Implement First Service

  1. Implement the first simple endpoint

    1. Create AccountController.java

    Create a new directory in the directory src/main/java/com/example/accounts called controller. In that new directory, create a new Java file called AccountController.java. When prompted for the type, choose class.

    Your new file should look like this:

    package com.example.accounts.controller;

public class AccountController {

}
    1. Add the RestController annotation

    Add the RestController annotation to this class to tell Spring Boot that we want this class to expose REST services. You can just start typing @RestController before the public class statement and Visual Studio Code will offer code completion for you. When you select from the pop-up, Visual Studio Code will also add the import statement for you. The list of suggestions is based on the dependencies you added to your project.

    Add the RequestMapping annotation to this class as well, and set the URL path to /api/v1. Your class should now look like this:

    package com.example.accounts.controller;

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

@RestController
@RequestMapping("/api/v1")
public class AccountController {

}
    1. Add ping method

    Add a method to this class called ping which returns a String with a helpful message. Add the GetMapping annotation to this method and set the URL path to /hello. Your class should now look like this:

    package com.example.accounts.controller;

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

@RestController
@RequestMapping("/api/v1")
public class AccountController {

  @GetMapping("/hello")
  public String ping() {
    return "Hello from Spring Boot";
  }

}

    You have just implemented your first REST service in Spring Boot! This service will be available on http://localhost:8080/api/v1/hello. And the GetMapping annotation tells Spring Boot that this service will respond to the HTTP GET method.

    You can test your service now by building and running again. Make sure you save the file. If you still have the application running from before, hit Ctrl+C (or equivalent) to stop it, and then build and run with this command:

    $ mvn spring-boot:run

    Then try to call your service with this command:

    $ curl -i http://localhost:8080/api/v1/hello
HTTP/1.1 200 
Content-Type: text/plain;charset=UTF-8
Content-Length: 22
Date: Sat, 25 Feb 2023 17:59:52 GMT

Hello from Spring Boot

    Great, it works! Notice it returned HTTP Status Code 200 (OK) and some HTTP Headers along with the body which contained your message. Later we will see how to return JSON and to set the status code appropriately.