Play Application Overview

Application Overview📌

We have implemented this tutorial as a simple Play application so that we can start learning about Play at ease.

Let's first look at what happens during runtime. This will give us a good Play application overview. When we enter http://localhost:9000/ in our browser:

💡 The browser fetches the root or URI from the HTTP server with the help of the GET method.

💡 The internal HTTP Server of Play receives the request and resolves the request with the help of the routes file, which maps URIs to the action methods of the controller.

💡 The action method displays the index page using pre-defined Twirl templates.

💡 The HTTP server returns the result as an HTML page.

At a higher level, the flow looks something like this:

Exploring the project to see the Play application overview📌

Next, let's have a look at the tutorial project. This will give us more clarity:

💡 The routes file (Routes file maps the request to the controller method).

💡💡 The controller action method( This method defines how to operate a request to the root URI).

The action method, called by the pre-defined Twirl template, renders the HTML markup.

Follow these steps to delve deep into the source files:

Note: For Windows shells, in the following procedures, we use '\' in place of '/' in path names (there is no need to change path names or URL, though).

Using a command window or GUI, we look at the contents of the top-level project directory. Application components are stored in the following directories.

💡 Directories for controllers and views are stored in the app subdirectory (it will be familiar to those who have some experience with the Model View Controller (MVC) architecture.) This simple project does not need any external data repository, and that's why it does not contain any models directory, but this is where we would add it. This will make our Play application overview more comprehensive.

💡 The public subdirectory stores directories for images, javascripts, and stylesheets.

💡 The conf directory stores the configuration of an application. 

To locate the controller action method, open the app/controllers/HomeController.java (or .scala) file with your favourite text editor. There is an index action method in the Homecontroller class, as shown below. This straightforward action method generates an HTML page from the index.scala.html Twirl template file.

<!--Java Code-->
public Result index() {
return ok(views.html.index.render("Your app is ready.", assetsFinder));
}


<!--Scala Code-->


def index = Action {
  Ok(views.html.index("Your new application is ready."))
}

Open the conf/routes file to display the route that maps the browser request to the controller method. A route is made up of an HTTP method, a path, and an action. This control over the URL scheme makes it easy to design clean, bookmarkable, human-readable URLs. We can map a GET request for the root URL or to the index action in HomeController using:
 

GET /         controllers.HomeController.index

Then open app/views/index.scala.html with your text editor. To generate the page, the primary directive in this file calls the main template main.scala.html with the string Welcome.

Frequently Asked Questions📌

What is the use of the Play framework?

Play Framework makes it convenient to develop web applications with Java & Scala. Play is based on a light, stateless, web-friendly architecture. Play is built on Akka. It provides predictable and minimal resource consumption (CPU, memory, threads) for highly-scalable applications.

What is Play?

The objective of Play is to be a general-purpose programming language which focuses on immutability and controlled side effects. This factor favors mutable data structures. Play is also targeting to be fully portable with the assistance of web assembly. In the future, we may see Play do all these things. 

What is MVC in the play framework?

A play application follows the MVC architectural pattern, which is applied to Web architecture. The primary goal of this architectural pattern is to split the application into two separate layers-the Presentation layer and the Model layer. The Presentation layer is further separated into a View and a Controller layer.

Conclusion📌

Congrats! You made it to the end of the article on Play Application Overview. Play Application Overview gives us clarity on how Play can be used without any complexity in developing web applications.

Here are a few key websites that will aid in this:

1. How to String parameter sets the page title
2. Anatomy of a Play Application.
3. Source Code
4. Documentation Guidelines
5. Community Forums

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