Spring MVC：将请求属性绑定到控制器方法参数 [英] Spring MVC: bind request attribute to controller method parameter

问题描述

在Spring MVC中，很容易将请求参数绑定到处理请求的方法参数。我只使用 @RequestParameter（name）。但是我可以对请求属性执行相同的操作吗？目前，当我想访问请求属性时，我必须执行以下操作：

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");

但我真的想用这样的东西：

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

@RequestAttribute("attr_name") MyClass obj

不幸的是，这种方式不起作用。我可以以某种方式扩展Spring功能并添加我自己的绑定器吗？

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

编辑 （我正在努力实现的目标）：我将当前登录的用户存储在请求属性中。因此，每当我想访问当前登录的用户（这几乎都在每个方法中）时，我必须写这个额外的行 user =（User）request.getAttribute（user）; 。我想尽量缩短它，最好将它作为方法参数注入。或者如果你知道如何通过拦截器和控制器传递某些东西，我会很高兴听到它。

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.

推荐答案

嗯，我终于理解了模型的工作原理以及 @ModelAttribute 的用途。这是我的解决方案。

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
    }
}

标有 @ModelAttribute 注释的 getUser（）方法将自动填充所有用户用户标有 @ModelAttribute 的参数。因此，当调用HandleSomeUrl方法时，调用看起来像 MyController.HandleSomeUrl（MyController.getUser（request））。至少这是我的想象。很酷的是，用户也可以从JSP视图中访问而无需任何进一步的努力。

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.

这解决了我的问题，但我还有其他问题。是否有一个常见的地方我可以放置那些 @ModelAttribute 方法，以便它们对我的所有控制器都是通用的？我可以以某种方式从拦截器的 preHandle（）方法内部添加模型属性吗？

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?

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