[JAVA] Learning Spring Boot [Beginning]

I've been touching Java for a while at work, but I haven't had a chance to touch the trendy frameworks, but when I look at Spring Boot somehow, maybe this time it will take root as a standard framework. What? There is no loss to remember. I decided to touch it.

[Starter Project]

This is my first Spring Boot project creation, but since there is no other choice, it may be a standard, but I will start from here.

    1. Project setting 1 Gradle is easy for me to see the settings, so I will use it. The package is war because I don't know the jar yet.


  1. Project setting 2 For the time being, I just want to move it, so I chose only the template engine and the web Maybe I can add it later. start_2.png

    1. Contents of automatic generation It was automatically generated as shown below. start_3.png
  2. Creating a controller Controller is mainly used as a controller for Web pages. RestController is used in the controller for WebAPI that returns Json, XML, etc. However, I would like to try both. First, create it from RestController.


package com.example.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

public class TestRest {

	public String Rest() {
		return "This is Rest";



  1. Try to run Select "Spring Boot Application" in Run start_5.png

  2. Try to access from a browser It seems that Tomcat is working, but can't find the controller I created? What on earth do you mean? start_6.png

  3. Try moving the RestController to the package where the Spring Boot Application is located start_7.png

  4. Access from the browser again For some reason, it worked! Does that mean that you can only create a controller under the Spring Application? start_8.png

  5. I will try to create a package under Spring Application.


package com.example.demo.controller;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

public class TestRest {

	public String Rest() {
		return "This is Rest. From the package under demo";


After all, that's right. start_9.png Anyway, my understanding has improved a little. RestController should be about this. Proceed to the next. Let's use the template engine with Controller.

10. Let's make a Controller.

Create index.html in the "templates" folder.


<!DOCTYPE html>
<meta charset="UTF-8">
<title>First Thymeleaf</title>
 <h1 th:text="${message}"></h1>

Create "TestController.java" in com.example.demo.controller.


package com.example.demo.controller;

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

public class TestController {

	public String index(Model model) {
		model.addAttribute("message", "Thymeleaf has moved!");
		return "index";



  1. Execute and check the operation of templates It worked! I'm happy. You can come to this point smoothly without being conscious of anything about the character code and without garbled characters. Spring Boot looks pretty good. Next, let's make a form. start_11.png

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