Standard Protocols and Messaing standards for Financial Transaction?

I am trying to build a Payment gateway where other institutions will post transaction messages. I will have to process them. Processing is not a issue. Now what protocols standard should I use for keeping the gateway standard, to have a smooth integrations with other Financial Institutions.

I did a little research and decided to use Webservices with wsdl using JavaCFX. But each transaction will have so many parameters eg. 15. Having a function with so many parameters will be messy. So thought using ISO8583 messaging standard. So the webservice function will loo开发者_JAVA百科k like

String postTransaction(String ISO_String)

The function will receive a serialised ISO 8583 Message as a string and return back a reply ISO 8583 message. Is this standard? Any Suggestions?

As the comment from Chochos says, WSDL should "describe" a webservice. A single ISO_String parameter is a very poor description of what the webservice requires an input. There is no obvious benefit (in fact, there is some overhead of) doing this the webservice way instead of asynchronous communication.