Akka HTTP Java API: Need to create a ContentType from a string MIME type

This might just be a documentation issue. I’ve googled, I’ve search the Akka HTTP docs, and I’ve poked through the code.

A pointer—or code—would be awesome.

I have a String MIME type (such as “application/jar”). I want to create a ContentType for use in a response. I only care about a binary type, as this mapping is for a download only.

I’m stuck with the Java API. (Don’t ask.) I can easily create a mapping from a String to a MediaType. I cannot, for the life of me, figure out how—in Java—to make the final leap from a MediaType to a ContentType.

Is this even possible, without resorting to the Scala API? My client would prefer that there be no Scala in this server.

Brian Clapper

Hi Brian,

Would something like this work for you? https://doc.akka.io/japi/akka-http/current/akka/http/javadsl/model/ContentTypes.html#parse-java.lang.String-

You should be able to pass any valid ContentType string as defined in the spec.
Here you can find the Mozilla page for it :slight_smile: https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Type


Ah, you’re awesome Josep :slight_smile:
I was looking into this from the pessimistic angle and found that we do not have a 1:1 mirror of the following Scala DSL style:

  private val custom: MediaType.Binary = MediaType.customBinary("application", "wat", MediaType.Compressible)
  private val binary = ContentType(custom)
  println(s"binary = ${binary}")

This has a few missing methods in Java DSL it seems (or I’m tired).
The parse should be good enough indeed, along with https://doc.akka.io/docs/akka-http/current/common/http-model.html#registering-custom-media-types but perhaps worth a ticket to make my example be 1:1 copiable to Java as well, WDYT Josep (or did I miss some API)?

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You’re right, there is no 1:1.

However, there is a close match: https://doc.akka.io/japi/akka-http/current/akka/http/javadsl/model/MediaTypes.html#applicationBinary-java.lang.String-boolean-java.lang.String…- and co.
With those methods you would get a MediaType which then can be used in https://doc.akka.io/japi/akka-http/current/akka/http/javadsl/model/ContentTypes.html#create-akka.http.javadsl.model.MediaType.Binary- and others.

We could have a ticket to extend the Java API with such a factory method.

@jlprat Perfect. Thanks.

I wondered why I missed it. Then, I determined that I was using Akka HTTP 10.0.11, which doesn’t have ContentTypes.parse(). I had drilled into ContentTypes via the IDE.

My bad for not checking my version.

Thanks again.


You are welcome!

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Yeah, agreed. Can you open a ticket about it? Thanks a ton

Sure! Will do :+1:


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