Spring MVC: NullReferenceException when generating form - forms

Question

I'm having problems to figure out this problem. The exception is thrown when I try to go to /users/add url which should show the empty form for creating user entry. After that this exception is propagated throught the whole application.
Here is the controller code:
#Controller
#SessionAttributes(value = "user")
#RequestMapping(value = "/users")
public class UserController {
#Inject
private UserService userService;
#RequestMapping(value = "/", method = RequestMethod.GET)
public ModelAndView getAllUsers() {
List<User> users = userService.getAllUsers();
return new ModelAndView("allUsers", "users", users);
}
#RequestMapping(value = "/add", method = RequestMethod.GET)
public ModelAndView addUser(ModelMap map, #RequestParam(value = "id", required = false) Long id) throws EntityNotFoundException {
User user = null;
if(id != null) {
user = userService.findById(id);
if(user == null)
throw new EntityNotFoundException("Can't find user!");
}
else {
user = new User();
user.setGender(Gender.MALE);
}
map.addAttribute("genders", generateGenders());
return new ModelAndView("addUser", "user", user);
}
#RequestMapping(value = "/add", method = RequestMethod.POST)
public ModelAndView addUser(ModelMap map, #Valid #ModelAttribute(value = "user") User user, BindingResult result,
HttpServletResponse response, final RedirectAttributes redirectAttributes) throws IOException {
if(!result.hasErrors()) {
try {
String userStatus = user.getId() != null ? "User Updated: " : "User Created: ";
userService.saveOrUpdateUser(user);
redirectAttributes.addFlashAttribute("userStatusMessage", userStatus + user.toString());
return new ModelAndView(new RedirectView("/users"));
} catch (EntityNotFoundException e) {
response.sendError(HttpServletResponse.SC_NOT_FOUND, e.getMessage());
return null;
}
}
else {
for (ObjectError error : result.getAllErrors()) {
System.out.println(error.getObjectName() + ": " + error.getDefaultMessage());
}
}
map.addAttribute("genders", generateGenders());
return new ModelAndView("addUser", "user", user);
}
#RequestMapping(value = "/delete", method = RequestMethod.GET)
public ModelAndView deleteUser(#RequestParam(value = "id", required = true) Long id,
HttpServletResponse response, final RedirectAttributes redirectAttributes) throws IOException {
try {
User user = userService.deleteUser(id);
redirectAttributes.addFlashAttribute("userStatusMessage", "Deleted User: " + user);
} catch (EntityNotFoundException e) {
response.sendError(HttpServletResponse.SC_BAD_REQUEST, e.getMessage());
return null;
}
return new ModelAndView(new RedirectView("/users"));
}
private Map<String, String> generateGenders() {
Map<String,String> genders = new HashMap<String,String>();
for (Gender gender : Gender.values()) {
genders.put(gender.toString(), gender.getDisplayName());
}
return genders;
}
}
And here is the error I get when I go to /users/add:
HTTP ERROR 500
Problem accessing /users/add. Reason:
Server Error
Caused by:
java.lang.NullPointerException
at java.util.Calendar.setTime(Calendar.java:1106)
at java.text.SimpleDateFormat.format(SimpleDateFormat.java:955)
at java.text.SimpleDateFormat.format(SimpleDateFormat.java:948)
at java.text.DateFormat.format(DateFormat.java:336)
at com.code9.data.User.toString(User.java:157)
at java.lang.String.valueOf(String.java:2854)
at java.lang.StringBuilder.append(StringBuilder.java:128)
at org.springframework.web.servlet.view.AbstractTemplateView.renderMergedOutputModel(AbstractTemplateView.java:146)
at org.springframework.web.servlet.view.AbstractView.render(AbstractView.java:263)
at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1208)
at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:992)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:939)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:936)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:827)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:812)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:533)
at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:475)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:119)
at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:514)
at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:226)
at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:920)
at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:403)
at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:184)
at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:856)
at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:117)
at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:247)
at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:151)
at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:114)
at org.eclipse.jetty.server.Server.handle(Server.java:352)
at org.eclipse.jetty.server.HttpConnection.handleRequest(HttpConnection.java:596)
at org.eclipse.jetty.server.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:1049)
at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:590)
at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:212)
at org.eclipse.jetty.server.HttpConnection.handle(HttpConnection.java:426)
at org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:510)
at org.eclipse.jetty.io.nio.SelectChannelEndPoint.access$000(SelectChannelEndPoint.java:34)
at org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:40)
at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:450)
at java.lang.Thread.run(Thread.java:744)
Any suggestions?

Answer 1

I have found the problem. It's inside toString() method of User class. I'm still not shure when it's called, because I don't call it explicitly. Sorry for inconvenience.
This is User toString() method before:
#Override
public String toString() {
return String.format("%d, %s %s, %s, %s, %s, %s", this.getId(), this.getFirstName(), this.getLastName(),
new SimpleDateFormat("yyyy-MM-dd").format(this.getBirthday()), this.getGender().getDisplayName(), this.getPersonalNumber(),
this.getEmail());
}
And this is a fix:
#Override
public String toString() {
return String.format("%d, %s %s, %s, %s, %s, %s", this.getId(), this.getFirstName(), this.getLastName(),
this.getBirthday() == null ? "" : new SimpleDateFormat("yyyy-MM-dd").format(this.getBirthday()), this.getGender().getDisplayName(), this.getPersonalNumber(),
this.getEmail());
}