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https://github.com/google/grpc-kapt
Annotation driven gRPC clients & servers in Kotlin
https://github.com/google/grpc-kapt
grpc kapt kotlin kotlin-coroutines
Last synced: 3 months ago
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Annotation driven gRPC clients & servers in Kotlin
- Host: GitHub
- URL: https://github.com/google/grpc-kapt
- Owner: google
- License: apache-2.0
- Archived: true
- Created: 2019-08-08T22:41:07.000Z (almost 5 years ago)
- Default Branch: master
- Last Pushed: 2019-08-09T05:06:40.000Z (almost 5 years ago)
- Last Synced: 2024-01-26T07:02:24.099Z (5 months ago)
- Topics: grpc, kapt, kotlin, kotlin-coroutines
- Language: Kotlin
- Homepage:
- Size: 147 KB
- Stars: 27
- Watchers: 5
- Forks: 8
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
Lists
- awesome-grpc - grpc-kapt - Annotation driven gRPC clients & servers in Kotlin with coroutines (Language-Specific / Kotlin)
README
# gRPC-kapt
[](https://circleci.com/gh/google/grpc-kapt)
A Kotlin [kapt](https://kotlinlang.org/docs/reference/kapt.html) annotation processor for using
[gRPC](https://grpc.io/) with the transport of your choice (json, proto, etc.).
Supports client & server creation with [coroutines](https://kotlinlang.org/docs/reference/coroutines-overview.html).
*Note* This project is a preview. Please try it out and let us know what you think, but there
are currently no guarantees of any form of stability or support.
## Getting started
To create a gRPC client simply create an interface annotated with `@GrpcClient`.
To implement a server, create another class that inherits from your `@GrpcClient`,
annotate it with `@GrpcServer`, and implement the server-side logic for the methods
that you have defined on the client.
```kotlin
fun main() = runBlocking {
// create the server (use .asGrpcService() to create long running servers)
SimpleServer().asGrpcServer(8080) {
// create a client and query the server
SimpleServiceClient.forAddress("localhost", 8080, channelOptions = { usePlaintext() }).use { client ->
val answer = client.ask(Question("what's this?"))
println(answer)
}
}
}
// define the data types
data class Question(val query: String)
data class Answer(val result: String)
// generate a gRPC client
@GrpcClient
interface SimpleService {
suspend fun ask(question: Question): Answer
}
// generate a gRPC service
@GrpcServer
class SimpleServer : SimpleService {
override suspend fun ask(question: Question) = Answer(result = "you said: '${question.query}'")
}
```
In most cases, you should also add at least one object in your application with the `@GrpcMarshaller`
annotation to specify how the data will be marshaled.
Here's another example using JSON and a bidirectional streaming API:
```kotlin
fun main() = runBlocking {
// create the server
ComplexServer().asGrpcServer(8080) {
// create a client and call the server
ComplexServiceClient.forAddress("localhost", 8080, channelOptions = { usePlaintext() }).use { client ->
// bidirectional streaming
val answers = client.debate(produce {
repeat(10) { i -> send(Question("Question #${i + 1}")) }
})
for (answer in answers) {
println(answer)
}
}
}
}
// generate a gRPC client
@GrpcClient
interface ComplexService {
suspend fun debate(questions: ReceiveChannel): ReceiveChannel
}
// generate & implement a gRPC service
@GrpcServer
class ComplexServer : ComplexService {
override suspend fun debate(questions: ReceiveChannel) = CoroutineScope(coroutineContext).produce {
for (question in questions) {
send(Answer("${question.query}? Sorry, I don't know..."))
}
}
}
// Use JSON serialization for the client & server
@GrpcMarshaller
object MyMarshallerProvider {
private val mapper: ObjectMapper = ObjectMapper().registerModule(KotlinModule())
fun of(type: Class): MethodDescriptor.Marshaller {
return object : MethodDescriptor.Marshaller {
override fun stream(value: T): InputStream = ByteArrayInputStream(mapper.writeValueAsBytes(value))
override fun parse(stream: InputStream): T = stream.bufferedReader().use { mapper.readValue(it, type) }
}
}
}
```
### More Examples
See the [complete example here](example-with-json), a [proto example here](example-with-proto), and a
[Google Cloud API example here](example-with-google-api).
For the adventurous, see the [gRPC reflection](https://github.com/grpc/grpc-java/blob/master/documentation/server-reflection-tutorial.md)
example [here](example-with-proto/src/main/kotlin/com/google/api/example/ExampleReflection.kt).
You can run the examples by running the following in the root of the project:
```bash
$ ./gradlew :runExample
$ ./gradlew :runExampleWithJson
$ ./gradlew :runExampleWithProto
$ ./gradlew :runExampleWithGoogle
$ ./gradlew :runExampleWithProtoReflection
```
*Note*: `:runExampleWithGoogle` requires a [GCP](https://cloud.google.com) project with the
[Langauge API](https://cloud.google.com/natural-language/) enabled. Set the `GOOGLE_APPLICATION_CREDENTIALS`
environment variable before running, i.e.:
```bash
GOOGLE_APPLICATION_CREDENTIALS= ./gradlew :runExampleWithGoogle
```
## Related Projects
It's sort of a simpler version of [kgen](https://github.com/googleapis/gapic-generator-kotlin).
## Contributing
Contributions to this library are always welcome and highly encouraged.
See the [CONTRIBUTING](CONTRIBUTING.md) documentation for more information on how to get started.
## Versioning
This library is currently a *preview* with no guarantees of stability or support. Please get involved and let us know
if you find it useful and we'll work towards a stable version.
## Disclaimer
This is not an official Google product.