Developing a microservice from zero with Java and Spring Boot

This repository contains all the files related with the conference.

Context

You are hired as a developer for one company that sell product for different part of the world. Actually the company have the information about countries, cities, and airports distribute on multiples APIS with tons of duplicate code.

Your manager suggested that you create a new API that contain all the logic to create, update, and obtain the information about all the entities related with countries in a way that anyone can use it.

Requirements

To create your microservice you need to have in your machine the following things:

• Java
• Maven
• Git
• Docker

If you don't have some of these tools in your machine installed, please follow the instructions in the official documentation of each tool.

Check requirements

If you have installed on your machine some of these tools previously or you installed all the tools now, please check if everything works fine.

• Check which version of Java you have using the following command:

  % java -version
  openjdk version "11.0.8" 2020-07-14
  OpenJDK Runtime Environment (build 11.0.8+10)
  OpenJDK 64-Bit Server VM (build 11.0.8+10, mixed mode, sharing)
  

• Check whether your Maven version is 3.0.0 or up. You can see which version of Maven you have using the following command:

  % mvn --version
  Apache Maven 3.0.0
  Maven home: /usr/share/maven
  

• Check whether the version of Docker in your machine is 18.09.0 or higher. You can check the version of Docker using the following command:

  % docker --version
  Docker version 18.09.0, build 369ce74a3c
  

Milestones

This talk has different milestones with the idea that you can start on any part.

1. Create the basic skeleton using Spring Initializr
2. Create a basic CRUD (controller and service) that mocks the response
3. Add the validators to prevent possible problems
4. Add handlers to capture all the errors
5. Add the logic to persist the information using Spring Data
6. Add the helper's endpoints (info and health)
7. Add the documentation using Open API 3
8. Add some unit tests using Junit5
9. Add different configuration
10. Package the source code on Docker

Extra points

These milestones could not appear in the talk depending on the available time.

11. Add logs on the application
12. Prevent conflicts using Enforcer

FAQ

Which version of the JDK can I use on this project?

There is no restriction about which version, in particular, you need to consider that exist different alternatives to the JDK:

• OracleJDK: This version was free until Java 11, after this version you can use it for development/test environments, but you need to pay a license to use it on production. This version of the JDK offers to you the most recent patches of bugs and new features because Oracle is the owner of the language.

• OpenJDK: When Oracle bought Sun Microsystems created this as an open-source alternative that all the developers can use in any environment without restrictions. The main problem with this version is the patches of the bugs take time to appear in a case that is not critical.

Take into consideration that there are other alternatives but according to Snyk 2021 Report, most of the developers use OpenJDK.

Which tools can I use for development?

Many free tools support Kotlin development. Here are two you may like:

• IntelliJ IDEA Community Edition – IntelliJ is the most widely used IDE for Kotlin development. IntelliJ IDEA Community Edition provides everything you need to start Kotlin and Spring.

• Eclipse – Eclipse is another IDE option for Kotlin development. Most plugins are free and have a vast community of developers who frequently update them. Take into consideration that to use Kotlin on this IDE, you need to install a plugin, you can follow the instructions on the official webpage of Kotlin.

Take into consideration that there are other IDE but according to Snyk 2021 Report, most of the JVM developers use Eclipse and Intellij, but the use of Visual Studio code is growing in the last year.

Further readings

Here are some links where you can have more information about Spring. Please take into consideration that some of them you need to pay it.

• Spring Tutorials - Baeldung
• Spring Start Here - Laurențiu Spilcă
• Spring Microservices in Action, Second Edition - John Carnell, Illary Huaylupo Sánchez
• Spring Developer - Youtube channel