Ktor

Ktor is the asynchronous web framework for Kotlin created by JetBrains. It is written in Kotlin and its machinery and API is utilizing Kotlin coroutines. It's unopinionated design makes it a very good choice for development of applications composed of many different technologies.

Build configuration

Kilua RPC provides two different modules for Ktor:

• kilua-rpc-ktor, which doesn't use dependency injection (DI) and requires manual services registration,

• kilua-rpc-ktor-koin, which uses Koin dependency injection framework to access services implementations.

You need to add one of these modules to your project.

val commonMain by getting {
    dependencies {
        implementation("dev.kilua:kilua-rpc-ktor:$kiluaRpcVersion")
//        implementation("dev.kilua:kilua-rpc-ktor-koin:$kiluaRpcVersion")
    }
}

Service implementation

Service class

The implementation of the service class comes down to implementing required interface methods.

class AddressService : IAddressService {
    override suspend fun getAddressList(search: String?, sort: Sort) {
        return listOf()
    }
    override suspend fun addAddress(address: Address) {
        return Address()
    }
    override suspend fun updateAddress(id: Int, address: Address) {
        return Address()
    }
    override suspend fun deleteAddress(id: Int) {
        return false
    }
}

You can use @Factory annotation, if you use Koin and koin-annotations to configure dependency injection.

@Factory
class AddressService : IAddressService {
    // ...
}

Injecting server objects

You can use constructor parameters to inject server objects - ApplicationCall and WebSocketServerSession (see Websockets chapter) into your service classes. These objects give you access to the application configuration, its state, the current request and the user session (if it is configured).

class AddressService(val call: ApplicationCall) : IAddressService {
    override suspend fun getAddressList(search: String?, sort: Sort) {
        println(call.application.environment.config.propertyOrNull("option1")?.getString())
        println(call.application.attributes)
        println(call.request.uri)
        println(call.request.queryParameters["param1"])
        println(call.sessions)
        return listOf()
    }
}

Blocking code

Since Ktor architecture is asynchronous and non-blocking, you should never block a thread in your application code. If you have to use some blocking code (e.g. blocking I/O, JDBC) always use the dedicated coroutine dispatcher.

class AddressService : IAddressService {
    override suspend fun getAddressList(search: String?, sort: Sort) {
        return withContext(Dispatchers.IO) {
            retrieveAddressesFromDatabase(search, sort)
        }
    }
}

Application configuration

The main function

This function is the application starting point. It's used to initialize and configure application modules and features. Minimal implementation for Kilua RPC integration contains initRpc and applyRoutes function calls. initRpc function should be executed as last.

When using manual service registration, you call initRpc with a lambda function, which binds interfaces with their implementations. Different overloads of registerService function allow injecting server objects into your service classes.

import dev.kilua.rpc.applyRoutes
import dev.kilua.rpc.getServiceManager
import dev.kilua.rpc.initRpc
import dev.kilua.rpc.registerService
import io.ktor.server.application.*
import io.ktor.server.plugins.compression.*
import io.ktor.server.routing.*
import io.ktor.server.websocket.*

fun Application.main() {
    install(Compression)
    install(WebSockets)
    routing {
        applyRoutes(getServiceManager<IAddressService>())
    }
    initRpc {
        registerService<IAddressService> { AddressService() }
//        registerService<IAddressService> { call -> AddressService(call) }
//        registerService<IAddressService> { call, wsss -> AddressService(call, wsss) }
    }
}

When using Koin, you call initRpc with a list of Koin modules. Constructor parameter injection is automatically supported by Koin.

import dev.kilua.rpc.applyRoutes
import dev.kilua.rpc.getServiceManager
import dev.kilua.rpc.initRpc
import io.ktor.server.application.*
import io.ktor.server.plugins.compression.*
import io.ktor.server.routing.*
import io.ktor.server.websocket.*
import org.koin.core.annotation.ComponentScan
import org.koin.core.annotation.Module
import org.koin.ksp.generated.module

@Module
@ComponentScan
class AddressModule

// val addressModule = module {             // manual Koin module declaration
//    factoryOf(::AddressService)
// }
    
fun Application.main() {
    install(Compression)
    install(WebSockets)
    routing {
        applyRoutes(getServiceManager<IAddressService>())
    }
    initRpc(AddressModule().module)
}

Security

When using authentication plugin you can choose different security options for different services by calling applyRoutes in different contexts.

fun Application.main() {
    install(Authentication) {
        form {
            userParamName = "username"
            passwordParamName = "password"
            validate { credentials ->
                // ...
            }
            skipWhen { call -> call.sessions.get<Profile>() != null }
        }
    }

    routing {
        applyRoutes(getServiceManager<IRegisterProfileService>()) // No authentication needed
        authenticate {
            post("login") {
                // ...
            }
            get("logout") {
                call.sessions.clear<Profile>()
                call.respondRedirect("/")
            }
            applyRoutes(getServiceManager<IAddressService>()) // Authentication needed
            applyRoutes(getServiceManager<IProfileService>()) // Authentication needed
        }
    }
    initRpc {
       // ...
    }
}