Integrate H2 database with SpringBoot & Spring JPA in Embedded mode

H2 database is a pure Java, open source and very fast engine. We can use H2 for development, testing and performance benchmarking. So in the tutorial, JavaSampleApproach will show how to integrate H2 database with SpringBoot and Spring JPA in Embedded mode.

I. H2 database and SpringBoot integration

H2 database has small footprint (smaller than 1.5 MB) with low memory requirements. It supports for multiple schemas and standard SQL, JDBC API. We can use H2 with disk based or in-memory databases.

H2 can be built by following mode:
– Embedded mode (local connections)
– Server mode (remote connections)
– Mixed mode (local and remote connections)

In the tutorial, We focus on Embedded mode to integrate H2 database and SpringBoot Application.

H2 Embedded

With Embedded Mode, an application uses JDBC to create a H2 database within the same JVM so it’s very fast to exchange data.

How to configure it with SpringBoot?
-> Spring Boot has a built in H2 database, so We just add below dependency:

H2 supports a convenient web based data console to interact with database while the development:

H2 Database - console

II. Practice

In the tutorial, We create a Spring JPA Web application which uses Spring JPA to interact with H2 database in Embedded mode.

Step to do:
– Create SpringBoot project
– Configure H2 database
– Implement Spring JPA Web Application
– Run & check results

1. Create SpringBoot project

– Using SpringToolSuite, create a SpringBoot project. Then add list dependencies {web, jpa, h2}:

2. Configure H2 database

Open file, add configurations:

Set spring.h2.console.enabled is true to enable web console of H2 database.
spring.h2.console.path is used to define H2 console’s url.
Default setting values of H2 database:
username/password: sa/’blank’
driverClassName: org.h2.Driver
datasource.url: jdbc:h2:mem:testdb

jdbc:h2:mem is used to define In-memory databases.
jdbc:h2:file is used to define disk-based databases.

3. Implement Spring JPA Web Application
3.1 Create Customer model

Annotation @Entity indicates that Customer is an Entity and @Table specifies the primary table (name customer) for the annotated @Entity.

@ID specifies the primary key and @GeneratedValue indicates generation strategy for value of primary key.

@Column: mapped column (in the table) for persistent fields (in Java class).

3.2 Create CustomerRepository

This interface helps us do all CRUD functions for class Customer.

3.3 Create a WebController

Create 3 @RequestMapping:
– @RequestMapping(“/save”)
– @RequestMapping(“/findall”)
– @RequestMapping(“/findbyid”)

In the web controller methods which are annotated by @RequestMapping, we have used some methods of autowired repository which are implemented interface CrudRepository:

and the method findByLastName that we create in our interface CustomerRepository.

4. Run & check results

Build and Run the SpringBoot with commandlines: mvn clean install and mvn spring-boot:run.
Make a request: http://localhost:8080/h2_console

H2 database - make console request

Input login’s info as above image. Then press Connect, and makes a first select for customer table:

H2 database - first view

Make a request: http://localhost:8080/save

Now again select customer table:

h2 database - select customers

Make a request: http://localhost:8080/findall,

h2 database - findall

Make a request http://localhost:8080/findbyid?id=5,

h2 database - find by id

Now, do restart the SpringBoot App, then select customer table again:

h2 database - customer after restart

-> Because we use Disk-memory database by setting: spring.datasource.url=jdbc:h2:file:~/h2/testdb.

III. Sourcecode


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