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 在什么确切情况下被清除?在尝试在页面中使用两个模型时，我发现了一些令人困惑的行为.

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 和 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 存在并且无法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.

但是如果把第二种方法的签名修改成这样...

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 不会从模型中清除并且在我的视图页面上可用.

...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它的会话会话.

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

但是我没有看到我是如何在第一个示例中指示会话会话完成的，而在第二个示例中却没有.

But I don't see how I have indicated completion of the conversational session in the first example but not in the second example.

任何人都可以解释这种行为还是它是一个错误?

Can anyone explain this behaviour or is it a bug?

推荐答案

您通过调用来表示对话的完成

You indicate completion of the conversation by calling

SessionStatus.setComplete

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

也就是说，我不明白为什么您应该丢失一个模型属性而不是另一个.

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

你有没有试过做这样的事情:

Have you tried doing something like:

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

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

看看这与手动将属性放入模型相比如何.

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

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