Java Spring Boot REST Server with PostgreSQL

🕓 45 minutes

What you’ll learn

How to setup your application for :

  • connecting to the PostgreSQL database
  • getting data from REST API
  • providing data to REST API.

In this tutorial, we will create a simple java component with Java Spring Boot scaffolder with a connection to the PostgreSQL database storage. We want to expose a single REST endpoint for getting the basic client data information, creating a microservice CRUD layer above the DB storage.

clientDataDB

Project source

This example project can be cloned from: [email protected]:innobank/aia-spring-data-db.git

Prerequisites

  • Prepare your local development environment for CodeNOW with Spring Boot.
  • Run PostgreSQL locally.
    • You can run PostgreSQL directly or using docker compose.
    • The configuration file for docker-compose can be downloaded from the link that can be found in the section Docker compose and third-party tools of the Java Spring Boot Local Development tutorial.
  • Create a new component

Steps

Open your IDE, import the created component and start coding:

  • Add these maven dependencies to your pom.xml file:

    01 <dependency>
    02 <groupId>javax.persistence</groupId>
    03 <artifactId>javax.persistence-api</artifactId>
    04 <version>2.2</version>
    05 </dependency>
    01 <dependency>
    02 <groupId>org.springframework.boot</groupId>
    03 <artifactId>spring-boot-starter-data-jpa</artifactId>
    04 <version>2.3.3.RELEASE</version>
    05 </dependency>

  • Define the JPA entity Client. This simple table will store the basic client data:

    • Generate getters and setters with your IDE

      01 package org.example.service.repository.entity;
      02
      03 import java.time.LocalDate;
      04
      05 import javax.persistence.Entity;
      06 import javax.persistence.GeneratedValue;
      07 import javax.persistence.Id;
      08
      09 @Entity
      10 public class Client {
      11 @Id
      12 @GeneratedValue
      13 private Long id;
      14
      15 private String username;
      16 private String firstname;
      17 private String surname;
      18 private LocalDate birthdate;
      19 }

  • Create a new ClientRepository, which is a basic CRUD interface for Spring Boot data DB access:

  • Create a new controller and put all the parts together

    • For more details about Spring Boot controllers, see: https://docs.spring.io/spring/docs/3.0.0.M4/reference/html/ch15s03.html

      01 package org.example.service.controller;
      02
      03 import org.example.service.repository.ClientRepository;
      04 import org.example.service.repository.entity.Client;
      05 import org.springframework.beans.factory.annotation.Autowired;
      06 import org.springframework.web.bind.annotation.GetMapping;
      07 import org.springframework.web.bind.annotation.PathVariable;
      08 import org.springframework.web.bind.annotation.RequestMapping;
      09 import org.springframework.web.bind.annotation.RestController;
      10 import reactor.core.publisher.Flux;
      11
      12 import javax.validation.constraints.NotNull;
      13 import java.util.List;
      14
      15
      16 @RestController
      17 @RequestMapping("/db")
      18 public class ClientDataController {
      19
      20 private final ClientRepository clientRepository;
      21
      22 @Autowired
      23 public ClientDataController(ClientRepository clientRepository) {
      24 this.clientRepository = clientRepository;
      25 }
      26
      27 @GetMapping("/clients")
      28 public List<Client> listClients() {
      29 return clientRepository.findAll();
      30 }
      31
      32 @GetMapping("/clients/{username}")
      33 public Flux<Client> getClient(@PathVariable @NotNull String username) {
      34 return Flux.just(clientRepository.getClientByUsername(username));
      35 }
      36 }

  • Next prepare database configuration:

    • Go to the PgAdmin console (http://localhost:5050 if using compose-postgre from our Local development manual) and create a new db client-db with the scheme client-data.

    • Add maven dependency to your pom.xml:

      01 <dependency>
      02 <groupId>org.postgresql</groupId>
      03 <artifactId>postgresql</artifactId>
      04 <version>42.2.11</version>
      05 </dependency>

  • Now change the configuration in config/application.yaml:

    • Fill {db user} and {db password} according to your configuration

    • Make sure you follow yaml syntax (especially whitespaces)

      01 server:
      02 port: 8080
      03 spring:
      04 main:
      05 banner-mode: off
      06 zipkin:
      07 enabled: false
      08 datasource:
      09 url: jdbc:postgresql://localhost:5432/client-db?currentSchema=client-data
      10 username: {db user}
      11 password: {db password}
      12 driverClassName: org.postgresql.Driver
      13 jpa:
      14 properties:
      15 hibernate:
      16 dialect: org.hibernate.dialect.PostgreSQL95Dialect
      17 management:
      18 endpoints:
      19 web:
      20 exposure:
      21 include: health, prometheus

  • Try to build and run the application in your IDE. After startup, you should be able to access your new controller’s swagger: http://localhost:8080/swagger/index.html

clientDataDBSwagger1clientDataDBSwagger1

Deploy to CodeNOW

If your code works in the local development, you are ready to push your changes to GIT and try to build and deploy your new component version to the CodeNOW environment.

What’s next?

See our other developer guides: