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Hibernate Example Using Spring Boot
Hibernate is an Object Relational Mapping (ORM) framework for mapping Java objects to relational database tables and vice versa. Spring Boot is a framework for building production-ready applications with minimal configuration and setup. When used together, Hibernate and Spring Boot provide a powerful and flexible platform for developing database-backed applications.
Spring Boot provides support for integrating Hibernate into a Spring Boot application through the Spring Data JPA (Java Persistence API) module. This module provides a simple and straightforward way of accessing and managing data in a relational database using Hibernate. It eliminates the need for manual configuration of Hibernate and automatically creates the required beans and schema for accessing data from a database.
Here is an example of how to use Hibernate in a Spring Boot application:
Below is the structure of the project we are going to create for this example
1. Go to Spring initializr website and create a Java Maven Project with JPA and H2 dependency. Hibernate is used as default implementation for JPA in Spring Boot. Use Generate button to download the project and open in your IDE.
Below is the generated pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<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>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.7.3</version>
<relativePath/> <!-- lookup parent from repository -->
</parent>
<groupId>com.example</groupId>
<artifactId>demo</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>demo</name>
<description>Demo project for Spring Boot</description>
<properties>
<java.version>11</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
2. Create Entity classes Employee.java and Department.java in entities package
package net.itcodescanner.entities;
import javax.persistence.*;
@Entity
public class Employee {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private int id;
private String name;
private String address;
@ManyToOne
@JoinColumn(foreignKey = @ForeignKey(name = "fk_employee_department"))
private Department department;
public Employee() {
}
public Employee( String name, String address, Department department) {
this.name = name;
this.address = address;
this.department = department;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
public Department getDepartment() {
return department;
}
public void setDepartment(Department department) {
this.department = department;
}
}
package net.itcodescanner.entities;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
@Entity
public class Department {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String name;
public Department() {
}
public Department(String name) {
this.name = name;
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
3.Create Dao classes EmployeeDao and DepartmentDao extending CrudRepository. You can also add methods for custom queries. Such as to getByName. Or use @Query annotation to write custom query.
package com.example.demo.dao;
import com.example.demo.entities.Employee;
import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Repository;
@Repository
public interface EmployeeDao extends CrudRepository<Employee, Long> {}
package com.example.demo.dao;
import com.example.demo.entities.Department;
import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Repository;
@Repository
public interface DepartmentDao extends CrudRepository<Department, Long> {}
5. Create service DataProcessingService to call the database update methods:
package com.example.demo.service;
import com.example.demo.dao.DepartmentDao;
import com.example.demo.dao.EmployeeDao;
import com.example.demo.entities.Department;
import com.example.demo.entities.Employee;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
@Service
public class DataProcessingService {
@Autowired
private EmployeeDao employeeDao;
@Autowired
private DepartmentDao departmentDao;
public void insertData(){
Department d1 = new Department("Department-21");
Department d2 = new Department("Department-22");
departmentDao.save(d1);
departmentDao.save(d2);
Employee e1 = new Employee("EmpName-1", "Address-32", d1);
Employee e2 = new Employee("EmpName-2", "Address-54", d2);
employeeDao.save(e1);
employeeDao.save(e2);
}
public void printData(){
System.out.println("Employees");
employeeDao.findAll().forEach(employee -> System.out.println(employee.getId() +", " + employee.getName() + ", " + employee.getAddress() + ", " + employee.getDepartment().getName() ));
System.out.println("Departments");
departmentDao.findAll().forEach(department -> System.out.println(department.getName() + ", " + department.getId()));
}
}
6. Create the main SpringBootApplication class with @EnableTransactionManagement annotation. @EnableTransactionManagement annotation on the main class takes care of transactions. We do not need to write the code to get the session.
To call the service, CommandLineRunner interface is used. run method of this interface is executed immediately after the application startup.
package com.example.demo;
import com.example.demo.service.DataProcessingService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.transaction.annotation.EnableTransactionManagement;
@EnableTransactionManagement
@SpringBootApplication
public class DemoApplication implements CommandLineRunner {
@Autowired
private DataProcessingService s;
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
private void doDB(){
s.insertData();
s.printData();
}
@Override
public void run(String... args) throws Exception {
s.insertData();
s.printData();
}
}
Output:
Hibernate: drop table Department if exists Hibernate: drop table Employee if exists Hibernate: drop sequence if exists hibernate_sequence Aug 28, 2022 7:42:15 PM org.hibernate.resource.transaction.backend.jdbc.internal.DdlTransactionIsolatorNonJtaImpl getIsolatedConnection INFO: HHH10001501: Connection obtained from JdbcConnectionAccess [org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator$ConnectionProviderJdbcConnectionAccess@68ed96ca] for (non-JTA) DDL execution was not in auto-commit mode; the Connection 'local transaction' will be committed and the Connection will be set into auto-commit mode. Hibernate: create sequence hibernate_sequence start with 1 increment by 1 Hibernate: create table Department (id bigint not null, name varchar(255), primary key (id)) Hibernate: create table Employee (id integer not null, address varchar(255), name varchar(255), department_id bigint, primary key (id)) Hibernate: alter table Employee add constraint fk_employee_department foreign key (department_id) references Department Aug 28, 2022 7:42:15 PM org.hibernate.resource.transaction.backend.jdbc.internal.DdlTransactionIsolatorNonJtaImpl getIsolatedConnection INFO: HHH10001501: Connection obtained from JdbcConnectionAccess [org.hibernate.engine.jdbc.env.internal.JdbcEnvironmentInitiator$ConnectionProviderJdbcConnectionAccess@51b01960] 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. Aug 28, 2022 7:42:15 PM org.hibernate.tool.schema.internal.SchemaCreatorImpl applyImportSources INFO: HHH000476: Executing import script 'org.hibernate.tool.schema.internal.exec.ScriptSourceInputNonExistentImpl@4acf72b6' Hibernate: call next value for hibernate_sequence Hibernate: call next value for hibernate_sequence Hibernate: call next value for hibernate_sequence Hibernate: call next value for hibernate_sequence Hibernate: insert into Department (name, id) values (?, ?) Hibernate: insert into Department (name, id) values (?, ?) Hibernate: insert into Employee (address, department_id, name, id) values (?, ?, ?, ?) Hibernate: insert into Employee (address, department_id, name, id) values (?, ?, ?, ?) Employees Aug 28, 2022 7:42:16 PM org.hibernate.hql.internal.QueryTranslatorFactoryInitiator initiateService INFO: HHH000397: Using ASTQueryTranslatorFactory Hibernate: select employee0_.id as id1_1_, employee0_.address as address2_1_, employee0_.department_id as departme4_1_, employee0_.name as name3_1_ from Employee employee0_ Hibernate: select department0_.id as id1_0_0_, department0_.name as name2_0_0_ from Department department0_ where department0_.id=? Hibernate: select department0_.id as id1_0_0_, department0_.name as name2_0_0_ from Department department0_ where department0_.id=? 3, EmpName-1, Address-32, Department-21 4, EmpName-2, Address-54, Department-22 Departments Hibernate: select department0_.id as id1_0_, department0_.name as name2_0_ from Department department0_ Department-21, 1 Department-22, 2 Aug 28, 2022 7:42:16 PM org.hibernate.engine.jdbc.connections.internal.DriverManagerConnectionProviderImpl stop INFO: HHH10001008: Cleaning up connection pool [jdbc:h2:./data/db] Process finished with exit code 0
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