Introduction to Java development environment & Spring Boot application created with VS Code

Hello everyone. I will write an article for ** Java Advent Calendar 2020 (Qiita) Day 24 **.

Introduction

I have been developing in Java for a long time, but most of the editors I use for projects are eclipse (or STS) or IntelliJ IDEA. Once you get used to InteliJ, you can choose ** InteliJ ** even if you pay the license! It was, but I suddenly touched ** Visual Studio Code ** and it feels good! It was. In this article, I would like to build a Java development environment ** with Visual Studio Code.

Also, this time, I would like to create a simple application created with "** Spring MVC, Spring Boot **" (framework), which is often used in Java development.

Assumed development environment

OS: Windows10 ** Visual Studio Code **: 1.51.1 (December 2020)

• Assuming that VS Code and JDK have already been installed I wrote an article about installing the JDK before, so please refer to it! Amazon Corretto 11 Installation

Procedure (3 steps)

1. Java Extension Pack installation
2. Let's run Java!
3. Let's create a Spring Boot application!

Step 1: Install Java Extension Pack

--Launch Visual Studio Code and install the extension: Java Extension Pack.

• Java Extension Pack
  https://marketplace.visualstudio.com/items?itemName=vscjava.vscode-java-pack

Install other extensions that you might use often.

• Maven for Java
  https://marketplace.visualstudio.com/items?itemName=vscjava.vscode-maven
• Spring Boot Extension Pack
  https://marketplace.visualstudio.com/items?itemName=Pivotal.vscode-boot-dev-pack

Step 2: Let's run Java!

--Display the "Command Palette" (Ctrl + Shift + p) in Visual Studio Code and execute the [** Java: Create Java Project **] command to create a Java project.

>Java: Create Java Project

No build tools

• Enter the name of the Java project to be created → Project creation completed

--File and directory structure of the created Java project

helloworld
├── lib
└── src
    └── App.java

Compile "App.java" created by default and execute the generated class file → "Hello, World!" Is displayed.

$ javac App.java
$ java App
Hello, World!

Step 3: Let's create a Spring Boot application!

Since you installed the "Spring Boot Extension Pack" in step 2, let's create a Spring Boot application.

Creating a project

--Display "** Command Palette **" (Ctrl + Shift + p) in Visual Studio Code and create a Spring boot project.

Operation on the command palette

1. Select "Spring Initializr: Generate a Maven Project"
2. "Specify Spring Boot version" Select the version of Spring Boot. Since there is no particular designation this time, select the latest (2.4.0) as of 2020/12
3. "Specify project language" Select the language to use. Select Java this time
4. Enter the "Input Group Id" package name.

Example: com.example

 5. Enter the "Input Artifact Id" project name.
```Example: demo```
 6. "Specify packaging type" Package type: War this time. (Jar is OK)
 7. "Specify Java type" You will be asked for the Java version to use, so select the Java version to use. Java 14 is used this time.
 8. "Search for dependencies" Since it is a Maven project, you have to select dependencies. This time, the purpose is to "create a web application" and "display the screen", so select the following two.
```spring web / thymeleaf

At this point, you will be asked where to save the project. Select a location to save the project.

--The created directory has the following structure. -** DemoApplication.java **, ** ServletInitializer.java ** are implemented by default.

|― src
 |   |― main
 |   |    |― java
 |   |    |    |― com
 |   |    |        |― example
 |   |    |             |― demo(Project name)
 |   |    |                      |― DemoApplication.java (created by default)
 |   |    |                      |― ServletInitializer.java (created by default)
 |   |    |― resources
 |   |           |― static/ (Static file)
 |   |           |― templates/ (Template file)
 |   |           |― application.properties (Environment-specific configuration file)
 |   |― test
 |       |― java
 |            |― com
 |                |― example
 |                      |― demo(Project name)
 |                               |― DemoApplicationTests.java
 |― .gitignore
 |― HELP.md
 |― mvnw
 |― mvnw.cmd
 |― pom.xml (Maven config file)

Creating an application

-Create a Controller class under the \ demo \ src \ main \ java \ com \ example \ demo \ controller directory. (SampleController.java)

 package com.example.demo.controller;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class SampleController {
    @RequestMapping("/sample")
    public String sample() {
        return "sample";
    }
}

Create sample.html in \ demo \ src \ main \ templates. (Sample.html)

<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <title>Sample</title>
</head>

<body>
    <h1>Hello World!</h1>
</body>

</html>

--Run Spring boot application Select "** SPRING-BOOT DASHBOARD **" at the bottom left of VS Code and select [start] or [debug]

• Tomcat included in Spring Boot starts and the implemented application is compiled.

Display confirmation

--Check the display on your browser. You should see "Hello World!". http://localhost:8080/sample

At the end

It had a lot of extensions and was easier to use than I had imagined! I'm worried about continuing to use VS Code without renewing my InteliJ license ... In the future, I will strive to publish more practical Java articles.

The last day is @tkxlab!

reference

I tried to display "Hello World" with VS Code for Spring Boot https://tech-lab.sios.jp/archives/19941