(Excel) Fetch S3 Object Metadata

Demonstrates how to get the metadata for an S3 object using the REST API.

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.

Download Excel Class Modules Chilkat Excel Class Modules

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

Dim rest As Chilkat.Rest
Set rest = Chilkat.NewRest

' Connect to the Amazon AWS REST server using the correct region (in this example, "us-west-2")

bTls = True

port = 443

bAutoReconnect = True

success = rest.Connect("s3-us-west-2.amazonaws.com",port,bTls,bAutoReconnect)

' Provide AWS credentials for the REST call.
Dim authAws As Chilkat.AuthAws
Set authAws = Chilkat.NewAuthAws
authAws.AccessKey = "AWS_ACCESS_KEY"
authAws.SecretKey = "AWS_SECRET_KEY"
authAws.ServiceName = "s3"
' Make sure the Region agrees with the region in the Connect.
authAws.Region = "us-west-2"
success = rest.SetAuthAws(authAws)

' 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.

' Set the bucket name via the HOST header.
' In this case, the bucket name is "chilkat.ocean".
rest.Host = "chilkat.ocean.s3.amazonaws.com"

' Send the HEAD request.
success = rest.SendReqNoBody("HEAD","/seahorse.jpg")
If (success <> True) Then
    Debug.Print rest.LastErrorText
    Exit Sub
End If

' Read the response header.

responseStatusCode = rest.ReadResponseHeader()
If (responseStatusCode < 0) Then
    Debug.Print rest.LastErrorText
    Exit Sub
End If

Debug.Print "Response status code = "; responseStatusCode
If (responseStatusCode <> 200) Then
    Debug.Print rest.ResponseHeader
    Debug.Print "Object does not exist."
    Exit Sub
End If

' Show the full response header that was received:
Debug.Print "Response header:"
Debug.Print rest.ResponseHeader
Debug.Print "--"

' 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

' Examine particular response headers (the object metadata headers..)
Debug.Print "x-amz-meta-species: "; rest.ResponseHdrByName("x-amz-meta-species")
Debug.Print "x-amz-meta-genus: "; rest.ResponseHdrByName("x-amz-meta-genus")
Debug.Print "x-amz-meta-habitat: "; rest.ResponseHdrByName("x-amz-meta-habitat")
Debug.Print "--"

' It is possible to iterate over the header fields to find all x-amz-meta* headers

i = 0

numHeaders = rest.NumResponseHeaders
Dim sbName As Chilkat.StringBuilder
Set sbName = Chilkat.NewStringBuilder
Do While i < numHeaders
    Dim success As Boolean
    success = sbName.SetString(rest.ResponseHdrName(i))
    If (sbName.StartsWith("x-amz-meta",False) = True) Then
        Debug.Print sbName.GetAsString(); ": "; rest.ResponseHdrValue(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