Exposing Haskell functions with String arguments in dll

Hi, I want to expose the following Haskell function in dll to call it from Java application: trans: String -> IO String I read that I shoud use tools like GreenCard, HDirect or some marshalling libraries, but not sure, which way is better. If anyone has experience in this, I will be very grateful for an example, which shows the steps of bilding such dll. Thanks in advance, Janna Khegai.