JSF最佳传递参数的方法 [英] JSF best Way to pass parameters
问题描述
我目前正在使用JSF，但是由于我是一个老旧而笨拙的php-dev，所以我总是把请求的GET-Parameters弄乱了. (在PHP中，您可以使用$_GET["paramname"]数组随时访问请求参数.
i'm currently working with JSF, but since i'm a old and grouchy php-dev i always mess up with the GET-Parameters of an request. (In PHP you can access the request Paramerts whenever you want, using the $_GET["paramname"] Array.
现在，我正在开发一个用户管理系统. (CRUD)通常，我会列出所有可用用户的列表，并提供诸如编辑/删除之类的选项.然后，编辑链接指向http:\\localhost\editUser.xhtml?userId=5.
Now, i'm working on an User Managment System. (CRUD) Usually i go with a list of all available users, having options like edit / delete. The edit link is then pointing to http:\\localhost\editUser.xhtml?userId=5 for example.
我还有一个名为UserEditController的控制器，该控制器基本上持有用户实体并调用更新.
I have also an Controller called UserEditController which basically holds the user entity and invokes the update.
因此，在此Controller内，我正在使用@PostConstruct注释从DataService加载ID为5的用户并将其存储在属性中.
So, inside this Controller I'm using the @PostConstruct Annotation to load the user with the id 5 from the DataService and store it inside a property.
这里的问题是:Wenn在APPLY_REQUEST_VALUES -Phase im中输入PostConstruct-Method无法访问请求的Faces Context参数映射(将对userId返回null)
Problem here is: Wenn entering PostConstruct-Method in the APPLY_REQUEST_VALUES-Phase im not able to access the request Parameter Map of Faces Context (Will return null for userId)
控制器(简体):
@Named
@RequestScoped
UserEditController{
@Inject
private UserDataService userDataService;
private User currentUser;
@PostConstruct
public void initValues(){
String id = FacesContext.getCurrentInstance().getExternalContext().getRequestParameterMap().get("userId");
this.currentUser = userDataService.getUserById(id);
}
public String saveCurrentUser(){
userDataService.updateUser(this.currentUser);
return "userManagement"; //return to overview after saving
}
//getter and setter
}
这可以按预期进行.现在，所有的表单域"都已绑定到用户的属性，例如#{userEditController.currentUser.forename}等.
This works as intened. All the Form-Fields now are bound to user's properties like #{userEditController.currentUser.forename} etc.
我现在添加了具有动作属性{userEditController.saveCurrentUser()}
I now added a save button with action attribute {userEditController.saveCurrentUser()}
但是脚本随后进入APPLY_REQUEST_VALUES-阶段，并再次调用UserEditController的initValues.
However the script then enters the APPLY_REQUEST_VALUES-Phase And the UserEditController's initValues is called again.
- 尝试访问RequestParameterMap时，这会导致nullpointer异常
- 显然，我不想在保存用户之前重新加载用户:-)
这听起来像是一个愚蠢的问题，但是我认为我在搞混PHP样式和JSF样式之间来处理事情.
This sounds like a stupid question but i think i'm messing up between the PHP-Style and the JSF-Style to handle things.
任何帮助将不胜感激.
推荐答案
将用户(或用户ID)传递到BackingBean的常用方法是使用以下选项之一:
The common way to pass the user (or userID) to your BackingBean, is using one of the following options:
http ://www.mkyong.com/jsf2/4-ways-to-pass-parameter-from-jsf-page-to-backing-bean/
我认为主要问题是您的bean是@RequestScoped.如果在编辑页面上按保存按钮，则将发送新请求，因此将创建请求范围的Bean的新实例.只需将您的bean更改为@ViewScoped.
I think the main problem is that your bean is @RequestScoped. If you push the save button on your edit-page you are sending a new request, so a new instance of a request scoped bean will be created. Just change your bean to @ViewScoped.
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