如何从视图范围获取豆类 [英] how to get beans from view scope

问题描述

我想问是否将托管bean放置在会话范围内，然后将其存储在会话中'就像我是否有这样的bean

I want to ask if i place my managed bean in session scope, then it is stored in session' Like if i have a bean like this

@ManagedBean
@SessionScoped
public class SessionScopedBean implements Serializable {

    .......

} //end of class SessionScopedBean

然后将其存储在会话中，在我的会话中，我可以使用

Then it stored in the session, and during my session i can get it using

session.getAttribut("SessionScopedBean");

这将为我提供SessionScopedBean对象，并且当会话被销毁时，我将为null.现在，我想问一下是否在Scope中有我的bean，然后如何获取它.喜欢

This will give me the SessionScopedBean Object, and when session will get destroy, i will get null. Now i want to ask if i have my bean in view Scope, then how can i get it. Like

@ManagedBean
@ViewScoped
public class ViewScopedBean implements Serializable {

    .......

} //end of class ViewScopedBean

现在如果视图是持久的，那么这个bean处于视图状态，并且当视图改变时，这个bean将被破坏.现在我想问一下，如果视图持久化，我该如何从视图状态中获取这个bean.喜欢

Now if the view is persist then this bean is in the view state, and when view changes, this bean will get destroy.Now i want to ask how can i get this bean from view state, if the view persist. Like

view.getAttrubute("ViewScopedBean");  //just a code. No actual implementation.

谢谢

推荐答案

它们存储在视图中，

They're stored in the view map as available by UIViewRoot#getViewMap():

Map<String, Object> viewMap = FacesContext.getCurrentInstance().getViewRoot().getViewMap();
ViewScopedBean viewScopedBean = (ViewScopedBean) viewMap.get("viewScopedBean");
// ...

等效地，您还应该使用会话映射抽象，它可以通过

Equivalently, you should be using the session map abstraction as well which is available by ExternalContext#getSessionMap() (you ultimately want to have zero javax.servlet import declarations throughout your JSF code):

Map<String, Object> sessionMap = FacesContext.getCurrentInstance().getExternalContext().getSessionMap();
SessionScopedBean sessionScopedBean = (SessionScopedBean) sessionMap.get("sessionScopedBean");
// ...

另请参见:

• 在任何与Servlet相关的类中按名称获取JSF托管bean

See also:

• Get JSF managed bean by name in any Servlet related class

无关与具体问题无关，这可能不是最好的方法.如果可能，请查看 @ManagedProperty .

Unrelated to the concrete problem, this may not be the best way. Look at @ManagedProperty if possible.

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