@SessionAttributes

@SessionAttributes 用于在请求之间将模型属性存储在 WebSession 中。这是一种类型级注解，用于声明特定控制器使用的会话属性。这通常列出模型属性的名称或模型属性的类型，这些属性应该透明地存储在会话中，以便后续请求访问。

@SessionAttributes is used to store model attributes in the WebSession between requests. It is a type-level annotation that declares session attributes used by a specific controller. This typically lists the names of model attributes or types of model attributes that should be transparently stored in the session for subsequent requests to access.

请考虑以下示例：

Consider the following example:

Java
@Controller
@SessionAttributes("pet") 1
public class EditPetForm {
	// ...
}
1 Using the @SessionAttributes annotation.
Kotlin
@Controller
@SessionAttributes("pet") (1)
class EditPetForm {
	// ...
}
2 Using the @SessionAttributes annotation.

在第一个请求中，当名为 pet 的模型属性被添加到模型时，它会自动提升并保存在 WebSession 中。它会一直保留在那里，直到另一个控制器方法使用 SessionStatus 方法参数清除存储，如下例所示：

On the first request, when a model attribute with the name, pet, is added to the model, it is automatically promoted to and saved in the WebSession. It remains there until another controller method uses a SessionStatus method argument to clear the storage, as the following example shows:

Java
@Controller
@SessionAttributes("pet") (1)
public class EditPetForm {

	// ...

	@PostMapping("/pets/{id}")
	public String handle(Pet pet, BindingResult errors, SessionStatus status) { (2)
		if (errors.hasErrors()) {
			// ...
		}
			status.setComplete();
			// ...
		}
	}
}
1 Using the @SessionAttributes annotation.
2 Using a SessionStatus variable.
Kotlin
@Controller
@SessionAttributes("pet") (1)
class EditPetForm {

	// ...

	@PostMapping("/pets/{id}")
	fun handle(pet: Pet, errors: BindingResult, status: SessionStatus): String { (2)
		if (errors.hasErrors()) {
			// ...
		}
		status.setComplete()
		// ...
	}
}
3 Using the @SessionAttributes annotation.
4 Using a SessionStatus variable.