Reactive way to read and parse file from resources using WebFlux? - json

Question

I wonder what is the correct way to read, parse and serve a file from resources.
Currently, I do something like this:
fun getFile(request: ServerRequest): Mono<ServerResponse> {
val parsedJson =
objectMapper.readValue(readFile("fileName.json"), JsonModel::class.java)
// modify parsed json
return ok().contentType(APPLICATION_JSON).bodyValue(parsedJson)
}
private fun readFile(fileName: String) =
DefaultResourceLoader()
.getResource(fileName)
.inputStream.bufferedReader().use { it.readText() }
I've noticed JsonObjectDecoder class in Netty, but I don't know if can be applied to my use case.
What is the reactive way to do read/parse resource file then?

Answer 1

After expanding #vins answer, I've came to following solution:
Jackson2JsonDecoder()
.decodeToMono(
DataBufferUtils.read(
DefaultResourceLoader()
.getResource("$fileName.json"),
DefaultDataBufferFactory(),
4096
),
ResolvableType.forClass(JsonModel::class.java), null, null
)
.map { it as JsonModel }

Answer 2

You can take a look at Flux.using here for file read.
As you are using Spring framework, You can also take a look at the DataBufferUtils.
This DataBufferUtils uses AsynchronousFileChannel to read the file and it also internally uses Flux.using to release the file once the file is read / cancelled by the subscriber.
#Value("classpath:somefile.json")
private Resource resource;
#GetMapping("/resource")
public Flux<DataBuffer> serve(){
return DataBufferUtils.read(
this.resource,
new DefaultDataBufferFactory(),
4096
);
}