TL;DR: Is it possible to do streaming decoding of ...

# ktor

[Deepak Nulu]

TL;DR: Is it possible to do streaming decoding of JSON in Ktor server and client? I need it to be similar to javax.json.stream.JsonParser where I get to handle the lexer tokens the way I want.

I am developing a multi-platform library that is currently JVM-only since it uses java.io.Reader and java.io.Writer. It also uses javax.json.stream.JsonParser to parse JSON as it streams in. I currently cannot use kotlinx.serialization for decoding since I have a specific representation in JSON that is not suitable for kotlinx.serialization.

I currently use my library in a Ktor-based server to convert JSON in POST requests as they stream in. I also need to use my library on the client side to convert JSON in responses as they stream in. So I want to make my library a multi-platform library so that I can use it on the server side (Kotlin/JVM) as well as the client side (Kotlin/JS).

I went looking for java.io.Reader replacements that are multi-platform. I narrowed it down to Okio and Ktor’s ByteReadChannel. I would prefer to use Ktor since it is from JetBrains, and also because I can use it on both the client and the server (Okio is only client side).

The next thing I went looking for is a multi-platform streaming JSON decoder. I found some classes in kotlinx.serialization and I see that it is supported for Okio. I could be wrong, but I did not find it supported for Ktor’s ByteReadChannel.

[Aleksei Tirman [JB]]

The problem is that java.io.Reader and classes from Okio provide blocking I/O but Ktor uses non-blocking one. We have the general-purpose asynchronous multiplatform I/O library in development but there is no ETA yet. You are right about integration between kotlinx.serialization and Okio libraries https://github.com/Kotlin/kotlinx.serialization/releases/tag/v1.4.0-RC.

[jw]

Okio is not just for clients

[Deepak Nulu]

Thank you @jw for responding! You’re right, Okio can be used on the server since it is multi-platform. I confused it with Okhttp when I was writing my message. Since I am already using Ktor on the server side, I was hoping there was a solution with Ktor itself.

[jw]

okhttp also works great on servers, for what it's worth

[Deepak Nulu]

@jw how do I use okhttp on the server? Do I replace ktor? Is okhttp client multiplatform (I need JS support)?

[Deepak Nulu]

Thank you @Aleksei Tirman [JB] for responding! I did not realize that okio is blocking (just started looking into it yesterday afternoon).

[Deepak Nulu]

@jw I probably misunderstood you when you said okhttp can be used on the server side. I thought you meant that I can use it as the server. I am now guessing you meant that it can be used on the server as an http client to talk to external dependencies of the server.