spring security 3.0.3 custom login form

This handy link shows how to make a form th开发者_开发技巧at replaces the built-in spring security login form in 2.5.6. Can anyone illuminate the corresponding question for 3.0.3? Something has changed, the old form does not work.

When I click on submit it comes back to the login page with the error flag, and the username changes from what I type to 'null'.

This suggests that the names of the required form fields have changed from j_username and j_password to something else.

I'm also suspicious of

<input type="text" name="j_username" id="j_username"
    <c:if test="${not empty param.login_error}">value='<%= 
 session.getAttribute(AuthenticationProcessingFilter.SPRING_SECURITY_LAST_USERNAME_KEY) %>'
 </c:if> />

since AuthenticationProcessingFilter is deprecated.

And the answer is: POST is required now. I wish it had produced that error message the first time.