Spring Boot with H2

In this tutorial, we will examine the usage of the in-memory database h2 in a Spring Boot application.
H2 is an in-memory database, we can use it for simple case-studies and quick show cases.

Maven Dependencies

This can be easily generated with Spring Starter.
The dependency for Spring Data and JPA:

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

The dependency for H2:

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

H2 Configuration

Now, we can configure the database settings in application.properties file:

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

The last line is for accessing H2 GUI console to query the database via SQL statements.
When the applications starts, we can access the GUI by navigating to:
http://localhost:8080/h2-console

Initial Data

To create initial tables and insert sample data into the tables, Spring Boot reads the file data.sql and runs ddl and dml in the file.

CREATE TABLE books (
  id INT PRIMARY KEY,
  name VARCHAR(120) NOT NULL,
  author VARCHAR(120) NOT NULL
);

INSERT INTO books (id, name, author) 
VALUES
  (1, 'Java Persistence', 'John Mohn'),
  (2, 'H2 Database', 'Lhan Mhan');

For more information about H2 database you can refer to:
http://www.h2database.com