Hibernate 6: H2 Hello world application

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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