Ktor Global-Call-Data

Description

This Ktor-Feature allows to access the call Object from any suspending function that was called by the route (e.g. get() or post()) No passthrough of the variable required any more!

This Feature also allows specifying more attributes that should be bound to the rest call. Examples are

• A Unique Call-ID for each call
• A Call specific Logging-Object that should be added to the database after the request is done
• ...

Disclaimer

If anything is unclear, feel free to

• open an issue
• text me on twitter @byCaelis
• text me via email github@maax.gr

Installation

Add the jitpack repository to build.gradle

repositories {
    ...
    maven { url "https://jitpack.io" }
}

Add ktor-globalcalldata dependency to build.gradle.

dependencies {
    ...
    implementation 'com.github.MaaxGr:ktor-globalcalldata:1.0.2'
}

Install Feature

install(GlobalCallData)

Example 1: Getting Started

Configure routing block

Set up a route, that calls a suspending function! The test() function can be in any class

routing {
    get("/test") {
        test()
        call.respond("OK")
    }
}

Access callData() to get call data

Call the callData() from any suspending function, that was called by a defined above.

suspend fun test() {
    val url = callData().call.request.uri
    println(url) // prints "/test"
}

If call is null test() method was probably called from the wrong coroutine!

Example 2: Define custom global data

Define custom Key

Each CallData has an own key. In this example we create a key named CallUUID which value can be of type UUID. You can specify a differt Key-Name or value in the generic. It is important, that the Key is an object

object CallUUID : Key<UUID>

Define class that inherits from CallData

Define a class that inherits from CallData and pass the CoroutineContext from the constructor. Now add a delegated variable for each property you want to have globally accessible for the current call.

class CustomCallData(context: CoroutineContext) : CallData(context) {
    var callUUID: UUID by delegate.propNotNull(CallUUID)
}

Create method to access CustomCallData

Declare the method in a file on the top level to access it globally!

suspend fun customCallData() = CustomCallData(coroutineContext)

Import the coroutineContext from kotlin.coroutines.coroutineContext

Define route

get("/test") {
    a()
    b()
    call.respond("OK")
}

Define method that stores the Call-UUID

suspend fun a() {
    customCallData().callUUID = UUID.randomUUID()
}

Define a method that accesses the Call-UUID

suspend fun b() {
    val uuid = customCallData().callUUID
    println(uuid) // prints "b0518030-e85b-4991-9105-9520fea931cc"
}

FAQ

To be continued!