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Returning JSON with spring on 404 in XML free project

I am currently setting up a Spring MVC application (version 4.1.4.RELEASE) and I want the application to return a JSON string on a 404 error rather than the default html response. I am using Tomcat 8 as my server. I have what I think should be correct, however it isn't behaving in the manner that I expect. What I'm trying to do is based off of this answer.
public class SpringWebAppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer{
...
#Override
protected void customizeRegistration(ServletRegistration.Dynamic registration){
registration.setInitParameter("throwExceptionIfNoHandlerFound","true");
}
}
and then I have an exception controller (which is different than the question I based my solution off of, however I don't believe that is an issue as I am under the impression that #ControllerAdvice is an acceptable way to manage this based off of the Spring Docs. It looks something like:
#ControllerAdvice
public class GlobalExceptionController{
#ResponseStatus(value=HttpStatus.NOT_FOUND)
#ExceptionHandler(HttpRequestMethodNotSupportedException.class)
public Message handleMethodNotSupported(HttpServletRequest request){
...
}
#ResponseStatus(value=HttpStatus.NOT_FOUND)
#ExceptionHandler(NoSuchRequestHandlingMethodException.class)
public Message handleBadRequest(HttpServletRequest request){
...
}
#ResponseStatus(value=HttpStatus.NOT_FOUND)
#ExceptionHandler(NoHandlerFoundException.class)
public Message requestHandlingNoHandlerFound(HttpServletRequest request){
...
}
...
}
It continues to send back the default response. I know for a fact that it is hitting my customizeRegistration() function because breakpoints stop it, however, any breakpoints that I have in my GlobalException class are not hit. Also, the GlobalException class is within a package that is hit by a #ComponentScan() annotation, so I am fairly confident that it is also being handled by spring.
I assume I'm missing something obvious, any help would be greatly appreciated.

I don't think the return type you're trying to use is supported. Have you tried changing your return value to ResponseEntity or adding a #ResponseBody annotation?
From the docs:
A ModelAndView object (Servlet MVC or Portlet MVC).
A Model object, with the view name implicitly determined through a RequestToViewNameTranslator.
A Map object for exposing a model, with the view name implicitly determined through a RequestToViewNameTranslator.
A View object.
A String value which is interpreted as view name.
#ResponseBody annotated methods (Servlet-only) to set the response content. The return value will be converted to the response stream
using message converters.
An HttpEntity or ResponseEntity object (Servlet-only) to set response headers and content. The ResponseEntity body will be
converted and written to the response stream using message converters.
void if the method handles the response itself (by writing the response content directly, declaring an argument of type
ServletResponse / HttpServletResponse / RenderResponse for that
purpose) or if the view name is supposed to be implicitly determined
through a RequestToViewNameTranslator (not declaring a response
argument in the handler method signature; only applicable in a Servlet
environment).

how handler mapping works in spring mvc

I am new to spring mvc. I am debugging a mvc code as given below
#Controller
#RequestMapping("/register")
public class RegisterController extends BroadleafRegisterController {
#RequestMapping(method=RequestMethod.GET)
public String register(HttpServletRequest request, HttpServletResponse response, Model model,
#ModelAttribute("registrationForm") RegisterCustomerForm registerCustomerForm) {
return super.register(registerCustomerForm, request, response, model);
}
#RequestMapping(method=RequestMethod.POST)
public String processRegister(HttpServletRequest request, HttpServletResponse response, Model model,
#ModelAttribute("registrationForm") RegisterCustomerForm registerCustomerForm, BindingResult errors) throws ServiceException, PricingException {
return super.processRegister(registerCustomerForm, errors, request, response, model);
}
#ModelAttribute("registrationForm")
public RegisterCustomerForm initCustomerRegistrationForm() {
return super.initCustomerRegistrationForm();
}
}
above is a spring handler class. for /register request i was thinking regsister() method should called but before this method inintcustomerRegisterationForm() is called i do not know why and how this method is called. I searched this in google but not find any useful information. I think this is like a interceptor method as in struts2. Please tell us how this method is called
Thanks

The initCustomerRegistrationForm() is being called because it is the 'model' of your controller. The model is typically always need for a get and post request for a specific form and represents the data entered into the form.
If you want your form pre-populated with some data, then you would add that data to the 'model'. The 'model' is also what is submitted to the post request then submitting a form.

According to spring documentation
#ModelAttribute methods are used to populate the model with commonly needed attributes for example to fill a drop-down with states or with pet types, or to retrieve a command object like Account in order to use it to represent the data on an HTML form.
A controller can have any number of #ModelAttribute methods. All such methods are invoked before #RequestMapping methods of the same controller.
Which explains why the initCustomerRegistrationForm() method is called before request mapping methods.

Spring MVC: default view objects

I use ModelAndView objects as all people do:
ModelAndView result = new ModelAndView("view");
result.addObject("requests", requestsService.getListByBackoffice(filter, page, Config.RECORDS_PER_PAGE));
But I noticed that I have a couple of objects that I use always in most of the views.. So the question is - is there any solutions to create some kind of default assigned objects that are passed to view automatically?
Thank you

You can register a HandlerInterceptor with your DispatcherServlet. You then implement the postHandle() method:
public class CustomInterceptor extends HandlerInterceptorAdapter /* which implements HandlerInterceptor */ {
#Override
public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
modelAndView.addObject("myObject", new Object());
// add as many as you wish
}
}
NOTE: The ModelAndView object may be null. This may occur if your handler method was writing to the response body directly, for example with #ResponseBody.
Depending on the url pattern you used when registering the Interceptor, the postHandle() will get called and populate your model with any objects you want.
You can also register a servlet Filter (in web.xml or WebApplicationInitializer). The filter simply adds the request attributes before dispatching to the servlet.
public class CustomFilter implements Filter {
#Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
request.setAttribute("myObject", new Object());
chain.doFilter(request, response);
}
// ... init and destroy methods
}
NOTE: At some point during the request lifecycle, Spring adds all attributes in the model to your request attributes.
The disadvantage here is that you add the attributes whether or not your #Controller worked, as the Filter is called before Spring's DispatcherServlet. Also, the Filter is managed by your servlet container (workarounds exist) and therefore it's difficult to inject Spring beans into it.

first solution:
I have not tried such but can do like creating ModelAndView object in Constructor or somewhere which you call always, set object which you always want to pass as default there only.
call setViewName() in respective methods and add respective objects which you want to set.
second solution:
write one method which is adding that default object and call that method wherever you need (nothing but what interceptor do).

Difference between handleRequestInternal and handleRequest

I have just started spring, I found that somewhere we are using handlerequest() method in controller and somewhere we are using handlerequestinternal() method.
I have tried google-ing this, but did not find any specific point.
Can any one explain what is the difference between these two functions and when we should implement each of them?
As I know spring framework will call by default handlerequest() function, so we can put our service layer there itself.
I am sure handlerequestinternal() must be providing some extra feature, but not sure.
Please help me to understand this.

Both handleRequest and handleRequestInternal are used by the old Spring 2.0 controller framework.
handleRequestInternal is used when you're extending one of the pre-supplied base support classes (e.g. AbstractController, SimpleFormController, etc). These use the Template design pattern, and you supply your business logic in that method.
handleRequest is the method specified on the Controller interface itself. If you directly implement that interface, rather than extending one of the above base classes, then you need to implement handleRequest directly.
Both are obsolete, and not used in controllers written for Spring 2.5 and later.

public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {
this.checkAndPrepare(request, response, this instanceof LastModified);
if (this.synchronizeOnSession) {
HttpSession session = request.getSession(false);
if (session != null) {
Object mutex = WebUtils.getSessionMutex(session);
synchronized(mutex) {
return this.handleRequestInternal(request, response);
}
}
}
return this.handleRequestInternal(request, response);
}
protected abstract ModelAndView handleRequestInternal(HttpServletRequest var1, HttpServletResponse var2) throws Exception;
}
if in controller template classes like AbstractController and ParameterizableViewConterollers in this it will the child classes of Controller interface so spring peoples internally override the handleRequest method and call the abstract handleRequestInternal method so whenever we are using template classes we use this method otherwise we use the handleRequest() method only this the difference i think!.

Spring - Redirect after POST (even with validation errors)

I'm trying to figure out how to "preserve" the BindingResult so it can be used in a subsequent GET via the Spring <form:errors> tag. The reason I want to do this is because of Google App Engine's SSL limitations. I have a form which is displayed via HTTP and the post is to an HTTPS URL. If I only forward rather than redirect then the user would see the https://whatever.appspot.com/my/form URL. I'm trying to avoid this. Any ideas how to approach this?
Below is what I'd like to do, but I only see validation errors when I use return "create".
#RequestMapping(value = "/submit", method = RequestMethod.POST)
public final String submit(
#ModelAttribute("register") #Valid final Register register,
final BindingResult binding) {
if (binding.hasErrors()) {
return "redirect:/register/create";
}
return "redirect:/register/success";
}

Since Spring 3.1 you can use RedirectAttributes. Add the attributes that you want to have available before doing the redirect. Add both, the BindingResult and the object that you are using to validate, in this case Register.
For BindingResult you will use the name: "org.springframework.validation.BindingResult.[name of your ModelAttribute]".
For the object that you are using to validate you will use the name of ModelAttribute.
To use RedirectAttributes you have to add this in your config file. Among other things you are telling to Spring to use some newer classes:
<mvc:annotation-driven />
Now the errors will be displayed wherever you are redirecting
#RequestMapping(value = "/submit", method = RequestMethod.POST)
public final String submit(#ModelAttribute("register") #Valid final Register register, final BindingResult binding, RedirectAttributes attr, HttpSession session) {
if (binding.hasErrors()) {
attr.addFlashAttribute("org.springframework.validation.BindingResult.register", binding);
attr.addFlashAttribute("register", register);
return "redirect:/register/create";
}
return "redirect:/register/success";
}

In addition to Oscar's nice answer, if you are following that RedirectAttributes approach, do not forget that you are actually passing the modelAttribute to the redirected page. This means if you create a new instance of that modelAttribute for the redirected page (in a controller), you will lose the validation errors. So, if your POST controller method is something like this:
#RequestMapping(value = "/submit", method = RequestMethod.POST)
public final String submit(#ModelAttribute("register") #Valid final Register register, final BindingResult binding, RedirectAttributes attr, HttpSession session) {
if (binding.hasErrors()) {
attr.addFlashAttribute("org.springframework.validation.BindingResult.register", binding);
attr.addFlashAttribute("register", register);
return "redirect:/register/create";
}
return "redirect:/register/success";
}
Then you will probably need to do a modification in your register create page GET controller. From this:
#RequestMapping(value = "/register/create", method = RequestMethod.GET)
public String registerCreatePage(Model model) {
// some stuff
model.addAttribute("register", new Register());
// some more stuff
}
to
#RequestMapping(value = "/register/create", method = RequestMethod.GET)
public String registerCreatePage(Model model) {
// some stuff
if (!model.containsAttribute("register")) {
model.addAttribute("register", new Register());
}
// some more stuff
}
Source: http://gerrydevstory.com/2013/07/11/preserving-validation-error-messages-on-spring-mvc-form-post-redirect-get/

I would question why you need the redirect. Why not just submit to the same URL and have it respond differently to a POST? Nevertheless, if you really want to do this:
#RequestMapping(value = "/submit", method = RequestMethod.POST)
public final String submit(
#ModelAttribute("register") #Valid final Register register,
final BindingResult binding,
HttpSession session) {
if (binding.hasErrors()) {
session.setAttribute("register",register);
session.setAttribute("binding",binding);
return "redirect:/register/create";
}
return "redirect:/register/success";
}
Then in your "create" method:
model.put("register",session.getAttribute("register"));
model.put("org.springframework.validation.BindingResult.register",session.getAttribute("register"));

The problem is you're redirecting to a new controller, rather than rendering the view and returning the processed form page. You need to do something along the lines of:
String FORM_VIEW = wherever_your_form_page_resides
...
if (binding.hasErrors())
return FORM_VIEW;
I would keep the paths outside of any methods due to code duplication of strings.

The only way to persist objects between requests (ie a redirect) is to store the object in a session attribute. So you would include "HttpServletRequest request" in method parameters for both methods (ie, get and post) and retrieve the object via request.getAttribute("binding"). That said, and having not tried it myself you may need to figure out how to re-bind the binding to the object in the new request.
Another "un-nicer" way is to just change the browser URL using javascript

I don't know the exact issue with Google App Engine but using the ForwardedHeaderFilter may help to preserve the original scheme that the client used. This filter was added in Spring Framework 4.3 but some Servlet containers provide similar filters and the filter is self-sufficient so you can also just grab the source if needed.

Perhaps this is a bit simplistic, but have you tried adding it to your Model? I.e., include the Model in your method's arguments, then add the BindingResult to it, which is then available in your view.
model.addAttribute("binding",binding);
I think you may have to use a forward rather than a redirect (in my head I can't remember if a redirect loses the session or not — I could be wrong about this as I don't have any documentation handy, i.e., if you're not getting the BindingResult after adding it to the Model, try using a forward instead to confirm this).