You have a few options 1. Return a java.net.URL from your onSuccess() event - This will only work if your external URL allows GET. You can use the query part of the URL to pass request parameters
2. Use javascript to post a form to the external URL - Redirect after your onSuccess() event to a page which posts a simple non-tapestry form to the external URL. 3. Serverside POST - Use something like apache HttpClient to do the external POST from your server. You might get an external session id back that you can then use in a redirect to the external site. Note, in all of these solutions I have assumed you want to first handle the form in tapestry so you can validate etc.
