(DataFlex) S3 Get Object Metadata, such as ETag

Demonstrates how to get an S3 object's metadata using a HEAD request.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

Use ChilkatAx-win32.pkg

Procedure Test
    Handle hoRest
    Boolean iBTls
    Integer iPort
    Boolean iBAutoReconnect
    Boolean iSuccess
    Variant vAuthAws
    Handle hoAuthAws
    Integer iStatusCode
    String sEtag
    String sTemp1

    // 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 Amazon AWS REST server in the desired region.
    // In this case we connect to S3 in the "us-west-2" region.
    Move True To iBTls
    Move 443 To iPort
    Move True To iBAutoReconnect
    Get ComConnect Of hoRest "s3-us-west-2.amazonaws.com" iPort iBTls iBAutoReconnect To iSuccess

    // Provide AWS credentials.
    Get Create (RefClass(cComChilkatAuthAws)) To hoAuthAws
    If (Not(IsComObjectCreated(hoAuthAws))) Begin
        Send CreateComObject of hoAuthAws
    End
    Set ComAccessKey Of hoAuthAws To "AWS_ACCESS_KEY"
    Set ComSecretKey Of hoAuthAws To "AWS_SECRET_KEY"
    Set ComServiceName Of hoAuthAws To "s3"

    // This particular bucket is in the Oregon region, as opposed to the US Standard,
    // therefore the Region must be set appropriately.
    // Also note that we connected to "s3-us-west-2.amazonaws.com".
    Set ComRegion Of hoAuthAws To "us-west-2"

    Get pvComObject of hoAuthAws to vAuthAws
    Get ComSetAuthAws Of hoRest vAuthAws To iSuccess

    // Note: The above REST connection and setup of the AWS credentials
    // can be done once.  After connecting, any number of REST calls can be made.
    // The "auto reconnect" property passed to rest.Connect indicates that if
    // the connection is lost, a REST method call will automatically reconnect
    // if needed.
    // --------------------------------------------------------------------------

    // Set the bucket name via the HOST header.
    // In this case, the bucket name is "chilkat.ocean".
    // Note that the Host header should use "bucketName.s3.amazonaws.com", not "bucketName.s3-us-west-2.amazonaws.com"
    Set ComHost Of hoRest To "chilkat.ocean.s3.amazonaws.com"

    // Our object is "starfish.jpg".
    // Get the metadata.
    // Since we are sending a HEAD request, we shouldn't use any of the Full* methods.
    // Instead, send the request, then just read the response header.
    Get ComSendReqNoBody Of hoRest "HEAD" "/starfish.jpg" To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoRest To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Now get the response header.
    Get ComReadResponseHeader Of hoRest To iStatusCode
    If (iStatusCode < 0) Begin
        Get ComLastErrorText Of hoRest To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // When successful, the S3 Storage service will respond with a 200 response code,
    // with an XML body.  
    If (iStatusCode <> 200) Begin
        // Examine the request/response to see what happened.
        Showln "response status code = " iStatusCode
        Get ComResponseStatusText Of hoRest To sTemp1
        Showln "response status text = " sTemp1
        Get ComResponseHeader Of hoRest To sTemp1
        Showln "response header: " sTemp1
        Procedure_Return
    End

    // The response header contains information about the S3 object.
    // For example:

    // 	HTTP/1.1 200 OK
    // 	x-amz-id-2: GrV/hrB2EUkBlWc0h3JDdmVIrYDXfPC7CGvo/qSVRmYRPwilAOry8+4r2YWl4xJfa1HRYXrP808=
    // 	x-amz-request-id: 4BDC6D6AEA0BDEF3
    // 	Date: Mon, 13 May 2019 22:03:13 GMT
    // 	Last-Modified: Mon, 10 Nov 2014 16:10:23 GMT
    // 	ETag: "2e9c59dbf2662367dc97dfdda85da048"
    // 	Accept-Ranges: bytes
    // 	Content-Type: image/jpg
    // 	Content-Length: 6229
    // 	Server: AmazonS3

    // Get the ETag response header value:
    Get ComResponseHdrByName Of hoRest "ETag" To sEtag
    Showln "ETag: " sEtag


End_Procedure