def get_association(server_url, handle=nil)
unless handle.nil?
filename = get_association_filename(server_url, handle)
return _get_association(filename)
end
prefix = filename_from_url(server_url)
assoc_filenames = Dir.entries(@association_dir)
assoc_filenames = assoc_filenames.find_all { |f| f.index(prefix) == 0 }
assocs = assoc_filenames.collect do |f|
_get_association(@association_dir.join(f))
end
assocs = assocs.find_all { |a| not a.nil? }
assocs = assocs.sort_by { |a| a.issued }
return nil if assocs.empty?
return assocs[-1]
end