IntelliJ IDEA 2020.2 Help

Tutorial: Create your first Spring application

This tutorial describes how to create and run a Spring application in IntelliJ IDEA. It will be a Spring Boot Maven project generated by Spring Initializr. This is the quickest way to create a Spring application, and IntelliJ IDEA provides a dedicated project wizard for it. You will learn how to expose an HTTP endpoint and map it to a method that returns a greeting to the user when accessed through a web browser.

Create a new Spring Boot project

  1. From the main menu, select File | New | Project.

  2. In the left pane of the New Project wizard, select Spring Initializr.

  3. From the Project SDK list, select the JDK that you want to use in your project.

    If the JDK is installed on your computer, but not defined in the IDE, select Add JDK and specify the path to the JDK home directory.

    If you don't have the necessary JDK on your computer, select Download JDK.

    For this tutorial, select the latest available JDK (version 14 or later).

  4. Select the default https://start.spring.io/ service and click Next.

    Spring Initializr in the New Project wizard
  5. Leave the default project settings and click Next.

    Spring Initializr Project Settings
  6. Select the Spring Web dependency under Web and click Next.

    This dependency is required for any web application that uses Spring MVC.

    Spring Dependencies in the New Project wizard
  7. Leave the default project configuration and click Finish.

    New project name

Add a method that sends a greeting

Spring Initializr creates a class with the main() method to bootstrap your Spring application. In this tutorial, we'll add the sayHello() method directly to this class.

  1. Open the DemoApplication.java file under src/main/java/com/example/demo.

    IntelliJ IDEA provides the Go to File action to quickly find and open files. From the main menu, select Navigate | File or press Ctrl+Shift+N, start typing the name of the file and select it from the list.

  2. Add the sayHello() method and the necessary annotations so that the file looks like this:

    package com.example.demo; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RequestParam; import org.springframework.web.bind.annotation.RestController; @SpringBootApplication @RestController public class DemoApplication { public static void main(String[] args) { SpringApplication.run(DemoApplication.class, args); } @GetMapping("/hello") public String sayHello(@RequestParam(value = "myName", defaultValue = "World") String name) { return String.format("Hello %s!", name); } }

    The sayHello() method takes the name parameter and returns the word Hello combined with the parameter value. Everything else is handled by adding Spring annotations:

    • The @RestController annotation marks the DemoApplication class as a request handler (a REST controller).

    • The @GetMapping("/hello") annotation maps the sayHello() method to GET requests for /hello.

    • The @RequestParam annotation maps the name method parameter to the myName web request parameter. If you don't provide the myName parameter in your web request, it will default to World.

Run your Spring application

IntelliJ IDEA creates a Spring Boot run configuration that you can use to run your new Spring application.

  • Press Alt+Shift+F10 and select the DemoApplication configuration.

    Alternatively, if you have the DemoApplication configuration selected in the main toolbar at the top, you can press Shift+F10 to run it.

    Or you can open the DemoApplication.java file and press Ctrl+Shift+F10. There are also gutter icons next to the class and main() method declarations that you can click to run your application: The Run gutter icon.

By default, IntelliJ IDEA shows your running Spring Boot application in the Services tool window. If it does not open automatically, select View | Tool Windows | Services from the main menu or press Alt+8.

The Services tool window with a running Spring Boot application

The Console tab shows the output of Spring log messages. By default, the built-in Apache Tomcat server is listening on port 8080. Open your web browser and go to http://localhost:8080/hello. If you did everything right, you should see how your application responds with Hello World!.

Spring Boot Hello World response in the browser

This is the default generic response. You can provide a parameter in your web request to let the application know how to greet you properly. For example, try http://localhost:8080/hello?myName=Human.

Add a home page

The created Spring Boot application has one endpoint available at /hello. However, if you open the root context of your application at http://localhost:8080/, you will get an error because there is no root resource defined. Let's add a static HTML home page with links to your endpoint

  1. Create the index.html file under /src/main/resources/static/.

    In the Project tool window, select the /src/main/resources/static/ directory, and then select File | New | HTML File from the main menu or press Alt+Insert and select HTML File.

  2. Modify the default template or replace it with the following HTML code:

    <!DOCTYPE HTML> <html> <head> <title>You first Spring application</title> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> </head> <body> <p><a href="/hello">Greet the world!</a></p> <form action="/hello" method="GET" id="nameForm"> <div> <label for="nameField">How should the app call you?</label> <input name="myName" id="nameField"> <button>Greet me!</button> </div> </form> </body> </html>
  3. Restart your Spring application as described in the previous procedure.

Now your application will serve index.html as the root resource at http://localhost:8080/.

What next?

This simple application demonstrates how to get started with Spring. To learn how IntelliJ IDEA helps you write your code and manage the application at runtime, see the next tutorial, which focuses on more advanced Spring support features.

Last modified: 02 June 2020