Spring MVC: bind request attribute to controller method parameter

Question

In Spring MVC, it is easy to bind request parameter to method paramaters handling the request. I just use @RequestParameter("name"). But can I do the same with request attribute? Currently, when I want to access request attribute, I have to do following:

MyClass obj = (MyClass) request.getAttribute("attr_name"); 

But I really would like to use something like this instead:

@RequestAttribute("attr_name") MyClass obj 

Unfortunately, it doesn't work this way. Can I somehow extend Spring functionality and add my own "binders"?

EDIT (what I'm trying to achieve): I store currently logged user inside request attribute. So whenever I want to access currently logged user (which is pretty much inside every method), I have to write this extra line user = (User) request.getAttribute("user");. I would like to make it as short as possible, preferably inject it as a method parameter. Or if you know another way how to pass something across interceptors and controllers, I would be happy to hear it.

Answer 1

Well, I finally understood a little bit how models work and what is @ModelAttribute for. Here is my solution.

@Controller  class MyController {     @ModelAttribute("user")     public User getUser(HttpServletRequest request)      {         return (User) request.getAttribute("user");     }      @RequestMapping(value = "someurl", method = RequestMethod.GET)     public String HandleSomeUrl(@ModelAttribute("user") User user)       {         // ... do some stuff     } } 

The getUser() method marked with @ModelAttribute annotation will automatically populate all User user parameters marked with @ModelAttribute. So when the HandleSomeUrl method is called, the call looks something like MyController.HandleSomeUrl(MyController.getUser(request)). At least this is how I imagine it. Cool thing is that user is also accessible from the JSP view without any further effort.

This solves exactly my problem however I do have further questions. Is there a common place where I can put those @ModelAttribute methods so they were common for all my controllers? Can I somehow add model attribute from the inside of the preHandle() method of an Interceptor?

Answer 2

Use (as of Spring 4.3) @RequestAttribute:

@RequestMapping(value = "someurl", method = RequestMethod.GET) public String handleSomeUrl(@RequestAttribute User user) {     // ... do some stuff } 

or if the request attribute name does not match the method parameter name:

@RequestMapping(value = "someurl", method = RequestMethod.GET) public String handleSomeUrl(@RequestAttribute(name="userAttributeName") User user) {     // ... do some stuff }