当SpringMVC中的@SessionAttributes什么时候被删除？ （带代码示例） [英] When do @SessionAttributes in SpringMVC get removed? (With code sample)

问题描述

@SessionAttributes在什么确切的情况下被清除？我试图在页面中使用两个模型时发现了一些混乱的行为。

Under what exact circumstances do @SessionAttributes get cleared? I've discovered some confusing behaviour when trying to use two models in a page.

当我使用此控制器执行GET后接POST时...

When I do a GET followed by a POST using this controller...

@Controller
@RequestMapping("/myPage*")
@SessionAttributes(value = {"object1", "object2"})
public class MyController {

  @RequestMapping(method = RequestMethod.GET)
  public String get(Model model) {
      model.addAttribute("object1", new Object1());
      model.addAttribute("object2", new Object2());
      return "myPage";
  }

  @RequestMapping(method = RequestMethod.POST)
  public String post(@ModelAttribute(value = "object1") Object1 object1) {
      //do something with object1
      return "myPage";
  }
}

... object2从模型中清除。它不再作为@SessionAttribute存在，不能在我的视图页面上访问。

...object2 gets cleared from the Model. It no longer exists as a @SessionAttribute and cannot be accessed on my view page.

但是如果第二个方法的签名被修改为this ...

However if the signature of the second method is modified to this...

public String post(@ModelAttribute(value = "object1") Object1 object1,
                   @ModelAttribute(value = "object2") Object2 object2) {

...然后object2不会从模型中清除，

...then object2 does not get cleared from the model and is available on my view page.

@SessionAttributes的javadoc说：

The javadoc for @SessionAttributes says:

...属性将被删除一次
处理程序指示完成其对话会话的
。

... attributes will be removed once the handler indicates completion of its conversational session.

但我不

任何人都可以解释这个行为，或者是一个错误？

Can anyone explain this behaviour or is it a bug?

推荐答案

您表示通过调用

SessionStatus.setComplete

public void post(...., SessionStatus status) {
  status.setComplete();
}

也就是说，我不明白为什么你应该放弃一个模型属性

That said, I don't see why you should be loosing one model attribute and not the other.

您尝试过以下操作：

@ModelAttribute("object1")
public Object object1() { return new Object(); }

@ModelAttribute("object2")
public Object object2() { return new Object(); }

看看如何比较手动将属性放在模型中。

And see how that compares to putting the attributes in the model by hand.

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