h2 JPA #2

https://github.com/spring-boot-tutorials/spring-data-h2-jpa-2

In this article we will configure Spring Boot to connect to an h2 database via JPA.

Create Initial Code Base

Go to https://start.spring.io/
Add the following dependencies: - jpa - h2 - JDBC
Click Generate

Dependencies

Dependencies used in pom.xml

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
    <groupId>com.h2database</groupId>
    <artifactId>h2</artifactId>
</dependency>
<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.18.38</version>
</dependency>

Properties

In src/main/resources/application.properties let’s add the following properties so the Spring Boot application can connect to the database

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

#spring.jpa.database=POSTGRESQL
spring.jpa.show-sql=true
spring.jpa.hibernate.ddl-auto=none
#spring.jpa.database-platform=org.hibernate.dialect.H2Dialect

# enables H2 console http://localhost:8080/h2-console
spring.h2.console.enabled=true
#spring.h2.console.path=/h2-console

data.sql

Create a new file src/main/resources/data.sql:

-- Spring Boot will automatically pick up the data.sql and run
-- it against our configured H2 database during application startup.
-- This is a good way to seed the database for testing or other purposes

DROP TABLE IF EXISTS billionaire;
CREATE TABLE billionaire (
  id INT AUTO_INCREMENT PRIMARY KEY,
  first_name VARCHAR(250) NOT NULL,
  last_name VARCHAR(250) NOT NULL,
  career VARCHAR(250) DEFAULT NULL
);

INSERT INTO billionaire (first_name, last_name, career) VALUES
  ('Aliko', 'Dangote', 'Billionaire Industrialist'),
  ('Bill', 'Gates', 'Billionaire Tech Entrepreneur'),
  ('Folrunsho', 'Alakija', 'Billionaire Oil Magnate');

Model

Let’s create a new POJO src/main/java/com/example/Billionaire.java

@Entity
@Data
@SuperBuilder
@NoArgsConstructor
public class Billionaire {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @NonNull
    private String firstName;

    @NonNull
    private String lastName;

    @NonNull
    private String career;
}

Repository

Next we will create a Spring repository to CRUD against the database

@Repository
public interface BillionaireRepository extends CrudRepository<Billionaire, Long> {

    // Automatic Custom Query
    List<Billionaire> findByFirstName(String name);

    // Manual Custom Query #1
    @Query(value = "SELECT * FROM BILLIONAIRE u WHERE u.first_name = ?1", nativeQuery = true)
    List<Billionaire> retrieveByName1(String firstName);

    // Manual Custom Query #2
    @Query(value = "SELECT * FROM BILLIONAIRE u WHERE u.first_name = :name", nativeQuery = true)
    List<Billionaire> retrieveByName2(@Param("name") String firstName);
}

Main

Now let’s use this repository.

Go back to MainApplication.java and add the following:

@SpringBootApplication
public class JpaH2ExampleApplication implements CommandLineRunner {

    public static void main(String[] args) {
            SpringApplication.run(JpaH2ExampleApplication.class, args);
    }

    @Autowired
    BillionaireRepository billionaireRepository;


    @Override
    public void run(String... args) throws Exception {
            // 1. INSERT
            Billionaire saved = billionaireRepository.save(Billionaire.builder()
                            .firstName("marcus")
                            .lastName("chiu")
                            .career("software engineer")
                            .build());
            System.out.println("1. " + saved);

            // 2. AUTO CUSTOM QUERY
            List<Billionaire> p = billionaireRepository.findByFirstName("marcus");
            System.out.println("2. " + p);

            // 3. MANUAL CUSTOM QUERY #1
            p = billionaireRepository.retrieveByName1("marcus");
            System.out.println("3. " + p);

            // 3. MANUAL CUSTOM QUERY #2
            p = billionaireRepository.retrieveByName2("marcus");
            System.out.println("4. " + p);
    }
}

Run Application

Open terminal at project root and execute the following:

mvn spring-boot:run

There should be no errors and the output will display all the CRUD operations.