Spring Boot with H2 Database

Shubhra SrivastavaSeptember 16th, 2019Last Updated: September 13th, 2019

0 457 2 minutes read

In this quick tutorial, we’ll bootstrap a simple Spring Boot application backed by an in-memory H2 database. We’ll use the Spring Data JPA to interact with our database.

Project Setup:

Firstly, let’s generate our project template using Spring Initializr:

On clicking the ‘Generate the project’ link, our project files will get downloaded.

Now, if we look closely at the generated POM file, we’ll have below added dependencies:

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

H2 Default Properties:

Since we have added H2 database dependency, Spring Boot will auto-configure its related properties. The default configurations include:

spring.datasource.url=jdbc:h2:mem:testdb
spring.datasource.driverClassName=org.h2.Driver
spring.datasource.username=sa
spring.datasource.password=
spring.h2.console.enabled=false

Let’s override a few of these properties by defining those in our application.properties file:

spring.h2.console.enabled=true
spring.h2.console.path=/h2
spring.datasource.url=jdbc:h2:mem:university

Here, our database name will be a university. We have also enabled the H2 Console and have set its context path.

Defining Entities:

Now, we’ll define a Student entity:

@Entity
public class Student {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Integer id;
  
    private String name;
     
    public Student(String name) {
        this.name = name;   
    }
  
    //getters, setters
  
    public String toString() {
        return "{id=" + id + ", name=" + name + "}";
    }
}

And its corresponding Spring Data JPA repository:

@Repository
public interface StudentRepository
  extends CrudRepository<Student, Integer> {
}

The Student entity will get mapped to the database table with exactly the same name. If we want, we can specify a different table name with @Table annotation.

The Application Class:

Finally, let’s implement our UniversityApplication class:

@SpringBootApplication
public class UniversityApplication {
  
    public static void main(String[] args) {
        SpringApplication.run(UniversityApplication.class, args);      
    }
  
    @Bean
    public CommandLineRunner testApp(StudentRepository repo) {
        return args -> {
            repo.save(new Student("James"));
            repo.save(new Student("Selena"));
  
            List<Student> allStudents = repo.findAll();
            System.out.println("All students in DB: " + allStudents);
  
            Student james = repo.findById(1);
            System.out.println("James: " + james);
        };
    }
}

This class is the starting point for our Spring Boot application. Here, the @SpringBootApplication annotation is equivalent to having @ComponentScan, @EnableAutoConfiguration, and @SpringConfiguration together.

We have also defined an instance of CommandLineRunner. And so, when we run our application, our console logs will have:

UniversityApplication:All students in DB: [{id=1, name=James}
 , {id=2, name=Selena}]
James: {id=1, name=James}
...

Please note that in Spring Boot, all entities should ideally be defined at either the same package level or at lower levels(in sub-packages) to that of the main application class. If so, Spring Boot will auto-scan all those entities.

Accessing the H2 Console:

We can also check the database entries on the H2 console.

To do that, we’ll open the URL: http://localhost:8080/h2 on any browser and use our database configurations to login. With it, we’ll be able to see all our created tables and entries easily on a UI Console dashboard.

Conclusion:

In this tutorial, we bootstrapped a very simple Spring Boot application with a single entity. This application is integrated with the H2 database and uses Spring Data JPA.
We can easily extend it to cater to a much wider application scope.

Published on Java Code Geeks with permission by Shubhra Srivastava, partner at our JCG program. See the original article here: Spring Boot with H2 Database

Opinions expressed by Java Code Geeks contributors are their own.

Do you want to know how to develop your skillset to become a Java Rockstar?

Subscribe to our newsletter to start Rocking right now!

To get you started we give you our best selling eBooks for FREE!

1. JPA Mini Book

2. JVM Troubleshooting Guide

3. JUnit Tutorial for Unit Testing

4. Java Annotations Tutorial

5. Java Interview Questions

6. Spring Interview Questions

7. Android UI Design

and many more ....