Uploading Blobs and Clobs

The fileAccept() element applies only to Blob or Clob parameters, indicating the type of file to accept when uploading a new value.

For example:

public class Scanner {

    public ScannedDocument newScan(
                @Parameter(
                    fileAccept="image/*"        (1)
                )
                final Blob scannedImage) {
        // ...
    }
}
1 as per reference docs, either a media type (such as image/*) or a file type extension (such as .png).