Follow below step-by-step procedure to connect to H2 database using Hibernate.
Step 1: Create new maven project ‘hibernate-h2-hello-world’.
Step 2: Update pom.xml with maven dependencies.
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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.sample.app</groupId>
<artifactId>hibernate-h2-hello-world</artifactId>
<version>1</version>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<java.version>15</java.version>
<maven.compiler.source>${java.version}</maven.compiler.source>
<maven.compiler.target>${java.version}</maven.compiler.target>
</properties>
<dependencies>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<version>2.1.214</version>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
<version>6.1.2.Final</version>
</dependency>
<dependency>
<groupId>javax.persistence</groupId>
<artifactId>javax.persistence-api</artifactId>
<version>2.2</version>
</dependency>
</dependencies>
</project>
Step 3: Define Employee entity class.
Employee.java
package com.sample.app.entity;
import jakarta.persistence.Entity;
import jakarta.persistence.Id;
import jakarta.persistence.Table;
@Entity
@Table(name = "employees")
public class Employee {
@Id
private int id;
private String firstName;
private String lastName;
private String designation;
private int age;
public Employee() {
}
public Employee(int id, String firstName, String lastName, String designation, int age) {
super();
this.id = id;
this.firstName = firstName;
this.lastName = lastName;
this.designation = designation;
this.age = age;
}
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 getDesignation() {
return designation;
}
public void setDesignation(String designation) {
this.designation = designation;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return "Employee [id=" + id + ", firstName=" + firstName + ", lastName=" + lastName + ", designation="
+ designation + ", age=" + age + "]";
}
}
Step 4: Create hibernate.cfg.xml file under src/main/resources folder.
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>
<!-- JDBC Database connection settings -->
<property name="connection.driver_class">org.h2.Driver</property>
<property name="connection.url">jdbc:h2:mem:test</property>
<property name="connection.username">admin</property>
<property name="connection.password">admin</property>
<property name="connection.pool_size">1</property>
<property name="dialect">org.hibernate.dialect.H2Dialect</property>
<!-- Echo the SQL to stdout -->
<property name="show_sql">true</property>
<property name="format_sql">true</property>
<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">2</property>
<property name="hibernate.dbcp.maxTotal">10</property>
<property name="hibernate.dbcp.maxIdle">5</property>
<property name="hibernate.dbcp.minIdle">3</property>
<property name="hibernate.dbcp.maxWaitMillis">-1</property>
<!-- mappings for annotated classes -->
<mapping class="com.sample.app.entity.Employee" />
</session-factory>
</hibernate-configuration>
Step 5: Define main application class.
App.java
package com.sample.app;
import java.io.IOException;
import java.net.URISyntaxException;
import java.util.List;
import org.hibernate.Session;
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;
import com.sample.app.entity.Employee;
import jakarta.persistence.criteria.CriteriaBuilder;
import jakarta.persistence.criteria.CriteriaQuery;
public class App {
private static SessionFactory sessionFactory = buildSessionFactory();
private static <T> List<T> loadAllData(Class<T> clazz, Session session) {
final CriteriaBuilder builder = session.getCriteriaBuilder();
final CriteriaQuery<T> criteria = builder.createQuery(clazz);
criteria.from(clazz);
return session.createQuery(criteria).getResultList();
}
private static SessionFactory buildSessionFactory() {
try {
if (sessionFactory == null) {
StandardServiceRegistry standardRegistry = new StandardServiceRegistryBuilder()
.configure("hibernate.cfg.xml").build();
Metadata metaData = new MetadataSources(standardRegistry).getMetadataBuilder().build();
sessionFactory = metaData.getSessionFactoryBuilder().build();
}
return sessionFactory;
} catch (Throwable ex) {
throw new ExceptionInInitializerError(ex);
}
}
public static void main(String args[]) throws ClassNotFoundException, IOException, URISyntaxException {
Employee emp1 = new Employee(1, "Krishna", "G", "Senior Software Developer", 26);
Employee emp2 = new Employee(2, "Shreyas", "Desai", "Team Manager", 35);
Employee emp3 = new Employee(3, "Piyush", "Rai", "Senior Software Developer", 26);
Employee emp4 = new Employee(4, "Maruti", "Borker", "Software Developer", 26);
try (Session session = sessionFactory.openSession()) {
session.beginTransaction();
session.persist(emp1);
session.persist(emp2);
session.persist(emp3);
session.persist(emp4);
List<Employee> emps = loadAllData(Employee.class, session);
for (Employee emp : emps) {
System.out.println(emp);
}
session.getTransaction().commit();
}
}
}
Total project structure looks like below.
Run App.java, you will see below messages in the console.
Aug 17, 2022 7:57:46 PM org.hibernate.Version logVersion
INFO: HHH000412: Hibernate ORM core version 6.1.2.Final
Aug 17, 2022 7:57:46 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl configure
WARN: HHH10001002: Using built-in connection pool (not intended for production use)
Aug 17, 2022 7:57:46 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001005: Loaded JDBC driver class: org.h2.Driver
Aug 17, 2022 7:57:46 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001012: Connecting with JDBC URL [jdbc:h2:mem:test]
Aug 17, 2022 7:57:46 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001001: Connection properties: {password=****, user=admin}
Aug 17, 2022 7:57:46 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl buildCreator
INFO: HHH10001003: Autocommit mode: false
Aug 17, 2022 7:57:46 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl$PooledConnections <init>
INFO: HHH10001115: Connection pool size: 1 (min=1)
Aug 17, 2022 7:57:46 PM org.hibernate.engine.jdbc.dialect.internal.DialectFactoryImpl logSelectedDialect
INFO: HHH000400: Using dialect: org.hibernate.dialect.H2Dialect
Hibernate:
drop table if exists employees cascade
Aug 17, 2022 7:57:47 PM org.hibernate.resource.transaction.backend.jdbc.internal.DdlTransactionIsolatorNonJtaImpl getIsolatedConnection
INFO: HHH10001501: Connection obtained from JdbcConnectionAccess [org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator$ConnectionProviderJdbcConnectionAccess@3e5fd2b1] for (non-JTA) DDL execution was not in auto-commit mode; the Connection 'local transaction' will be committed and the Connection will be set into auto-commit mode.
Hibernate:
create table employees (
id integer not null,
age integer not null,
designation varchar(255),
firstName varchar(255),
lastName varchar(255),
primary key (id)
)
Aug 17, 2022 7:57:47 PM org.hibernate.resource.transaction.backend.jdbc.internal.DdlTransactionIsolatorNonJtaImpl getIsolatedConnection
INFO: HHH10001501: Connection obtained from JdbcConnectionAccess [org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator$ConnectionProviderJdbcConnectionAccess@23a918c7] for (non-JTA) DDL execution was not in auto-commit mode; the Connection 'local transaction' will be committed and the Connection will be set into auto-commit mode.
Hibernate:
insert
into
employees
(age, designation, firstName, lastName, id)
values
(?, ?, ?, ?, ?)
Hibernate:
insert
into
employees
(age, designation, firstName, lastName, id)
values
(?, ?, ?, ?, ?)
Hibernate:
insert
into
employees
(age, designation, firstName, lastName, id)
values
(?, ?, ?, ?, ?)
Hibernate:
insert
into
employees
(age, designation, firstName, lastName, id)
values
(?, ?, ?, ?, ?)
Hibernate:
select
e1_0.id,
e1_0.age,
e1_0.designation,
e1_0.firstName,
e1_0.lastName
from
employees e1_0
Employee [id=1, firstName=Krishna, lastName=G, designation=Senior Software Developer, age=26]
Employee [id=2, firstName=Shreyas, lastName=Desai, designation=Team Manager, age=35]
Employee [id=3, firstName=Piyush, lastName=Rai, designation=Senior Software Developer, age=26]
Employee [id=4, firstName=Maruti, lastName=Borker, designation=Software Developer, age=26]
You can download complete working application from this link.
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