Neither BindingResult nor plain target object … Exception

Question

Yes, I read it is pretty common problem, but reading those post did not really help me.

The short story is that I wanna submit a form on showAllComments

Answer 1

You need to add a your form bean class ie Comment, as an attribute to your model when you show the showAllComments.jsp in the logincontroller.

@RequestMapping(value = "/log_in", method = RequestMethod.POST)
public ModelAndView tryToLogin(@RequestParam("uName") String uName, @RequestParam("pW") String pW,      HttpServletResponse response, HttpServletRequest request) {
    ModelAndView ret = new ModelAndView("login", "command", new User());
    User user = userService.existingUser(uName, pW);
    loggedInUser = new User();
    model.addAttribute("command", new Comment());
    if (user != null) {
        Map<String, Object> model = new HashMap<String, Object>();
            model.put("COMMENTS", allComments);
            model.put("LOGGED_IN_USER", loggedInUser);
        ret = ModelAndView("showAllComments", model);
    }
    return ret;
}

This should work fine.

UPDATE

And it is not a good practise to use 'command' as the command object name. For the class comment you can use a 'comment' or something like that. If your doing that, Update your form with the following code.

<form:form method="post" action="postNewComment.html" commandName="comment">
    <table>
        <tr>
            <td><form:label path="comment">
                    COMMENT
                </form:label></td>
            <td><form:input path="comment" /></td>
        </tr>
        <tr>
            <td colspan="2"><input type="submit"
                value="WRITE" /></td>
        </tr>
    </table>
</form:form>

Do the same change at all other places, viz

model.addAttribute("comment", new Comment());

and

@ModelAttribute("comment")

UPDATE 2

    @RequestMapping(value="userRegistration", method = RequestMethod.GET)
public ModelAndView showUserRegistrationForm(Model model){
    model.addAttribute("user", new AccountDetailsForm());
    return new ModelAndView("userRegistration");
}