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§Actions, Controllers and Results

§What is an Action?

Most of the requests received by a Play application are handled by an action.

An action is basically a Java method that processes the request parameters, and produces a result to be sent to the client.

public Result index() {
    return ok("Got request " + request() + "!");
}

An action returns a play.mvc.Result value, representing the HTTP response to send to the web client. In this example ok constructs a 200 OK response containing a text/plain response body.

§Controllers

A controller is nothing more than a class extending play.mvc.Controller that groups several action methods.

package controllers;

import play.*;
import play.mvc.*;

public class Application extends Controller {

    public Result index() {
        return ok("It works!");
    }

}

The simplest syntax for defining an action is a method with no parameters that returns a Result value, as shown above.

An action method can also have parameters:

public Result index(String name) {
    return ok("Hello " + name);
}

These parameters will be resolved by the Router and will be filled with values from the request URL. The parameter values can be extracted from either the URL path or the URL query string.

§Results

Let’s start with simple results: an HTTP result with a status code, a set of HTTP headers and a body to be sent to the web client.

These results are defined by play.mvc.Result, and the play.mvc.Results class provides several helpers to produce standard HTTP results, such as the ok method we used in the previous section:

public Result index() {
    return ok("Hello world!");
}

Here are several examples that create various results:

Result ok = ok("Hello world!");
Result notFound = notFound();
Result pageNotFound = notFound("<h1>Page not found</h1>").as("text/html");
Result badRequest = badRequest(views.html.form.render(formWithErrors));
Result oops = internalServerError("Oops");
Result anyStatus = status(488, "Strange response type");

All of these helpers can be found in the play.mvc.Results class.

§Redirects are simple results too

Redirecting the browser to a new URL is just another kind of simple result. However, these result types don’t have a response body.

There are several helpers available to create redirect results:

public Result index() {
    return redirect("/user/home");
}

The default is to use a 303 SEE_OTHER response type, but you can also specify a more specific status code:

public Result index() {
    return temporaryRedirect("/user/home");
}

Next: HTTP routing