Spring Boot – H2 Database

H2 Database in Spring Boot is an embedded, open-source, and in-memory database. It is a relational database management system written in Java. It is a client/server application. It stores data in memory, not persist the data on disk. Here we will be discussing how can we configure and perform some basic operations in Spring Boot using H2 Database.

Features of the H2 Database:

• Very fast, open-source, JDBC API
• Embedded and server modes; disk-based or in-memory databases.
• Transaction support, multi-version concurrency
• Browser-based Console application
• Encrypted databases
• Fulltext search
• Pure Java with a small footprint: around 2.5 MB jar file size
• ODBC driver

Configure H2 Database in Spring Boot Application

Step 1: Adding the dependency

To use the H2 database in the spring boot application we have to add the following dependency in the pom.xml file:

h2 and spring-boot-starter-data-jpa 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>

Step 2: Write some properties in the application.properties file

# H2 Database
spring.h2.console.enabled=true
spring.datasource.url=jdbc:h2:mem:dcbapp
spring.datasource.driverClassName=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=password
spring.jpa.database-platform=org.hibernate.dialect.H2Dialect

We can also use YAML file for database configuration by adding properties to application.yml file as depicted below:

spring:
    h2:
         console.enabled: true
    datasource:
         url: jdbc:h2:mem:dcbapp
         driverClassName: org.h2.Driver
         username: sa
         password: password
     jpa: 
         spring.jpa.database-platform: org.hibernate.dialect.H2Dialect

Let’s understand what these properties are by opening the H2 Database console. 

H2 Console: By default, the console view of the H2 database is disabled. Before accessing the H2 database, we must enable it by using the following property:

spring.h2.console.enabled=true

Once we have enabled the H2 console, now we can access the H2 console in the browser by invoking the URL http://localhost:8082/h2-console. 

Note: Provide your port number in which your spring application is running

The following figure shows the console view of the H2 database.

Database Operation (CRUD Operation)

We are going to perform some basic CRUD Operations by creating a Spring Boot Application and using the H2 Database.

Steps to perform CRUD Operation using H2 database:

Step 1: Refer to this article How to Create a Spring Boot Project with IntelliJ IDEA and create a Spring Boot project. 

Step 2: Add the following dependency

• Spring Web
• H2 Database
• Lombok
• Spring Data JPA

Below is the complete code for the pom.xml file. Please check if you have missed something.

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>2.5.5</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.amiya</groupId>
    <artifactId>Spring-Boot-Demo-Project</artifactId>
    <version>1.0.0-SNAPSHOT</version>
    <name>Spring-Boot-Demo-Project</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-web</artifactId>
        </dependency>

        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <scope>runtime</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
            <scope>runtime</scope>
            <optional>true</optional>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <configuration>
                    <excludes>
                        <exclude>
                            <groupId>org.projectlombok</groupId>
                            <artifactId>lombok</artifactId>
                        </exclude>
                    </excludes>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>

Step 3: Create 4 packages and later create some classes and interfaces inside these packages as seen in the below image 

• entity
• repository
• service
• controller

Note:

• Green Rounded Icon ‘I’ Buttons are Interface.
• Blue Rounded Icon ‘C’ Buttons are Classes.

Step 4: Inside the entity package

Create a simple POJO class inside the Department.java file. 

Example:

Java

// Java Program to Demonstrate Department File

// Importing required package modules
package com.amiya.springbootdemoproject.entity;

// Importing required classes
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;

@Entity
@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder

// Class
public class Department {

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long departmentId;
    private String departmentName;
    private String departmentAddress;
    private String departmentCode;
}

Step 5: Inside the repository package

Create a simple interface and name the interface as DepartmentRepository. This interface is going to extend the CrudRepository as we have discussed above.

Example Below is the code for the DepartmentRepository.java file 

Java

package com.amiya.springbootdemoproject.repository;

import com.amiya.springbootdemoproject.entity.Department;
import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Repository;

// Annotation
@Repository

// Interface extending CrudRepository
public interface DepartmentRepository
    extends CrudRepository<Department, Long> {
}

Step 6: Inside the service package

Inside the package create one interface named as DepartmentService and one class named as DepartmentServiceImpl. 

Example 1-A

Java

// Java Program to Demonstrate DepartmentService File

// Importing required package modules
package com.amiya.springbootdemoproject.service;
import com.amiya.springbootdemoproject.entity.Department;
// Importing required classes
import java.util.List;

// Interface
public interface DepartmentService {

    // Save operation
    Department saveDepartment(Department department);

    // Read operation
    List<Department> fetchDepartmentList();

    // Update operation
    Department updateDepartment(Department department,
                                Long departmentId);

    // Delete operation
    void deleteDepartmentById(Long departmentId);
}

Example 1-B

Java

// Java Program to Demonstrate DepartmentServiceImpl.java
// File

// Importing required package modules
package com.amiya.springbootdemoproject.service;

import com.amiya.springbootdemoproject.entity.Department;
import com.amiya.springbootdemoproject.repository.DepartmentRepository;
import java.util.List;
import java.util.Objects;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

// Annotation
@Service

// Class
public class DepartmentServiceImpl
    implements DepartmentService {

    @Autowired
    private DepartmentRepository departmentRepository;

    // Save operation
    @Override
    public Department saveDepartment(Department department)
    {
        return departmentRepository.save(department);
    }

    // Read operation
    @Override public List<Department> fetchDepartmentList()
    {
        return (List<Department>)
            departmentRepository.findAll();
    }

    // Update operation
    @Override
    public Department
    updateDepartment(Department department,
                     Long departmentId)
    {
        Department depDB
            = departmentRepository.findById(departmentId)
                  .get();

        if (Objects.nonNull(department.getDepartmentName())
            && !"".equalsIgnoreCase(
                department.getDepartmentName())) {
            depDB.setDepartmentName(
                department.getDepartmentName());
        }

        if (Objects.nonNull(
                department.getDepartmentAddress())
            && !"".equalsIgnoreCase(
                department.getDepartmentAddress())) {
            depDB.setDepartmentAddress(
                department.getDepartmentAddress());
        }

        if (Objects.nonNull(department.getDepartmentCode())
            && !"".equalsIgnoreCase(
                department.getDepartmentCode())) {
            depDB.setDepartmentCode(
                department.getDepartmentCode());
        }

        return departmentRepository.save(depDB);
    }

    // Delete operation
    @Override
    public void deleteDepartmentById(Long departmentId)
    {
        departmentRepository.deleteById(departmentId);
    }
}

Step 7: Inside the controller package

Inside the package create one class named as DepartmentController. 

Example

Java

// java Program to Illustrate DepartmentController File

// Importing required packages modules
package com.amiya.springbootdemoproject.controller;

import com.amiya.springbootdemoproject.entity.Department;
import com.amiya.springbootdemoproject.service.DepartmentService;
import java.util.List;
// Importing required classes
import javax.validation.Valid;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

// Annotation
@RestController

// Class
public class DepartmentController {

    @Autowired private DepartmentService departmentService;

    // Save operation
    @PostMapping("/departments")
    public Department saveDepartment(
        @Valid @RequestBody Department department)
    {
        return departmentService.saveDepartment(department);
    }

    // Read operation
    @GetMapping("/departments")
    public List<Department> fetchDepartmentList()
    {
        return departmentService.fetchDepartmentList();
    }

    // Update operation
    @PutMapping("/departments/{id}")
    public Department
    updateDepartment(@RequestBody Department department,
                     @PathVariable("id") Long departmentId)
    {
        return departmentService.updateDepartment(
            department, departmentId);
    }

    // Delete operation
    @DeleteMapping("/departments/{id}")
    public String deleteDepartmentById(@PathVariable("id")
                                       Long departmentId)
    {
        departmentService.deleteDepartmentById(
            departmentId);
        return "Deleted Successfully";
    }
}

Accessing H2 Database

Below is the code for the application.properties file 

server.port = 8082

# H2 Database
spring.h2.console.enabled=true
spring.datasource.url=jdbc:h2:mem:dcbapp
spring.datasource.driverClassName=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=password
spring.jpa.database-platform=org.hibernate.dialect.H2Dialect

For application.yml file:

spring:
    h2:
        console.enabled=true
    datasource:
        url: jdbc:h2:mem:dcbapp
        driverClassName: org.h2.Driver
        username: sa
        password: password
    jpa:
        spring.jpa.database-platform: org.hibernate.dialect.H2Dialect

Now run your application and let’s test the endpoints in Postman and also refer to our H2 Database.

Testing the Endpoint in Postman

Endpoint 1: POST – http://localhost:8082/departments/ 

Endpoint 2: GET – http://localhost:8082/departments/ 

Endpoint 3: PUT – http://localhost:8082/departments/1

Endpoint 4: DELETE – http://localhost:8082/departments/1 

Lastly, H2 Database is as depicted in the below media as follows: 

Conclusion

In this article, we have learned how to configure, access H2 Database and how to test endpoints in Postman for managing the running database.