Ktor HTTP客户端-请求进度 [英] Ktor http client - request progress

问题描述

如何在Ktor http客户端中监视请求进度?

How do I monitor request progress in Ktor http client?

例如:我有这样的要求:

For example: I have request like this:

val response = HttpClient().get<String>("https://stackoverflow.com/")

并且我想用进度条监视请求进度:

and I want to monitor request progress with progress bar like this:

fun progress(downloaded: Long, contentLength: Long) {
    // Update progress bar or whatever
}

如何设置progress()由HttpClient调用?

How do I set progress() to be called by HttpClient?

edit:这是Kotlin Multiplatform项目.相关的依赖项是:

edit: This is Kotlin Multiplatform project. Relevant dependencies are:

implementation 'io.ktor:ktor-client-core:1.2.5'
implementation 'io.ktor:ktor-client-cio:1.2.5'

推荐答案

在 Ktor <1.3.2 中，您可以通过请求ByteReadChannel而不是String来监视下载进度.

In Ktor<1.3.2, you can monitor your download progress by requesting a ByteReadChannel instead of a String.

缺点是，这样一来，您将无法获得文件的内容大小，但是可以通过单独的HEAD请求轻松获得(如果下载的文件足够大，则不会增加太多开销)需要进度监控)

The downside is, that this way you won't get the content size of your file, but it can be easily obtained with a separate HEAD request (which should not add too much overhead if you are downloading file that is large enough to require progress monitoring)

val contentLength = // need to get via HEAD reqeuest 

suspend fun download() {
   val url = "https://stackoverflow.com/"
   val client = HttpClient()
   val channel = client.get<ByteReadChannel>(url)
   var total = 0
   var readBytes:Int
  
   var buffer = ByteArray(contentLength)
   do {
      readBytes = channel.readAvailable(buffer, total, 4096 )
      total+=readBytes
      progress(total, contentLength)
   } while (readBytes>0)
   val response = String(buffer)
}

对于 Ktor> 1.3.2 ，采用推荐的方式监视请求进度是使用 HttpStatement ，例如:

For Ktor>1.3.2 the recommended way of monitoring the request progress is to use HttpStatement, e.g.:

suspend fun download() {
  val client = HttpClient()
  val builder = HttpRequestBuilder().apply {
    url("https://stackoverflow.com")
  }
  val httpStatement = HttpStatement(builder,  client)
  httpStatement.execute { response: HttpResponse ->
    // Response is not downloaded here
    val channel = response.receive<ByteReadChannel>()
    val contentLength = response.contentLength()
    requireNotNull(contentLength) {"Header needs to be set by server"}

    var total = 0
    var readBytes:Int
    var buffer = ByteArray(contentLength)  
    do {
      readBytes = channel.readAvailable(buffer, total, 4096 )
      total+=readBytes
      progress(total, contentLength)
    } while (readBytes>0)
      
    val response = String(buffer) 
  }
}

当然，如果下载大文件，使用较小的缓冲区会更明智，然后直接将其写入某个文件，例如:

Of course, if downloading a large file it would be more sensible use a smaller buffer, and directly write it to some file, e.g.:

...
var buffer = ByteArray(4096) 
do {
   readBytes = channel.readAvailable(buffer, 0, 4096 )
   total+=readBytes
   writeToFile(buffer, readBytes) // do something sensible with the read bytes
   progress(total, response.contentLength())
} while (readBytes>0)
...

这篇关于Ktor HTTP客户端-请求进度的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！