Question

I’m updating existing objects in an Amazon S3 bucket to set some metadata. I’d like to set the HTTP Expires header for each object to better handle HTTP/1.0 clients.

We’re using the AWS Java SDK, which allows for metadata changes to an object without re-uploading the object content. We do this using CopyObjectRequest to copy an object to itself. The ObjectMetadata class allows us to set the Cache-Control, Content-Type and several other headers. But not the Expires header.

I know that S3 stores and serves the Expires header for objects PUT using the REST API. Is there a way to do this from the Java SDK?

Updated to indicate that we are using CopyObjectRequest

Answer 1

To change the metadata of an existing Amazon S3 object, you need to copy the object to itself and provide the desired new metadata on the fly, see copyObject():

By default, all object metadata for the source object are copied to
the new destination object, unless new object metadata in the
specified CopyObjectRequest is provided.

This can be achieved like so approximately (fragment from the top of my head, so beware):

AmazonS3 s3 = new AmazonS3Client();

String bucketName = "bucketName ";
String key = "key.txt";
ObjectMetadata newObjectMetadata = new ObjectMetadata();
// ... whatever you desire, e.g.:
newObjectMetadata.setHeader("Expires", "Thu, 21 Mar 2042 08:16:32 GMT");

CopyObjectRequest copyObjectRequest = new CopyObjectRequest()
                 .WithSourceBucketName(bucketName)
                 .WithSourceKey(key)
                 .WithDestinationBucket(bucketName)
                 .WithDestinationKey(key)
                 .withNewObjectMetadata(newObjectMetadata);

s3.copyObject(copyObjectRequest);

Please be aware of the following easy to miss, but important copyObject() constraint:

The Amazon S3 Acccess Control List (ACL) is not copied to the new
object. The new object will have the default Amazon S3 ACL,
CannedAccessControlList.Private, unless one is explicitly provided in
the specified CopyObjectRequest.

This is not accounted for in my code fragment yet!

Good luck!