§The Play WS API

Sometimes you want to call other HTTP services from within a Play application. Play supports this via its play.libs.WS library, which provides a way to make asynchronous HTTP calls.

A call made by play.libs.WS should return a Promise<Ws.Response>, which you can handle later with Play’s asynchronous mechanisms.

§Making HTTP calls

To make an HTTP request, you start with WS.url() to specify the URL. Then you get a builder that you can use to specify HTTP options, such as setting headers. You end by calling a method corresponding to the HTTP method you want to use:

Promise<WS.Response> homePage = WS.url("http://mysite.com").get();

Alternatively:

Promise<WS.Response> result = WS.url("http://localhost:9001").post("content");

§Retrieving the HTTP response result

The call is made asynchronously and you need to manipulate it as a Promise<WS.Response> to get the actual content. You can compose several promises and end up with a Promise<Result> that can be handled directly by the Play server:

import play.libs.F.Function;
import play.libs.WS;
import play.mvc.*;

public class Controller extends Controller {

  public static Result feedTitle(String feedUrl) {
    return async(
      WS.url(feedUrl).get().map(
        new Function<WS.Response, Result>() {
          public Result apply(WS.Response response) {
            return ok("Feed title:" + response.asJson().findPath("title"));
          }
        }
      )
    );
  }
  
}

§Composing results

If you want to make multiple calls in sequence, this can be achieved using flatMap:

  public static Result feedComments(String feedUrl) {
    return async(
      WS.url(feedUrl).get().flatMap(
        new Function<WS.Response, Promise<Result>>() {
          public Promise<Result> apply(WS.Response response) {
            return WS.url(response.asJson().findPath("commentsUrl").get().map(
              new Function<WS.Response, Result>() {
                public Result apply(WS.Response response) {
                  return ok("Number of comments: " + response.asJson().findPath("count"));
                }
              }
            );
          }
        }
      )
    );
  }

§Configuring the HTTP client

The HTTP client can be configured globally in application.conf via a few properties:

# Follow redirects (default true)
ws.followRedirects=true
# Connection timeout in ms (default 120000)
ws.timeout=120000
# Whether to use http.proxy* JVM system properties (default true)
ws.useProxyProperties=true
# A user agent string to set on each request (default none)
ws.useragent="My Play Application"

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