A simple RESTful Web Service

In the previous post, I have created a very simple WebApp using Spring Boot. Even if it works fine, it isn't much of a fun, giving no feedback whasoever to the user. Let's add a first basic web service to it.

In the Spring jargon, we want a REST Controller, so I create a new subpackage named controller below the one containing the application class, and in there I put a class, GreetingController, that is going to perform the mapping between the URI and the service, and return the expected resource.

The beauty of the Spring implementation is that I create a plain class, called a Bean, not to be confused with Java Bean nor Enterprise Java Bean, and I just annotate the class as @RestController and the method as @RequestMapping:

@RestController
public class GreetingController {
    @RequestMapping("/greeting")
    public String greeting() {
        return "Hello!";
    }
}

That's it. Springs takes care of all the boring details, and lets Tomcat answer generating a document that contains only "Hello" to a request address to the greeting address.

To test if this is working as expected, we can now start the project from the Boot Dashboard, and then accessing the resource from the internal browser, or from an external one. In any case the result should be something like this:

If you wonder why and how I'm using a non-standard Tomcat port, please refer to the previous post.

Sure you can run the application outside STS. Calling maven on the package target would let it generate a jar named something like hello-0.0.1-SNAPSHOT.jar in the target folder, than you can run it with the java -jar command.

Source code is on github. The only relevant change from the previous version is the GreetingController.