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

In this blog, will go through how to create REST APIs 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
  • Java 8
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

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