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Kotlin quick start updates (#466) 

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@ -1,6 +1,7 @@
--- ---
title: Quick start title: Quick start
description: This guide gets you started with gRPC in Kotlin with a simple working example. description: This guide gets you started with gRPC in Kotlin with a simple working example.
spelling: cSpell:ignore println
weight: 10 weight: 10
--- ---
@ -9,21 +10,24 @@ weight: 10
- [Kotlin][] version 1.3 or higher - [Kotlin][] version 1.3 or higher
- JDK version 7 or higher - JDK version 7 or higher
### Download the example ### Get the example code
You'll need a local copy of the example code to work through this quick start. The example code is part of the [grpc-kotlin][] repo.
Download the example code from our GitHub repository (the following command
clones the entire repository, but you just need the examples for this quick start 1. [Download the repo as a zip file][download] and unzip it, or clone
and other tutorials): the repo:
```sh ```sh
# Clone the repository at the latest release to get the example code:
$ git clone https://github.com/grpc/grpc-kotlin $ git clone https://github.com/grpc/grpc-kotlin
# Navigate to the examples: ```
2. Change to the examples directory:
```sh
$ cd grpc-kotlin/examples $ cd grpc-kotlin/examples
``` ```
### Run a gRPC application ### Run the example
From the `examples` directory: From the `examples` directory:
@ -36,29 +40,29 @@ From the `examples` directory:
2. Run the server: 2. Run the server:
```sh ```sh
$ ./build/install/examples/bin/hello-world-server $ ./server/build/install/server/bin/hello-world-server
Server started, listening on 50051
``` ```
3. From another terminal, run the client: 3. From another terminal, run the client:
```sh ```sh
$ ./build/install/examples/bin/hello-world-client $ ./client/build/install/client/bin/hello-world-client
Received: Hello world
``` ```
Congratulations! You've just run a client-server application with gRPC. Congratulations! You've just run a client-server app with gRPC.
### Update a gRPC service ### Update the gRPC service
Now let's look at how to update the application with an extra method on the In this section, you'll update the app with an extra server method. The app's
server for the client to call. Our gRPC service is defined using [Protocol gRPC service, named `Greeter`, is defined using [protocol buffers][pb]. To learn
Buffers][pb]; you can find out lots more about how to define a service in a more about how to define a service in a `.proto` file, see [Basics tutorial][].
`.proto` file in [Basics tutorial](../basics/). For now For now, all you need to know is that both the server and the client stub have a
all you need to know is that both the server and the client "stub" have a
`SayHello()` RPC method that takes a `HelloRequest` parameter from the client `SayHello()` RPC method that takes a `HelloRequest` parameter from the client
and returns a `HelloReply` from the server, and that this method is defined like and returns a `HelloReply` from the server, and that the method is defined like
this: this:
```protobuf ```protobuf
// The greeting service definition. // The greeting service definition.
service Greeter { service Greeter {
@ -76,9 +80,10 @@ message HelloReply {
string message = 1; string message = 1;
} }
``` ```
Let's update this so that the `Greeter` service has two methods. Edit
`src/main/proto/hello_world.proto` and update it with a new `SayHelloAgain()` Open `helloworld/hello_world.proto` from the
method, with the same request and response types: [protos/src/main/proto/io/grpc/examples][protos-src] folder, and add a
new `SayHelloAgain()` method, with the same request and response types:
```protobuf ```protobuf
// The greeting service definition. // The greeting service definition.
@ -102,21 +107,21 @@ message HelloReply {
Remember to save the file! Remember to save the file!
### Update and run the application ### Update the app
When we recompile the example, normal compilation will regenerate When you build the example, the build process regenerates `HelloWorldGrpcKt.kt`,
`HelloWorldGrpcKt.kt`, which contains our generated gRPC client and server classes. which contains the generated gRPC client and server classes. This also
This also regenerates classes for populating, serializing, and retrieving our regenerates classes for populating, serializing, and retrieving our request and
request and response types. response types.
However, we still need to implement and call the new method in the human-written However, you still need to implement and call the new method in the
parts of our example application. hand-written parts of the example app.
#### Update the server #### Update the server
In the same directory, open Open `helloworld/HelloWorldServer.kt` from the
`src/main/kotlin/io/grpc/examples/helloworld/HelloWorldServer.kt`. Implement the [server/src/main/kotlin/io/grpc/examples][server-src] folder. Implement the new
new method like this: method like this:
```kotlin ```kotlin
private class HelloWorldService : GreeterGrpcKt.GreeterCoroutineImplBase() { private class HelloWorldService : GreeterGrpcKt.GreeterCoroutineImplBase() {
@ -134,22 +139,22 @@ private class HelloWorldService : GreeterGrpcKt.GreeterCoroutineImplBase() {
#### Update the client #### Update the client
In the same directory, open Open `helloworld/HelloWorldClient.kt` from the
`src/main/kotlin/io/grpc/examples/helloworld/HelloWorldClient.kt`. Call the new [client/src/main/kotlin/io/grpc/examples][client-src] folder. Call the new
method like this: method like this:
```kotlin ```kotlin
class HelloWorldClient constructor( class HelloWorldClient(
private val channel: ManagedChannel private val channel: ManagedChannel
) : Closeable { ) : Closeable {
private val stub: GreeterCoroutineStub = GreeterCoroutineStub(channel) private val stub: GreeterCoroutineStub = GreeterCoroutineStub(channel)
suspend fun greet(name: String) = coroutineScope { suspend fun greet(name: String) {
val request = HelloRequest.newBuilder().setName(name).build() val request = HelloRequest.newBuilder().setName(name).build()
val response = async { stub.sayHello(request) } val response = stub.sayHello(request)
println("Received: ${response.await().message}") println("Received: ${response.message}")
val againResponse = async { stub.sayHelloAgain(request) } val againResponse = stub.sayHelloAgain(request)
println("Received: ${againResponse.await().message}") println("Received: ${againResponse.message}")
} }
override fun close() { override fun close() {
@ -158,7 +163,7 @@ class HelloWorldClient constructor(
} }
``` ```
#### Run! ### Run the updated app
Run the client and server like you did before. Execute the following commands Run the client and server like you did before. Execute the following commands
from the `examples` directory: from the `examples` directory:
@ -172,19 +177,15 @@ from the `examples` directory:
2. Run the server: 2. Run the server:
```sh ```sh
$ ./build/install/examples/bin/hello-world-server $ ./server/build/install/server/bin/hello-world-server
Server started, listening on 50051
``` ```
3. From another terminal, run the client. This time, add a name as a 3. From another terminal, run the client. This time, add a name as a
command-line argument: command-line argument:
```sh ```sh
$ ./build/install/examples/bin/hello-world-client Alice $ ./client/build/install/client/bin/hello-world-client Alice
```
You'll see the following output:
```nocode
Received: Hello Alice Received: Hello Alice
Received: Hello again Alice Received: Hello again Alice
``` ```
@ -193,8 +194,14 @@ from the `examples` directory:
- Learn how gRPC works in [Introduction to gRPC](/docs/what-is-grpc/introduction/) - Learn how gRPC works in [Introduction to gRPC](/docs/what-is-grpc/introduction/)
and [Core concepts](/docs/what-is-grpc/core-concepts/). and [Core concepts](/docs/what-is-grpc/core-concepts/).
- Work through the [Basics tutorial](../basics/). - Work through the [Basics tutorial][].
- Explore the [API reference](../api). - Explore the [API reference](../api).
[Basics tutorial]: ../basics/
[download]: https://github.com/grpc/grpc-kotlin/archive/master.zip
[grpc-kotlin]: https://github.com/grpc/grpc-kotlin
[Kotlin]: https://kotlinlang.org [Kotlin]: https://kotlinlang.org
[pb]: https://developers.google.com/protocol-buffers [pb]: https://developers.google.com/protocol-buffers
[client-src]: https://github.com/grpc/grpc-kotlin/tree/master/examples/client/src/main/kotlin/io/grpc/examples
[protos-src]: https://github.com/grpc/grpc-kotlin/tree/master/examples/protos/src/main/proto/io/grpc/examples
[server-src]: https://github.com/grpc/grpc-kotlin/tree/master/examples/server/src/main/kotlin/io/grpc/examples