Spring Boot H2

In this technical post we will review how to integrate an H2 in memory database in a Spring Webflux application. Please read this previous Spring Webflux Basics before conitnue with this information. Then, let’s create a new Spring Boot project with Webflux, Lombok, JPA and H2 as dependencies:

spring init --dependencies=webflux,lombok,jpa,h2 --language=java --build=gradle spring-boot-h2

Here is the complete build.gradle file generated:

plugins {
  id 'org.springframework.boot' version '2.1.4.RELEASE'
  id 'java'
}

apply plugin: 'io.spring.dependency-management'

group = 'com.jos.dem.springboot.h2'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '11'

repositories {
  mavenCentral()
}

dependencies {
  implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
  implementation 'org.springframework.boot:spring-boot-starter-webflux'
  runtimeOnly 'com.h2database:h2'
  compileOnly('org.projectlombok:lombok')
  annotationProcessor('org.projectlombok:lombok')
  testImplementation 'org.springframework.boot:spring-boot-starter-test'
  testImplementation 'io.projectreactor:reactor-test'
}

Let’s start by creating a person model so that we can store this entity in our H2 database

package com.jos.dem.springboot.h2.model;

import javax.persistence.Id;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;

import lombok.NoArgsConstructor;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.Getter;
import lombok.Setter;

@Entity
@NoArgsConstructor
@AllArgsConstructor
@Data
public class Person {

	@Id
	@GeneratedValue
	private Long id;
	private String nickname;
	private String email;

}

And here is our PersonRepository, by extending JpaRepository we get a bunch of generic CRUD methods into our type that allows save, find all persons and so on, also will allow Spring Data JPA repository infrastructure to scan the classpath for this interface and create a Spring bean for it.

package com.jos.dem.springboot.h2.repository;

import java.util.List;

import org.springframework.data.jpa.repository.JpaRepository;
import com.jos.dem.springboot.h2.model.Person;

public interface PersonRepository extends JpaRepository<Person, Long>{

  Person save(Person person);
  List<Person> findAll();

}

Next, we are going to use CommandLineRunner to populate our person table. The CommandLineRunner is a call back interface in Spring Boot, when Spring Boot starts will call it and pass in args through a run() internal method.

package com.jos.dem.springboot.h2;

import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.autoconfigure.domain.EntityScan;
import org.springframework.context.annotation.Bean;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;

import com.jos.dem.springboot.h2.model.Person;
import com.jos.dem.springboot.h2.repository.PersonRepository;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@SpringBootApplication
@EntityScan("com.jos.dem.springboot.h2.model")
@EnableJpaRepositories("com.jos.dem.springboot.h2.repository")
public class H2Application {

  private Logger log = LoggerFactory.getLogger(this.getClass());

  public static void main(String[] args) {
    SpringApplication.run(H2Application.class, args);
  }

  @Bean
  CommandLineRunner start(PersonRepository personRepository){
    return args -> {
      Person person  = new Person(1L, "josdem", "joseluis.delacruz@gmail.com");
      personRepository.save(person);
      personRepository.findAll().forEach(p -> log.info("person: {}", p));
    };
  }

}

H2 provides a web interface called H2 Console. Let’s enable that console in our application.properties.

spring.h2.console.enabled=true
spring.h2.console.path=/h2-console
spring.datasource.url=jdbc:h2:mem:persondb
spring.datasource.username=sa
spring.datasource.password=
spring.datasource.driver-class-name=org.h2.Driver
spring.datasource.platform=h2

The final step is to add spring-boot-starter-web dependency in order to get this H2 console work.

implementation 'org.springframework.boot:spring-boot-starter-web'

Now, if you start our application, you should see this output

2019-05-02 09:14:42.378  INFO 8960 --- [main] com.jos.dem.springboot.h2.H2Application  : Started H2Application in 4.944 seconds (JVM running for 5.357)
2019-05-02 09:14:42.492  INFO 8960 --- [main] o.h.h.i.QueryTranslatorFactoryInitiator  : HHH000397: Using ASTQueryTranslatorFactory
2019-05-02 09:14:42.609  INFO 8960 --- [main] ication$$EnhancerBySpringCGLIB$$de299e81 : person: Person(id=1, nickname=josdem, email=joseluis.delacruz@gmail.com)

And the H2 console in this URL: http://localhost:8080/h2-console

To run the project:

gradle bootRun

To browse the project go here, to download the project:

git clone git@github.com:josdem/spring-boot-h2.git

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