Javalin

Javalin is a very popular, simple, lightweight and flexible micro web framework for Java and Kotlin. It's un-opinionated and runs on top of Jetty, one of the most used and stable web-servers for the JVM.

Build configuration

Kilua RPC provides two different modules for Javalin:

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

• kilua-rpc-javalin-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-javalin:$kiluaRpcVersion")
//        implementation("dev.kilua:kilua-rpc-javalin-koin:$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 - Context , Javalin and WsContext (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.

class AddressService(val ctx: Context) : IAddressService {
    override suspend fun getAddressList(search: String?, sort: Sort) {
        println(ctx.req.remoteAddr)
        println(ctx.req.session.id)
        return listOf()
    }
}

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.

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.javalin.Javalin

fun main() {
    Javalin.create().start(8080).apply {
        initRpc {
            registerService<IAddressService> { AddressService() }
        }
        applyRoutes(getServiceManager<IAddressService>())
    }
}

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.javalin.Javalin
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 main() {
    Javalin.create().start(8080).apply {
        initRpc(AddressModule().module)
        applyRoutes(getServiceManager<IAddressService>())
    }
}

Security

When configuring security with AccessManager you can call applyRoutes with additional parameter containing roles.

enum class ApiRole : Role { AUTHORIZED, ANYONE }

fun main() {
    Javalin.create { config ->
        config.accessManager { handler, ctx, permittedRoles ->
            when {
                permittedRoles.contains(ApiRole.ANYONE) -> handler.handle(ctx)
                ctx.sessionAttribute<Profile>(SESSION_PROFILE_KEY) != null -> handler.handle(ctx)
                else -> ctx.status(HttpStatus.UNAUTHORIZED).json("Unauthorized")
            }
        }
    }.start(8080).apply {
        kvisionInit(ConfigModule(), DbModule())
        applyRoutes(getServiceManager<IAddressService>(), setOf(ApiRole.AUTHORIZED))
        applyRoutes(getServiceManager<IProfileService>(), setOf(ApiRole.AUTHORIZED))
        applyRoutes(getServiceManager<IRegisterProfileService>(), setOf(ApiRole.ANYONE))

        // Security config
        post("/login", { ctx ->
            val username = ctx.formParam("username") ?: ""
            val password = ctx.formParam("password") ?: ""
            transaction {
                UserDao.select {
                    (UserDao.username eq username) and (UserDao.password eq DigestUtils.sha256Hex(password))
                }.firstOrNull()?.let {
                    val profile =
                        Profile(it[UserDao.id], it[UserDao.name], it[UserDao.username].toString(), null, null)
                    ctx.sessionAttribute(SESSION_PROFILE_KEY, profile)
                    ctx.status(HttpStatus.OK)
                } ?: ctx.status(HttpStatus.UNAUTHORIZED)
            }
        }, setOf(ApiRole.ANYONE))
        get("/logout", { ctx ->
            ctx.req().session.invalidate()
            ctx.redirect("/", HttpStatus.FOUND)
        }, setOf(ApiRole.AUTHORIZED))
    }
}