory Structure
The project directory structure for your reference -
3. Add jar Dependencies to pom.xml
Next, let's add the required dependencies to the pom.xml file:
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.13</version> </dependency> <!-- https://mvnrepository.com/artifact/org.hibernate/hibernate-core --> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-core</artifactId> <version>5.3.7.Final</version> </dependency>
Here is the complete pom.xml file for your reference:
<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>
<parent>
<groupId>net.javaguides.hibernate</groupId>
<artifactId>hibernate-tutorial</artifactId>
<version>0.0.1-SNAPSHOT</version>
</parent>
<artifactId>hibernate-xml-config-example</artifactId>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>
<dependencies>
<!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java -->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>8.0.13</version>
</dependency>
<!-- https://mvnrepository.com/artifact/org.hibernate/hibernate-core -->
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>5.3.7.Final</version>
</dependency>
</dependencies>
<build>
<sourceDirectory>src/main/java</sourceDirectory>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.5.1</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
</plugins>
</build>
</project>
4. Creating the JPA Entity Class(Persistent class)
Let's create a Student persistent class that is mapped to a database table.
Follow below some rules to create a valid JPA entity class:
- A no-arg constructor: It is recommended that you have a default constructor with at least package visibility so that hibernate can create the instance of the JPA entity class by newInstance() method.
- Provide an identifier property: It is better to assign an attribute as an id. This attribute behaves as a primary key in a database.
- Declare getter and setter methods: The Hibernate recognizes the method by getter and setter method names by default.
- Prefer non-final class: Hibernate uses the concept of proxies, which depends on the JPA entity class. The application programmer will not be able to use proxies for lazy association fetching.
Let's create a Student entity class under net.javaguides.hibernate.entity package as follows.
package net.javaguides.hibernate.entity;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;
@Entity
@Table(name = "student")
public class Student {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id")
private int id;
@Column(name = "first_name")
private String firstName;
@Column(name = "last_name")
private String lastName;
@Column(name = "email")
private String email;
public Student() {
}
public Student(String firstName, String lastName, String email) {
this.firstName = firstName;
this.lastName = lastName;
this.email = email;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getEmail() {
return email;
}
public void setEmail(String email) {
this.email = email;
}
@Override
public String toString() {
return "Student [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + ", email=" + email + "]";
}
}
JPA annotations that we are using in the Student entity:
@Entity - This annotation specifies that the class is an entity.
@Table - This annotation specifies the table in the database with which this entity is mapped.
@Column - The @Column annotation is used to specify the mapping between a basic entity attribute and the database table column.
@Id - This annotation specifies the primary key of the entity
@GeneratedValue - This annotation specifies the generation strategies for the values of primary keys.
Create a Hibernate Configuration file - hibernate.cfg.xml
The configuration file contains information about the database and mapping file. Conventionally, its name should be hibernate.cfg.xml.
You can use Hibernate 5 Java Configuration Example instead of a hibernate.cfg.xml file.
Let's create an XML file named hibernate.cfg.xml under the resources folder and write the following code in it.
<!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>
<!-- JDBC Database connection settings -->
<property name="connection.driver_class">com.mysql.cj.jdbc.Driver</property>
<property name="connection.url">jdbc:mysql://localhost:3306/hibernate_db?useSSL=false</property>
<property name="connection.username">root</property>
<property name="connection.password">root</property>
<!-- JDBC connection pool settings ... using built-in test pool -->
<property name="connection.pool_size">1</property>
<!-- Select our SQL dialect -->
<property name="dialect">org.hibernate.dialect.MySQL5Dialect</property>
<!-- Echo the SQL to stdout -->
<property name="show_sql">true</property>
<!-- Set the current session context -->
<property name="current_session_context_class">thread</property>
<!-- Drop and re-create the database schema on startup -->
<property name="hbm2ddl.auto">create-drop</property>
<!-- dbcp connection pool configuration -->
<property name="hibernate.dbcp.initialSize">5</property>
<property name="hibernate.dbcp.maxTotal">20</property>
<property name="hibernate.dbcp.maxIdle">10</property>
<property name="hibernate.dbcp.minIdle">5</property>
<property name="hibernate.dbcp.maxWaitMillis">-1</property>
<mapping class="net.javaguides.hibernate.entity.Student" />
</session-factory>
</hibernate-configuration>
6. Create a Hibernate utility Class
Create a helper class to bootstrap hibernate SessionFactory. In most Hibernate applications, the SessionFactory should be instantiated once during application initialization. The single instance should then be used by all code in a particular process, and any Session should be created using this single SessionFactory. The SessionFactory is thread-safe and can be shared.
Let's create HibernateUtil.java class to configure SessionFactory as a singleton and use it throughout the application.
The bootstrapping API is quite flexible, but in most cases, it makes the most sense to think of it as a 3 step process:
- Build the StandardServiceRegistry
- Build the Metadata
- Use those 2 to build the SessionFactory
package net.javaguides.hibernate.util;
import org.hibernate.SessionFactory;
import org.hibernate.boot.Metadata;
import org.hibernate.boot.MetadataSources;
import org.hibernate.boot.registry.StandardServiceRegistry;
import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
public class HibernateUtil {
private static StandardServiceRegistry registry;
private static SessionFactory sessionFactory;
public static SessionFactory getSessionFactory() {
if (sessionFactory == null) {
try {
// Create registry
registry = new StandardServiceRegistryBuilder().configure().build();
// Create MetadataSources
MetadataSources sources = new MetadataSources(registry);
// Create Metadata
Metadata metadata = sources.getMetadataBuilder().build();
// Create SessionFactory
sessionFactory = metadata.getSessionFactoryBuilder().build();
} catch (Exception e) {
e.printStackTrace();
if (registry != null) {
StandardServiceRegistryBuilder.destroy(registry);
}
}
}
return sessionFactory;
}
public static void shutdown() {
if (registry != null) {
StandardServiceRegistryBuilder.destroy(registry);
}
}
}
7. Create the main App class and Run an Application
Here is the main App class which is used to connect the MySQL database and persist Student object in a database table.
Let's test Hibernate application to connect MySQL database.
package net.javaguides.hibernate;
import java.util.List;
import org.hibernate.Session;
import org.hibernate.Transaction;
import net.javaguides.hibernate.entity.Student;
import net.javaguides.hibernate.util.HibernateUtil;
public class App {
public static void main(String[] args) {
Student student = new Student("Ramesh", "Fadatare", "rameshfadatare@javaguides.com");
Student student1 = new Student("John", "Cena", "john@javaguides.com");
Transaction transaction = null;
try (Session session = HibernateUtil.getSessionFactory().openSession()) {
// start a transaction
transaction = session.beginTransaction();
// save the student objects
session.save(student);
session.save(student1);
// commit transaction
transaction.commit();
} catch (Exception e) {
if (transaction != null) {
transaction.rollback();
}
e.printStackTrace();
}
try (Session session = HibernateUtil.getSessionFactory().openSession()) {
List < Student > students = session.createQuery("from Student", Student.class).list();
students.forEach(s - > System.out.println(s.getFirstName()));
} catch (Exception e) {
if (transaction != null) {
transaction.rollback();
}
e.printStackTrace();
}
}
}
Output
GitHub Repository
The complete source code of this article is available on my GitHub Repository - https://github.com/RameshMF/Hibernate-ORM-Tutorials
Conclusion
In this article, we have created a step-by-step hibernate application to demonstrate how to save a JPA entity into a database using a session.save() method.
You can learn more about Hibernate ORM Framework at Hibernate Tutorial
References
Free Spring Boot Tutorial | Full In-depth Course | Learn Spring Boot in 10 Hours
Watch this course on YouTube at Spring Boot Tutorial | Fee 10 Hours Full Course
Comments
Post a Comment