Routing and Controllers

Creating controllers

As our application grows, we will need to organise our code. Do do this, we can create controller classes.

The controller classes can accept the ctx object passed by Javalin.

public class UserController {
  public static void getAllUsers(Context ctx) {
    var users = UserRepository.findAll();
    ctx.json(users);
  }
}

Attaching controllers

We can attach the controllers to the Javalin app like this:

public class App {

  public static void main(String[] args) {
    var app = createApp();
    app.start(5000);
  }

  public static Javalin createApp() {
    var app = Javalin.create();

    app.get("/users", UserController::getAllUsers);
    app.get("/users/{id}", UserController::getUserById);
    app.post("/users", UserController::createUser);

    return app;
  }
}

API Builder

We repeat the /users endpoint quite often. Perhaps a neater way to arrange this is to use Javalin's apiBuilder:

import static io.javalin.apibuilder.ApiBuilder.*;

Now we can nest routes.

public static Javalin createApp() {
  var app = Javalin.create(config -> {

    config.router.apiBuilder(() -> {
      path("/users", () -> {
        get("", UserController::getAllUsers);
        get("/{id}", UserController::getUserById);
        post("", UserController::createUser);
      });
    });

  });

  return app;
}

It becomes a bit easier to refactor the URL structure if needed.