Following on from part 1, we will now make a Spring Boot rest service.
Create a project directory and we will work inside of their.
Inside your project directory, create this directory structure:
$ mkdir -p src/main/java/users
$ mkdir -p src/main/resources
We will be using maven to manage our dependencies, so create in the top level a pom.xml with the following content:
<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>org.springframework</groupId>
<artifactId>gs-postgresql-data</artifactId>
<version>0.1.0</version>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.0.0.RELEASE</version>
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<!-- JPA Data (We are going to use Repositories, Entities, Hibernate, etc...) -->
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>
<dependency>
<groupId>org.postgresql</groupId>
<artifactId>postgresql</artifactId>
<version>42.2.2</version>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<properties>
<java.version>1.8</java.version>
</properties>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
Then, we will create an application.properties inside our resources directory:
spring.datasource.url=jdbc:postgresql://localhost:5432/postgres spring.datasource.username=postgres spring.datasource.password=postgres spring.jpa.hibernate.ddl-auto=update
This allows us to update the database rather than create a new one every time with update instead of create.
Now, create the following classes inside the users directory:
Users.java
package users;
import javax.persistence.*;
import java.io.Serializable;
@Entity
@Table(name = "users")
public class Users implements Serializable {
private static final long serialVersionUID = -3009157732242241606L;
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private long id;
@Column(name = "username")
private String username;
protected Users() {
}
public String getUsername() {
return username;
}
public Users(String username) {
this.username = username;
}
@Override
public String toString() {
return String.format("Customer[id=%d, username='%s']", id, username);
}
}
UserRepository.java
package users;
import org.springframework.data.repository.CrudRepository;
/**
* This will be AUTO IMPLEMENTED by Spring into a Bean called userRepository
* CRUD refers Create, Read, Update, Delete
*/
public interface UserRepository extends CrudRepository<Users, Long> {
}
UserController.java
package users;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
@RestController
@RequestMapping(path="/users")
public class UserController {
@Autowired
private UserRepository userRepository;
@GetMapping(path="/add")
public @ResponseBody String addNewUser (@RequestParam String username) {
Users testuser = new Users(username);
userRepository.save(testuser);
return "done";
}
@GetMapping(path="/all")
public @ResponseBody Iterable getAllUsers() {
return userRepository.findAll();
}
}
Application.java
package users;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
Let’s test the application works.
Run:
$ mvn clean install spring-boot:run
Then, in a browser, run navigate to http://localhost:8080/users/add?username=johndoe then navigate to http://localhost:8080/users/all and this should display all the usernames stored in the database in json format.
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