class TransactionResource {

    @GET
    @Path("/transaction/{key}/isSender")
    public Response isSender(@ApiParam("Encoded hash") @PathParam("key") final String ptmHash) {

        LOGGER.debug("Received isSender API request for key {}", ptmHash);

        MessageHash transactionHash = Optional.of(ptmHash)
            .map(Base64.getDecoder()::decode)
            .map(MessageHash::new).get();

        boolean isSender = transactionManager.isSender(transactionHash);

        return Response.ok(isSender).build();
    }

    public  TransactionResource(TransactionManager transactionManager);

}