春：适时/后期绑定@ModelAttribute

Question

我使用下面的代码绑定的用户模型[待视图/ JSP使用]：

@ModelAttribute("users") 
public Collection<User> populateUsers() { 
    return userService.findAllUsers(); 
} 

但有时我只需要加载几个用户有特殊的作用，这我用下面的代码尝试：

int role = 2; //this is being set in a Controller within a method @RequestMapping(method = RequestMethod.GET) public String list(
@ModelAttribute("users") 
public Collection<User> populateUsers() { 
    if(role == 2) 
     return userService.findAllUsersByRole(role); 
    else 
     return userService.findAllUsers(); 
} 

但populateUsers总是被调用在控制器开始，之前的角色列表中的方法设置，你能请帮助我如何设置用户[类似于后期绑定]

个

问候

- 添加代码

@Controller 
@RequestMapping("/users") 
public class UserController { 

@Autowired 
UserService userService; 

@RequestMapping(method = RequestMethod.POST) 
public String create(@Valid User user, BindingResult bindingResult, 
     Model uiModel, HttpServletRequest httpServletRequest) { 
    if (bindingResult.hasErrors()) { 
     uiModel.addAttribute("user", user); 
     addDateTimeFormatPatterns(uiModel); 
     return "users/create"; 
    } 
    uiModel.asMap().clear(); 
    userService.saveUser(user); 
    return "redirect:/users/" 
      + encodeUrlPathSegment(user.getId().toString(), 
        httpServletRequest); 
} 

@RequestMapping(params = "form", method = RequestMethod.GET) 
public String createForm(Model uiModel) { 
    uiModel.addAttribute("user", new User()); 
    addDateTimeFormatPatterns(uiModel); 
    return "users/create"; 
} 

@RequestMapping(value = "/{id}", method = RequestMethod.GET) 
public String show(@PathVariable("id") Long id, Model uiModel) { 
    addDateTimeFormatPatterns(uiModel); 
    uiModel.addAttribute("user", userService.findUser(id)); 
    return "users/show"; 
} 

@RequestMapping(value = "/{id}", params = "form", method = RequestMethod.GET) 
public String updateForm(@PathVariable("id") Long id, Model uiModel) { 
    uiModel.addAttribute("user", userService.findUser(id)); 
    addDateTimeFormatPatterns(uiModel); 
    return "users/update"; 
} 

@ModelAttribute("users") 
public Collection<User> populateUsers() { 
    return userService.findAllUsers(); 
} 

@ModelAttribute("userroles") 
public Collection<UserRole> populateUserRoles() { 
    return Arrays.asList(UserRole.class.getEnumConstants()); 
} 

void addDateTimeFormatPatterns(Model uiModel) { 
    uiModel.addAttribute(
      "user_modified_date_format", 
      DateTimeFormat.patternForStyle("M-", 
        LocaleContextHolder.getLocale())); 
} 

} 

@PathVariable（ “ID”）长的id是我需要populateUsers的ID，希望这是显而易见的。

Answer 1

设置在所要求的方法模型属性已经解决了我的问题：

model.addAttribute("users", return userService.findAllUsersByRole(role)); 

谢谢！

Answer 2

如果角色在当前请求中，则此方法将角色绑定到变量角色。

 @ModelAttribute("users") 
     public Collection<User> populateUsers(@RequestParam(required=false) Integer role) { 
      if(role != null && role == 2) 
       return userService.findAllUsersByRole(role); 
      else 
       return userService.findAllUsers(); 
     }