Amazon S3 TransferManager – Batched File Uploads

In addition to all the cool features in TransferManager around asynchronous upload and download management, there are some other great features around batched uploads and downloads of multiple files.

The uploadDirectory and uploadFileList methods in TransferManager make it easy to upload a complete directory, or a list of specific files to Amazon S3, as one background, asynchronous task.

In some cases though, you might want more control over how that data is uploaded, particularly around additional metadata you want to provide for the data you’re uploading. A second form of uploadFileList allows you to pass in an implementation of an ObjectMetadataProvider interface that will let you do just that. For each of the files being uploaded, this ObjectMetadataProvider will receive a callback via the provideObjectMetadata method, allowing it to fill in any additional metadata you’d like to store alongside your object data in Amazon S3.

The following code demonstrates how easy it is to use the ObjectMetadataProvider interface to pass along additional metadata to your uploaded files.

TransferManager tm = new TransferManager(myCredentials);

ObjectMetadataProvider metadataProvider = new ObjectMetadataProvider() {
    void provideObjectMetadata(File file, ObjectMetadata metadata) {
        // If this file is a JPEG, then parse some additional info
        // from the EXIF metadata to store in the object metadata
        if (isJPEG(file)) {
            metadata.addUserMetadata("original-image-date", 
                                     parseExifImageDate(file));
        }
    }
}

MultipleFileUpload upload = tm.uploadFileList(
        myBucket, myKeyPrefix, rootDirectory, fileList, metadataProvider);