Create your Spring Controller

Now we have our functioning Spring project we need to create a Spring Controller to handle the web requests.

Create our Controller

One important thing to note here is that you don't need to tell your Spring Application class about your (new) Spring Controller class. That is handled by the @SpringBootApplication annotation in the Application class which also consists of other annotations, including @ComponentScan. This means that the current package, and sub packages will be scanned for Spring components. It's a little unnerving when you first start using Spring but in time you'll get used to it once you have an appreciation of what Spring is doing behind the scenes for you.

1. Create a new Java class in the same place as your HelloWorldApplication.java class called HelloWorldController.java.

2. The first thing we need to do is tell Spring that this is a REST Controller, so you need to add a class level annotation of @RestController. This annotation means this class will be picked up by the component scan, because it's in the same package as our Application class. Our REST Controller, HelloWorldController, will therefore be available from the application context.

3. The next step is to create a method that will tell Spring that if we go the root of our webserver, we would like to see the string Hello World from Spring Boot. To do that we need to add a method with a @RequestMapping annotation like our helloWorld one here:

package com.example.helloworld;

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

@RestController
public class HelloWorldController {

  @RequestMapping("/")
  public String helloWorld(){
    return "Hello World from Spring Boot";
  }
}

4. Now we need to re-run our Spring application. You might need to stop it first if it's still running from the previous step. You can run it again with ⌃R (macOS) / Shift+F10 (Windows/Linux).

5. When you go to the browser, enter the following URL localhost:8080. You should see your text being returned:

6. Assuming that's working correctly, you can start to get more adventurous. Try adding this new code below your first method:

@RequestMapping("/goodbye")
public String helloWorld(){
  return "Goodbye from Spring Boot";
}

7. Now run your application again. At the root you should still see Hello World from Spring Boot because the @RequestMapping is / indicating root. However, if you now type in localhost:8080/goodbye, you should see Goodbye from Spring Boot.

That's it! You're done, congratulations on creating your first Spring Application and serving some text in the browser! In the next section we'll create a test for our application.