Can I use the Ktor client to receive a file with a simple `get`?

# ktor

[dave08]

Can I use the Ktor client to receive a file with a simple get?

[Deactivated User]

Do you mean to get a ByteArray from an url with a single method invocation?

[dave08]

Nope, to get it to download the file to a temporary folder and give me a File object...

[Deactivated User]

I see, I believe there is no built-in functionality for that, but I guess an extension method would do

[dave08]

For uploads TO the server I have:

suspend fun ApplicationCall.receiveFile(uploadDir: String): File =
		receiveMultipart().readPart().let {
			if (it is PartData.FileItem) {
				val ext = File(it.originalFileName).extension
				val uploadName = "upload-${System.currentTimeMillis()}-${it.originalFileName!!.hashCode()}.$ext"

				File(uploadDir, uploadName).also { file ->
					withContext(CommonPool) {
						it.streamProvider().use { its -> file.outputStream().buffered().use { its.copyToSuspend(it) } }
					}
				}
			} else error("Error retreiving upload")
		}

[dave08]

But I need an option to provide an url to "upload" from, meaning I'd download from there...

[Deactivated User]

1 sec, I’m trying to do an extension method for that and I will paste it/put in the samples

[Deactivated User]

Untested (but could be something like this):

suspend fun HttpClient.getAsTempFile(url: String, callback: suspend (file: File) -> Unit) {
	val file = getAsTempFile(url)
	try {
		callback(file)
	} finally {
		file.delete()
	}
}
suspend fun HttpClient.getAsTempFile(url: String): File {
	val file = File.createTempFile("ktor", "http-client").apply { deleteOnExit() }
	val call = call {
		url(URL(url))
		method = HttpMethod.Get
	}
	call.response.content.copyAndClose(file.writeChannel())
	return file
}

[Deactivated User]

ideally you would use the vesion with the callback to handle the lifecycle of the File so it gets deleted asap

[dave08]

Thanks alot! I'll give it a try simple smile

[dave08]

copyAndClose reads everything to memory before it writes to disk?

[e5l]

It use ByteChannel as buffer

[dave08]

Funny, it seems to give me a file of 0 bytes... @Deactivated User

[dave08]

Say from this url <https://www.apkmirror.com/wp-content/themes/APKMirror/download.php?id=452787>

[Deactivated User]

Ok, didn’t tested, so it is possible. Let me try

[Deactivated User]

The problem is that it returns a Found with a Location I guess

[Deactivated User]

you should configure the client to follow redirects

[Deactivated User]

https://ktor.io/clients/http-client.html#apache

[e5l]

or you could use HttpRedirect feature from ktor

[Deactivated User]

fun main(args: Array<String>) {
    runBlocking {
        val client = HttpClient(Apache.config {
            followRedirects = true
        })
        val file = client.getAsTempFile("<https://www.apkmirror.com/wp-content/themes/APKMirror/download.php?id=452787>")
        println(file.readBytes().size)
    }
}

suspend fun HttpClient.getAsTempFile(url: String, callback: suspend (file: File) -> Unit) {
    val file = getAsTempFile(url)
    try {
        callback(file)
    } finally {
        file.delete()
    }
}

suspend fun HttpClient.getAsTempFile(url: String): File {
    val file = File.createTempFile("ktor", "http-client").apply { deleteOnExit() }
    val call = call {
        url(URL(url))
        method = HttpMethod.Get
    }
    println(call.response.status)
    call.response.content.copyAndClose(file.writeChannel())
    return file
}

[Deactivated User]

this works for me

[Deactivated User]

@e5l is there a HttpRedirect feature for the client?

[dave08]

Right, I didn't see it in the docs...

[Deactivated User]

not documented

[Deactivated User]

the followRedirects is in the documentation, and I propose to make it the default, but the HttpRedirect is not documented

[dave08]

But then if it's default, people switching to other clients won't realize they must install HttpRedirect feature to get the same behavior...

[dave08]

It does make sense to have such a default, but it might be inconsistent...

[dave08]

Btw, thanks! Now it works perfectly.

[Deactivated User]

BTW. Adjusted it to check for errors and to use the HttpRedirect:

fun main(args: Array<String>) {
    runBlocking {
        val client = HttpClient(Apache) {
            install(HttpRedirect) {
                maxJumps = 20
            }
        }
        val file = client.getAsTempFile("<https://www.apkmirror.com/wp-content/themes/APKMirror/download.php?id=452787>")
        println(file.readBytes().size)
    }
}

data class HttpClientException(val response: HttpResponse) : IOException("HTTP Error ${response.status}")

suspend fun HttpClient.getAsTempFile(url: String, callback: suspend (file: File) -> Unit) {
    val file = getAsTempFile(url)
    try {
        callback(file)
    } finally {
        file.delete()
    }
}

suspend fun HttpClient.getAsTempFile(url: String): File {
    val file = File.createTempFile("ktor", "http-client").apply { deleteOnExit() }
    val call = call {
        url(URL(url))
        method = HttpMethod.Get
    }
    if (!call.response.status.isSuccess()) {
        throw HttpClientException(call.response)
    }
    call.response.content.copyAndClose(file.writeChannel())
    return file
}

[dave08]

This would be a great addition to the lib 👌🏼

[Deactivated User]

FYI:
- https://github.com/ktorio/ktorio.github.io/commit/9944d7059d496d5e68297bbf1b7cbb87b3e9d6d4
- https://github.com/ktorio/ktor-samples/commit/7c25f23a919b43ce8f1cf6d4f27aa76342576afc