Encoding / Decoding
The HTTP spec defines a Content-Encoding
header, which signifies whether the entity body of an HTTP message is “encoded” and, if so, by which algorithm. The only commonly used content encodings are compression algorithms.
Currently, Apache Pekko HTTP supports the compression and decompression of HTTP requests and responses with the gzip
or deflate
encodings. The core logic for this lives in the org.apache.pekko.http.scaladsl.coding
package.org.apache.pekko.http.javadsl.coding.Coder
enum class.
Server side
The support is not enabled automatically, but must be explicitly requested. For enabling message encoding/decoding with Routing DSL see the CodingDirectives.
Usually, it suffices to surround routes that should support response encoding by the encodeResponse directive, and routes that should support request decoding by the decodeRequest directive. Those directives will automatically and transparently enable support for encodings and negotiating which encoding to use out of the default encodings supported. The set of predefined MediaTypes
MediaTypes
contains a hint whether content of a given media type would benefit from compression.
Client side
There is currently no high-level or automatic support for decoding responses on the client-side.
The following example shows how to decode responses manually based on the Content-Encoding
header:
- Scala
-
source
import org.apache.pekko import pekko.actor.ActorSystem import pekko.http.scaladsl.Http import pekko.http.scaladsl.coding.Coders import pekko.http.scaladsl.model._, headers.HttpEncodings import scala.concurrent.Future implicit val system = ActorSystem() implicit val ec: ExecutionContext = system.dispatcher val http = Http() val requests: Seq[HttpRequest] = Seq( "https://httpbin.org/gzip", // Content-Encoding: gzip in response "https://httpbin.org/deflate", // Content-Encoding: deflate in response "https://httpbin.org/get" // no Content-Encoding in response ).map(uri => HttpRequest(uri = uri)) def decodeResponse(response: HttpResponse): HttpResponse = { val decoder = response.encoding match { case HttpEncodings.gzip => Coders.Gzip case HttpEncodings.deflate => Coders.Deflate case HttpEncodings.identity => Coders.NoCoding case other => log.warning(s"Unknown encoding [$other], not decoding") Coders.NoCoding } decoder.decodeMessage(response) } val futureResponses: Future[Seq[HttpResponse]] = Future.traverse(requests)(http.singleRequest(_).map(decodeResponse)) futureResponses.futureValue.foreach { resp => system.log.info(s"response is ${resp.toStrict(1.second).futureValue}") } system.terminate()
- Java
-
source
import org.apache.pekko.actor.ActorSystem; import org.apache.pekko.http.javadsl.Http; import org.apache.pekko.http.javadsl.coding.Coder; import org.apache.pekko.http.javadsl.model.HttpRequest; import org.apache.pekko.http.javadsl.model.HttpResponse; import org.apache.pekko.http.scaladsl.model.headers.HttpEncodings; import java.util.Arrays; import java.util.List; import java.util.concurrent.CompletableFuture; import java.util.concurrent.CompletionStage; import java.util.function.Function; import java.util.stream.Collectors; public class HttpClientDecodingExampleTest { public static void main(String[] args) throws Exception { final ActorSystem system = ActorSystem.create(); final List<HttpRequest> httpRequests = Arrays.asList( HttpRequest.create("https://httpbin.org/gzip"), // Content-Encoding: gzip in response HttpRequest.create( "https://httpbin.org/deflate"), // Content-Encoding: deflate in response HttpRequest.create("https://httpbin.org/get") // no Content-Encoding in response ); final Http http = Http.get(system); final Function<HttpResponse, HttpResponse> decodeResponse = response -> { // Pick the right coder final Coder coder; if (HttpEncodings.gzip().equals(response.encoding())) { coder = Coder.Gzip; } else if (HttpEncodings.deflate().equals(response.encoding())) { coder = Coder.Deflate; } else { coder = Coder.NoCoding; } // Decode the entity return coder.decodeMessage(response); }; List<CompletableFuture<HttpResponse>> futureResponses = httpRequests.stream() .map(req -> http.singleRequest(req).thenApply(decodeResponse)) .map(CompletionStage::toCompletableFuture) .collect(Collectors.toList()); for (CompletableFuture<HttpResponse> futureResponse : futureResponses) { final HttpResponse httpResponse = futureResponse.get(); system .log() .info( "response is: " + httpResponse.entity().toStrict(1000, system).toCompletableFuture().get()); } system.terminate(); } }