Kert is a concise HTTP, GRPC and GraphQL library for Kotlin. It's not an Android library, it's a JVM library for backend development.
Compare to the official gRPC-Java, Kert provides the benefits like:
- No need for 2 separate libraries / ports to serve HTTP and GRPC requests.
- Simply to use HTTP health check in Kubernetes.
- Coroutine / Flow based interface more intuitive for async processing and context propagation.
- Simple filter & interceptor interface for async handling.
Server Example:
val server = httpServer(8080) {
// http filter
filter { req, next ->
println("Serving request ${req.path}")
next(req)
}
// http service
router {
// http request handler
get("/ping") {
response(body = "pong")
}
}
// grpc service
grpc {
// enable server reflection
serverReflection = true
// grpc interceptor
interceptor( object : GrpcInterceptor {
override suspend fun <REQ, RESP> invoke(method: MethodDescriptor<REQ, RESP>, req: GrpcRequest<REQ>, next: GrpcHandler<REQ, RESP>): GrpcResponse<RESP> {
// intercept the request
if (req.metadata["authentication"] == null) throw IllegalArgumentException("Authentication header is missing")
// intercept each message in the streaming request
val filteredReq = req.copy(messages = req.messages.map {
println(it)
it
})
return next(method, filteredReq)
}
})
// register service implementation
service(EchoServiceImpl())
}
// GraphQL
graphql {
playground = true
schema {
config {
supportedPackages = listOf("<your package name>")
}
query(MyExampleQuery())
}
}
}
server.start()Client Example:
// http request
val client = httpClient {
options {
defaultHost = "localhost"
defaultPort = 8551
protocolVersion = HttpVersion.HTTP_2
}
// a client side filter to set authorization header in request
filter { req, next ->
req.headers["authorization"] = "my-authorization-header"
next(req)
}
}
client.get("ping")
// grpc request
val stub = EchoGrpcKt.stub(client)
stub.unary(EchoReq.newBuilder().setId(1).setValue("hello").build())