Start web application development with Spring Boot

Overview

--Try to make a simple web application with Spring Boot ――In this article, first of all, something like Hello World -** Even people with no development experience can easily get started **

What is Spring Boot in the first place?

--One of the frameworks in Java development --The feature is that it requires less initial settings and is easy to start using.

Development environment

--Java must be installed in the development environment

• https://eng-entrance.com/java-install-jdk-mac --Windows people can also install by the above method if they read it as appropriate. --Any IDE is OK (Eclipse, etc.)

Creating a template

Use Spring Initializr

--Web service that allows you to create a template application for Spring Boot --You can select the build tool (Maven / Gradle) and language (Java / Kotlin / Groovy).

• https://start.spring.io/

procedure

Specify the following

--Build tool ――Both are commonly used, so either one is fine, but this time I will use Gradle. --Language --Spring Boot version

• Project name
• anything is fine. This time it will be spring-study --Library used --Add Spring Web (easy to build MVC application) --Can be added later

--Click the Generate button to download the template app as a zip

Check the template app

--Files such as SpringStudyApplication.java and ʻapplication.properties are created by default --SpringStudyApplicationTests.java` is unnecessary, so delete it

Try Hello World

――If you keep the template, it won't work, so first of all, Hello World --When accessing http: // localhost: 8080 / hello, Hello World! Is displayed.

procedure

--Create a class that accepts requests and returns strings

HelloRestController.java

--Create HelloRestController.java in com.examle.springstudy

com.examle.springstudy.HelloRestController.java

package com.example.springstudy;

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

@RestController // ①
public class HelloRestController {
    @GetMapping("/hello") // ②
    public String hello() {
        return "Hello World!";
    }
}

--Two annotations are the point (@ XXX) -①: Indicates that the controller accepts requests and returns responses. -②: Associate the request URL with the logic

Operation check

--Select the starting class (SpringStudyApplication) and execute (⌃ + ⌥ + R)

--When started, the following contents are output to the console.

11:46:44: Executing task 'bootRun'...

> Task :compileJava
> Task :processResources
> Task :classes

> Task :bootRun

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.2.1.RELEASE)

2019-12-01 11:46:59.590  INFO 43520 --- [           main] c.e.springstudy.SpringStudyApplication   : Starting SpringStudyApplication on MacBookPro with PID 43520 (/Users/tanibuchi/Desktop/spring-study/spring-study/build/classes/java/main started by tanibuchi.kosuke in /Users/tanibuchi/Desktop/spring-study/spring-study)
2019-12-01 11:46:59.595  INFO 43520 --- [           main] c.e.springstudy.SpringStudyApplication   : No active profile set, falling back to default profiles: default
2019-12-01 11:47:00.598  INFO 43520 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2019-12-01 11:47:00.612  INFO 43520 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2019-12-01 11:47:00.612  INFO 43520 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.27]
2019-12-01 11:47:00.680  INFO 43520 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2019-12-01 11:47:00.680  INFO 43520 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 1037 ms
2019-12-01 11:47:00.915  INFO 43520 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2019-12-01 11:47:01.089  INFO 43520 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2019-12-01 11:47:01.098  INFO 43520 --- [           main] c.e.springstudy.SpringStudyApplication   : Started SpringStudyApplication in 2.169 seconds (JVM running for 3.005)

--If Started is displayed at the end, it can be started normally. --When you access http: // localhost: 8080 / hello, the following screen will be displayed.

Finally

――You can easily start application development using Spring Boot like this. ――This time, it is described at the summary level, so I will explain it a little more carefully next time.