http://static.springsource.org/spring-ws/sites/1.5/reference/html/tutorial.html
http://stackoverflow.com/questions/1575268/soap-and-spring
Here are some references above, hopefully they explain things a little bit.
If you want my opinion on the matter here it is
If you generating a service contract(a web service- either
soap or restful then you need a wsdl. It is required...
The purpose of this is use xml to parse your data model classes.
you can use contract first basically you do this by hand(wsdl)
or you can have this generated by using a wizard
The downside of this approach their is no chance of updating.
In my opinion I would always use the first approach...I hope this helps