Spring Boot Restful Service with JPA Configuration and H2 in-memory database

Hello everyone, Today we will learn how to create REST API using Spring Boot, JPA and H2 In-memory database 

Following technologies stack being used:

• Spring Boot 2.1.1.RELEASE
• Spring 5.1.3.RELEASE 
• Maven 3
• JDK 1.8
• Eclipse Oxygen
• Free Maker
• Hibernate 5.3.7
• HikariCP 3.2.0
• H2 in-memory database 1.4.197

1)Project Structure

2)Maven/Dependency Management [pom.xml] 

<?xml version="1.0" encoding="UTF-8"?>

<project xmlns="http://maven.apache.org/POM/4.0.0"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 

https://maven.apache.org/xsd/maven-4.0.0.xsd">

<modelVersion>4.0.0</modelVersion>

<parent>

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-starter-parent</artifactId>

<version>2.1.1.RELEASE</version>

<!-- lookup parent from repository -->

</parent>

<groupId>com.knowledgefactory</groupId>

<artifactId>springboot-CRUD-HSQLDB</artifactId>

<packaging>jar</packaging>

<version>0.0.1-SNAPSHOT</version>

<name>springboot-CRUD-HSQLDB</name>

<description>Demo project for springboot-CRUD-HSQLDB</description>

<properties>

<java.version>1.8</java.version>

</properties>

<dependencies>

<dependency>

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-starter</artifactId>

</dependency>

<!-- spring mvc, rest -->

<dependency>

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-starter-web</artifactId>

</dependency>

<dependency>

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-starter-data-jpa</artifactId>

</dependency>

<dependency>

<groupId>com.h2database</groupId>

<artifactId>h2</artifactId>

</dependency>

</dependencies>

<build>

<plugins>

<plugin>

<groupId>org.springframework.boot</groupId>

<artifactId>spring-boot-maven-plugin</artifactId>

</plugin>

</plugins>

</build>

</project>

3)Controller

package com.knowledgefactory.knowledgefactorydemo;

import java.util.ArrayList;

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.http.HttpStatus;

import org.springframework.http.ResponseEntity;

import org.springframework.web.bind.annotation.GetMapping;

import org.springframework.web.bind.annotation.RestController;

import com.knowledgefactory.Entity.User;

import com.knowledgefactory.Repository.UserRepository;

import com.knowledgefactory.VO.UserVo;

@RestController

public class HomeController {

@Autowired

UserRepository repository;

@GetMapping({ "/", "/getcall" })

public ResponseEntity<List<UserVo>> listAllUsers() {

List<User> userList = new ArrayList<>();

userList = (List<User>) repository.findAll();

List<UserVo> vo = new ArrayList<>();

for (User users : userList) {

UserVo obj = new UserVo();

obj.setId(users.getId());

obj.setName(users.getName());

vo.add(obj);

}

return new ResponseEntity<List<UserVo>>(vo, HttpStatus.OK);

}

}

4)Entity Class

package com.knowledgefactory.Entity;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.GenerationType;

import javax.persistence.Id;

@Entity

public class User {

@Id

@GeneratedValue(strategy = GenerationType.AUTO)

private Long id;

private String name;

public User() {

}

public User(String name) {

this.name = name;

}

public Long getId() {

return id;

}

public void setId(Long id) {

this.id = id;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public User(Long id, String name) {

super();

this.id = id;

this.name = name;

}

}

5)VO Class

package com.knowledgefactory.VO;

public class UserVo {

private String name;

private Long id;

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public Long getId() {

return id;

}

public void setId(Long id) {

this.id = id;

}

}

6)Repository

package com.knowledgefactory.Repository;

import java.util.List;

import org.springframework.data.repository.CrudRepository;

import org.springframework.stereotype.Repository;

import com.knowledgefactory.Entity.User;

@Repository

public interface UserRepository extends CrudRepository<User, Long> {

List<User> findByName(String name);

}

7)Spring Boot

package com.knowledgefactory.knowledgefactorydemo;

import org.slf4j.Logger;

import org.slf4j.LoggerFactory;

import org.springframework.beans.factory.annotation.Autowired;

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.ComponentScan;

import org.springframework.data.jpa.repository.config.EnableJpaRepositories;

import com.knowledgefactory.Entity.User;

import com.knowledgefactory.Repository.UserRepository;

@EnableJpaRepositories(basePackages = "com.knowledgefactory.Repository")

@SpringBootApplication

@ComponentScan({ "com" })

@EntityScan("com.knowledgefactory.Entity")

public class KnowledgefactorydemoApplication implements CommandLineRunner {

private static final Logger log = LoggerFactory.

getLogger(KnowledgefactorydemoApplication.class);

@Autowired

private UserRepository repository;

public static void main(String[] args) {

SpringApplication.run(KnowledgefactorydemoApplication.class, args);

}

@Override

public void run(String... args) throws Exception {

log.info("StartApplication...");

repository.save(new User("Knf"));

repository.save(new User("sibin"));

}

}

8)application.properties

logging.level.org.springframework=INFO

logging.level.com.knowledgefatory*=INFO

logging.level.com.zaxxer=DEBUG

logging.level.root=ERROR

server.port=8081

9)Run

$ mvn spring-boot:run

10)Test

Download Source Code

$ git clone  https://github.com/knowledgefactory4u/KnowledgeFactory