I need to generate enterprise WSDL file in salesForce, but I don't see this option in
Setup -> Develop -> API.
I just see a page telling me for more information visit http://developer.salesforce.com.
I'm using 30 day trial, would that be the problem?
Try right clicking the page and click "View page source". The Source IS the XML document
The FuseIT Wsdl2Apex tool can generate HttpRequests using the DOM classes. To do this you need to select the HTTP Request option for the required methods.
Here is an example of how the generated HTTPRequest version of the login method appears.
Each request and response element gets a constructor that works with a Dom.XmlNode and a corresponding method to populate a Dom.XmlNode. I found you could use straight string processing for reasonably simple requests and responses. With more complex parameters and responses it was easier to have an object that could serialize and deserialize the XML.
That said, it can generate WebServiceCallout.invoke compatible classes for the entire Partner API. Is there a particular web method that is causing you issues?
Once you have the WSDL2Apex generated classes working you can capture the CALLOUT_REQUEST and CALLOUT_RESPONSE log messages if you want the strings.
If you are feeling inspired there is also the open source version of WSDL2Apex. You could generate the string version of the requests directly from there.
I'll second @AAU's comment about SoapUI. You add the WSDL in and it will generate the required Request stub for you to fill in the parameters.
Best Answer
Trial version accounts do not provide WSDL. You need to have developer or enterprise account to generate WSDL for your environment.
If you are not able to see it in the options then it might be because you may not be logged in as admin or with Modify All Data permission and that might be stopping you from generating the WSDL. Else the procedure is quite direct Setup->Develop->API->Select the type of WSDL you wish to generate. Attaching an snapshot for the same