Steve's Blog Technical Information on Oracle Middleware.

With Jdev 11g, after generating a Web Service from a java class, the WSDL contains the following 
parameter names:

...
<xsd:complexType name="sayHello">
  <xsd:sequence>
     <xsd:element name="arg0" type="xsd:string"/>
     <xsd:element name="arg1" type="xsd:string"/>
  </xsd:sequence>
</xsd:complexType>
...

My java code function looks like:
...
public String sayHello(String firstname, String lastname) {
  return "Hello " + firstname + " " + lastname;
}
...

With Jdev 10g , the same code generates the appropriate values:
...
<xsd:complexType name="sayHello">
  <xsd:sequence>
     <xsd:element name="firstname" type="xsd:string"/>
     <xsd:element name="lastname" type="xsd:string"/>
  </xsd:sequence>
</xsd:complexType>
...

To workaround this in 11g, I need to create my java class as follows:

package project1;

import javax.jws.WebMethod;
import javax.jws.WebParam;
import javax.jws.WebService;

@WebService
public class Class1 {
    @WebMethod
    public String sayHello(@WebParam(name = "fname") String firstname,
                           @WebParam(name = "lname") String lastname) {
        return "Hello " + firstname + " " + lastname;
    }
}

And now my generated WSDL looks like:
...
<xsd:complexType name="sayHello">
  <xsd:sequence>
     <xsd:element name="fname" type="xsd:string"/>
     <xsd:element name="lname" type="xsd:string"/>
  </xsd:sequence>
</xsd:complexType>
...

http://java.sun.com/javaee/5/docs/api/javax/jws/WebParam.html