JCA to Serveral HOST Connection

Hi, all:
Please help me to clarify following question:
We development a gateway framework(Let we say GWF), our aim is to
connection to different host or framework through plug in "Connection
Adapter". In GWF client(That is out application lie in) can have an
uniform call interface. Here is sample code:
                  private IGateway gw = null;
                   gw = (IGateway)GatewayService.getInstance();
                   EPData input = new EPData("testservice");
                   input.setAttribute("account_number",account_number);
                   input.setAttribute("password",password);
                   EPData result = null;
                   EPRecord er = null;
                   try{
                   result = gw.execute("testservice",input);
                   //er = result.get(1);
                  }catch(GatewayException e){
                   e.printStackTrace();

1, Do we must implement SPI interface? For example implement connection,
transaction and security contracts by our self?
  I haven't experience on write those contract, (we using weblogic6.1)
:-)
2, What is good choice, we development connection adapter or using
existing  connection adapter/ resource Adapter? Where can we find those
adapter, it is free?
3, Our application have to talk with several host: (1)Mainframe(through
Microsoft SNA server), (2),AS/400(TCP/IP),(3)S390(TCP?IP), how to
consider performance?

Any comments or input will be appreciate.
Thanks in advance!

Charles Guo
MSN Messagrer: [email protected]