# Play Framework
###### source: [Play Framework 2.5 Documentation](https://www.playframework.com/documentation/2.5.x/JavaHome)
## Actions, Controllers, Results
Requests received by a Play application is handled by an **action** (Java method), and it returns a **Result**.

A **controller** class groups several action methods.

## Routing
Play recommends dependency-injection routers (and controllers), as opposed to static routers.

Routes are defined in `conf/routes/`

### Dynamic route path

GET    /client/:id    controllers.Clients.show(id: Long)

### Dynamic route path with regex

GET    /items/$id<[0-9]+>    controllers.Items.show(id: Long)

### Reversing URL

public class Application extends Controller{
    public Result hello(String name){
        return ok("Hello "+name);
    }
//Redirects to /hello/Bob
    public Result index(){
        return redirect(controllers.routes.Application.hello("Bob"));
    }
}

## Request
### Body Parser
Default body parser parses `application/json` body as a `JsonNode`, and an `application/x-www-form-urlencoded` as a `Map<String, String[]>`.

Accessing the request body is as follows:

public Result index(){
    JsonNode json = request().body().asJson();
    return ok("Name is: "+json.get("name").asText());
}

## Response
### Setting HTTP Response Headers

public Result index(){
    response().setHeader(CACHE_CONTROL, "max_age=3600");
    response().setHeader(ETAG,"xxx");
    return ok("<h1>Hello world!</h1>").as("text/html");
}

### Setting Cookies

response().setCookie("cookie1_value","cookie2_value");

## Asynchronous HTTP Handling
Asynchronous requests are handled using a promise API, `CompletionStage<Result>`, which, when redeemed, returns the `Result` object.

Actions are asynchronous by default (`Result`s are internally enclosed in a promise).
### Sending Async Results

public CompletionStage<Result> index(){
    return CompletableFuture
    .supplyAsync(()-> intensiveComputation())
    .thenApply(i-> ok("result: "+i));
}