@ModelAttribute在一个方法 [英] @ModelAttribute in a method

问题描述

想象一下这样的代码：

@RequestMapping(value="/users", method=RequestMethod.GET)
public String list(Model model) {
    ...
}

@InitBinder("user")
public void initBinder(WebDataBinder binder) {
    binder.setDisallowedFields("password"); // Don't allow user to override the value
}

@ModelAttribute("user")
public User prepareUser(@RequestParam("username") String username){
    ...
}

@RequestMapping(value="/user/save", method=RequestMethod.POST)
public String save(@ModelAttribute("user") User user, Model model) {        
    ...
}

我使用一个初始化绑定，以避免一个字段可以绑定，我标记一个方法（prepareUser（））与@ModelAttribute，以准备我的用户对象绑定之前。所以当我调用/ user / save initBinder（）和prepareUser（）被执行时。

I use an init binder to avoid that a field can be binded and I mark a method (prepareUser()) with @ModelAttribute to prepare my User object before it is binded. So when I invoke /user/save initBinder() and prepareUser() are executed.

我已经在@InitBinder和@ModelAttribute中设置了user，所以Spring-MVC可以理解，这种方法应该只在使用@ModelAttribute（user）执行方法之前应用。

I have set "user" in both @InitBinder and @ModelAttribute so Spring-MVC could understand that this methods should only be applied before executing a method with @ModelAttribute("user").

问题是，使用@ModelAttribute（user ）在此控制器的每个映射方法之前执行。例如，如果我调用/用户prepareUser在list（）方法之前执行。如何使这个准备工作只在save（）方法之前执行，所有方法都在同一个控制器中？

The problem is that the method annotated with @ModelAttribute("user") is executed before every mapped method of this controller. For example if I invoke /users prepareUser is executed before list() method. How can I make that this preparer is only executed before save() method having all the methods in the same controller?

谢谢

推荐答案

这不是真正的 @ModelAttribute 。如果使用它作为一个方法参数，它将注释的参数放入模型中（没关系）。如果你把它放在一个方法上，那么每次都会调用控制器中每个方法都可以访问的参考数据。

That's not really what @ModelAttribute is for. If you use it as a method parameter, it puts the annotated parameter into the model (that's fine). If you put it on a method, it's called every time to provide reference data that every method in the controller should have access to.

如果你想控制建筑物您的用户对象，您有几个选项。对我来说最明显的是：

If you want to take control of building up your User object, you have several options. The two that are most obvious to me are:

1. 使用您的InitBinder方法添加一个新的自定义编辑器（PropertyEditor类），用于构建用户对象，


2. 使用转换服务在Spring 3中将字符串用户名转换为用户对象。

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