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Kotlin quick start updates (#466) 

Contributes to #465
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content/docs/languages/kotlin/quickstart.md
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@ -1,6 +1,7 @@
---
title: Quick start
description: This guide gets you started with gRPC in Kotlin with a simple working example.
spelling: cSpell:ignore println
weight: 10
---
@ -9,21 +10,24 @@ weight: 10
- [Kotlin][] version 1.3 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.
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
and other tutorials):
The example code is part of the [grpc-kotlin][] repo.
```sh
# Clone the repository at the latest release to get the example code:
$ git clone https://github.com/grpc/grpc-kotlin
# Navigate to the examples:
$ cd grpc-kotlin/examples
```
1. [Download the repo as a zip file][download] and unzip it, or clone
the repo:
### Run a gRPC application
```sh
$ git clone https://github.com/grpc/grpc-kotlin
```
2. Change to the examples directory:
```sh
$ cd grpc-kotlin/examples
```
### Run the example
From the `examples` directory:
@ -36,29 +40,29 @@ From the `examples` directory:
2. Run the server:
```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:
```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
server for the client to call. Our gRPC service is defined using [Protocol
Buffers][pb]; you can find out lots more about how to define a service in a
`.proto` file in [Basics tutorial](../basics/). For now
all you need to know is that both the server and the client "stub" have a
In this section, you'll update the app with an extra server method. The app's
gRPC service, named `Greeter`, is defined using [protocol buffers][pb]. To learn
more about how to define a service in a `.proto` file, see [Basics tutorial][].
For now, 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
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:
```protobuf
// The greeting service definition.
service Greeter {
@ -76,9 +80,10 @@ message HelloReply {
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()`
method, with the same request and response types:
Open `helloworld/hello_world.proto` from the
[protos/src/main/proto/io/grpc/examples][protos-src] folder, and add a
new `SayHelloAgain()` method, with the same request and response types:
```protobuf
// The greeting service definition.
@ -102,21 +107,21 @@ message HelloReply {
Remember to save the file!
### Update and run the application
### Update the app
When we recompile the example, normal compilation will regenerate
`HelloWorldGrpcKt.kt`, which contains our generated gRPC client and server classes.
This also regenerates classes for populating, serializing, and retrieving our
request and response types.
When you build the example, the build process regenerates `HelloWorldGrpcKt.kt`,
which contains the generated gRPC client and server classes. This also
regenerates classes for populating, serializing, and retrieving our request and
response types.
However, we still need to implement and call the new method in the human-written
parts of our example application.
However, you still need to implement and call the new method in the
hand-written parts of the example app.
#### Update the server
In the same directory, open
`src/main/kotlin/io/grpc/examples/helloworld/HelloWorldServer.kt`. Implement the
new method like this:
Open `helloworld/HelloWorldServer.kt` from the
[server/src/main/kotlin/io/grpc/examples][server-src] folder. Implement the new
method like this:
```kotlin
private class HelloWorldService : GreeterGrpcKt.GreeterCoroutineImplBase() {
@ -134,22 +139,22 @@ private class HelloWorldService : GreeterGrpcKt.GreeterCoroutineImplBase() {
#### Update the client
In the same directory, open
`src/main/kotlin/io/grpc/examples/helloworld/HelloWorldClient.kt`. Call the new
Open `helloworld/HelloWorldClient.kt` from the
[client/src/main/kotlin/io/grpc/examples][client-src] folder. Call the new
method like this:
```kotlin
class HelloWorldClient constructor(
class HelloWorldClient(
private val channel: ManagedChannel
) : Closeable {
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 response = async { stub.sayHello(request) }
println("Received: ${response.await().message}")
val againResponse = async { stub.sayHelloAgain(request) }
println("Received: ${againResponse.await().message}")
val response = stub.sayHello(request)
println("Received: ${response.message}")
val againResponse = stub.sayHelloAgain(request)
println("Received: ${againResponse.message}")
}
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
from the `examples` directory:
@ -172,19 +177,15 @@ from the `examples` directory:
2. Run the server:
```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
command-line argument:
```sh
$ ./build/install/examples/bin/hello-world-client Alice
```
You'll see the following output:
```nocode
$ ./client/build/install/client/bin/hello-world-client Alice
Received: Hello 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/)
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).
[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
[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