PowerBuilder

Read S3 Object Metadata of File Already Uploaded to S3

See more Amazon S3 Examples

Demonstrates how to retrieve the metadata from an S3 object.

The HEAD operation retrieves metadata from an object without returning the object itself. This operation is useful if you are interested only in an object's metadata. To use HEAD, you must have READ access to the object.

A HEAD request has the same options as a GET operation on an object. The response is identical to the GET response except that there is no response body.

PowerBuilder

integer li_rc
oleobject loo_Http
string ls_BucketName
string ls_ObjectName
integer li_Retval
string ls_ResponseHeader
oleobject loo_Mime
integer i
integer li_NumHeaders
oleobject loo_SbName

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

loo_Http = create oleobject
li_rc = loo_Http.ConnectToNewObject("Chilkat.Http")
if li_rc < 0 then
    destroy loo_Http
    MessageBox("Error","Connecting to COM object failed")
    return
end if

// Insert your AWS keys here:
loo_Http.AwsAccessKey = "AWS_ACCESS_KEY"
loo_Http.AwsSecretKey = "AWS_SECRET_KEY"

ls_BucketName = "chilkat.ocean"
ls_ObjectName = "seahorse.jpg"

// User-defined metadata are name/value pairs, and are returned in the HTTP response header.
// Metadata header names begin with "x-amz-meta-" to distinguish them from other HTTP headers.
// Note that Amazon S3 stores user-defined metadata keys in lowercase.

// A HEAD request can be sent to return the response header without the response body.
// The S3_FileExists method sends a HEAD request.
// It can be used to get the response header.
li_Retval = loo_Http.S3_FileExists(ls_BucketName,ls_ObjectName)
if li_Retval < 0 then
    Write-Debug "Failed to check for the S3 object existence"
    Write-Debug loo_Http.LastErrorText
    destroy loo_Http
    return
end if

if li_Retval = 0 then
    Write-Debug "The S3 object does not exist."
    destroy loo_Http
    return
end if

// The response header is available in the LastResponseHeader property.
ls_ResponseHeader = loo_Http.LastResponseHeader
Write-Debug "Response header:"
Write-Debug ls_ResponseHeader
Write-Debug "--"

// Here is an example response header:

// 	x-amz-id-2: uS4Flff04M8x5YWajU231TP0ClBL19mMhuyfU5ZVQd6NsUHXVhHK+H3b0sjxY98Fujet1ejhyzk=
// 	x-amz-request-id: 27950009AA8E68AA
// 	Date: Mon, 23 Jan 2017 20:12:58 GMT
// 	Last-Modified: Fri, 20 Jan 2017 00:22:57 GMT
// 	ETag: "a8551f0a5437f43a796fca7623ee9232"
// 	x-amz-meta-species: big-belly seahorse
// 	x-amz-meta-genus: Hippocampus
// 	x-amz-meta-habitat: shallow tropical and temperate waters
// 	Accept-Ranges: bytes
// 	Content-Type: image/jpg
// 	Content-Length: 24388
// 	Server: AmazonS3

// HTTP requests and responses are MIME.  For easy parsing, the response header
// can be loaded into a Chilkat MIME object
loo_Mime = create oleobject
li_rc = loo_Mime.ConnectToNewObject("Chilkat.Mime")

loo_Mime.LoadMime(ls_ResponseHeader)

// Examine the metadata values:
Write-Debug "x-amz-meta-species: " + loo_Mime.GetHeaderField("x-amz-meta-species")
Write-Debug "x-amz-meta-genus: " + loo_Mime.GetHeaderField("x-amz-meta-genus")
Write-Debug "x-amz-meta-habitat: " + loo_Mime.GetHeaderField("x-amz-meta-habitat")
Write-Debug "--"

// It is possible to iterate over the header fields to find all x-amz-meta* headers
i = 0
li_NumHeaders = loo_Mime.NumHeaderFields
loo_SbName = create oleobject
li_rc = loo_SbName.ConnectToNewObject("Chilkat.StringBuilder")

do while i < li_NumHeaders
    loo_SbName.SetString(loo_Mime.GetHeaderFieldName(i))
    if loo_SbName.StartsWith("x-amz-meta",0) = 1 then
        Write-Debug loo_SbName.GetAsString() + ": " + loo_Mime.GetHeaderFieldValue(i)
    end if

    i = i + 1
loop

// The output:

// 	x-amz-meta-species: big-belly seahorse
// 	x-amz-meta-genus: Hippocampus
// 	x-amz-meta-habitat: shallow tropical and temperate waters


destroy loo_Http
destroy loo_Mime
destroy loo_SbName