DataFlex

REST Asynchronous Streaming Upload Simplified

See more REST Examples

This is example is simplified in that it calls FullRequestStreamAsync instead of making calls to SendReqStreamBodyAsync, ReadResponseHeader, and ReadRespBodyStr.

It demonstrates how to create and write to a stream that feeds an asynchronous upload to cloud storage. This particular example demonstrates an upload to the Azure Cloud Storage service. The same concepts apply to S3, Google Cloud, and Google Drive.

DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoRest
    Boolean iBTls
    Integer iPort
    Boolean iBAutoReconnect
    Variant vAzAuth
    Handle hoAzAuth
    Variant vSendStream
    Handle hoSendStream
    Variant vUploadTask
    Handle hoUploadTask
    Integer i
    Integer iResponseStatusCode
    String sResponseBodyStr
    String sTemp1
    Integer iTemp1
    Boolean bTemp1

    Move False To iSuccess

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    Get Create (RefClass(cComChilkatRest)) To hoRest
    If (Not(IsComObjectCreated(hoRest))) Begin
        Send CreateComObject of hoRest
    End

    // Connect to the Azure Storage Blob Service
    Move True To iBTls
    Move 443 To iPort
    Move True To iBAutoReconnect
    // In this example, the storage account name is "chilkat".
    Get ComConnect Of hoRest "chilkat.blob.core.windows.net" iPort iBTls iBAutoReconnect To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoRest To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Provide Azure Cloud credentials for the REST call.
    Get Create (RefClass(cComChilkatAuthAzureStorage)) To hoAzAuth
    If (Not(IsComObjectCreated(hoAzAuth))) Begin
        Send CreateComObject of hoAzAuth
    End
    Set ComAccessKey Of hoAzAuth To "AZURE_ACCESS_KEY"
    // The account name used here should match the 1st part of the domain passed in the call to Connect (above).
    Set ComAccount Of hoAzAuth To "chilkat"
    Set ComScheme Of hoAzAuth To "SharedKey"
    Set ComService Of hoAzAuth To "Blob"
    // This causes the "x-ms-version: 2021-08-06" header to be automatically added.
    Set ComXMsVersion Of hoAzAuth To "2021-08-06"
    Get pvComObject of hoAzAuth to vAzAuth
    Get ComSetAuthAzureStorage Of hoRest vAzAuth To iSuccess

    // Set some request headers.
    Get ComAddHeader Of hoRest "x-ms-blob-content-disposition" 'attachment; filename="thisIsATest.txt"' To iSuccess
    Get ComAddHeader Of hoRest "x-ms-blob-type" "BlockBlob" To iSuccess
    Get ComAddHeader Of hoRest "x-ms-meta-m1" "v1" To iSuccess
    Get ComAddHeader Of hoRest "x-ms-meta-m2" "v2" To iSuccess

    // Note: The application does not need to explicitly set the following
    // headers: x-ms-date, Authorization, and Content-Length.  These headers
    // are automatically set by Chilkat.

    Get Create (RefClass(cComChilkatStream)) To hoSendStream
    If (Not(IsComObjectCreated(hoSendStream))) Begin
        Send CreateComObject of hoSendStream
    End

    // Create a background thread task to upload from the stream
    // The name of the Azure storage container is "test".
    // After the background task is started and running in a background thread,
    // the foreground thread will write 100 text lines of "this is a test\r\n" to the
    // stream.
    Get pvComObject of hoSendStream to vSendStream
    Get ComFullRequestStreamAsync Of hoRest "PUT" "/test/thisIsATest.txt" vSendStream To vUploadTask
    If (IsComObject(vUploadTask)) Begin
        Get Create (RefClass(cComChilkatTask)) To hoUploadTask
        Set pvComObject Of hoUploadTask To vUploadTask
    End

    // Start the task. 
    Get ComRun Of hoUploadTask To iSuccess

    // The application can write to the stream, and close the stream
    // when finished.  Whatever is written to the stream uploaded to the remote file.

    For i From 1 To 100
        Get ComWriteString Of hoSendStream "This is a test" + (character(13)) + (character(10)) To iSuccess
        If (iSuccess <> True) Begin
            Get ComCancel Of hoUploadTask To iSuccess
            Send Destroy of hoUploadTask
            Showln "Failed to write to sendStream."
            Procedure_Return
        End

    Loop

    // Close the stream to indicate no more data will be sent.
    Get ComWriteClose Of hoSendStream To iSuccess

    // Make sure the uploadTask has finished.
    // It is likely that task is already finished..
    // Wait a max of 5 seconds..
    Get ComWait Of hoUploadTask 5000 To iSuccess

    // FullRequestStreamAsync both sent the request and received the response.
    // Check to see if the task finished properly.
    Get ComStatusInt Of hoUploadTask To iTemp1
    If (iTemp1 <> 7) Begin
        Showln "Task did not end in the finished state."
        Get ComStatus Of hoUploadTask To sTemp1
        Showln "Task status: " sTemp1
        Send Destroy of hoUploadTask
        Procedure_Return
    End

    // Check to see if the call to FullRequestStream in the background thread pool succeeded.
    Get ComTaskSuccess Of hoUploadTask To bTemp1
    If (bTemp1 <> True) Begin
        // Show what would've been the LastErrorText had FullRequestStream been called synchronously
        Get ComResultErrorText Of hoUploadTask To sTemp1
        Showln sTemp1
        Send Destroy of hoUploadTask
        Procedure_Return
    End

    Get ComResponseStatusCode Of hoRest To iResponseStatusCode

    // When successful, the Azure Storage service will respond with a 201 response code,
    // with an empty body.  Therefore, in the success condition, the responseStr is empty.
    If (iResponseStatusCode = 201) Begin
        Showln "File uploaded."
    End
    Else Begin
        // It failed, so examine the response body, if one was returned:
        // Given that FullRequestStream returns a string, the return value is obtained via GetResultString.
        Get ComGetResultString Of hoUploadTask To sResponseBodyStr
        Showln "response body (if any): " sResponseBodyStr

        // Examine the request/response to see what happened.
        Get ComResponseStatusCode Of hoRest To iTemp1
        Showln "response status code = " iTemp1
        Get ComResponseStatusText Of hoRest To sTemp1
        Showln "response status text = " sTemp1
        Get ComResponseHeader Of hoRest To sTemp1
        Showln "response header: " sTemp1
        Showln "---"
        Get ComLastRequestStartLine Of hoRest To sTemp1
        Showln "LastRequestStartLine: " sTemp1
        Get ComLastRequestHeader Of hoRest To sTemp1
        Showln "LastRequestHeader: " sTemp1
    End



End_Procedure