问题
I created a webpage, which checks the view-parameter from the URL, and calls the init-method of a bean to retrieve that user. The fields on that page are then filled with the information of that user.
But something is going wrong.
My Facelets page:
<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:ui="http://java.sun.com/jsf/facelets"
xmlns:f="http://java.sun.com/jsf/core">
<h:head>
<title>Tweetpage of #{userBean.getName()}</title>
</h:head>
<h:body>
<f:metadata>
<f:viewParam name="user" value="#{userBean.name}" />
<f:event type="preRenderView" listener="#{userBean.init}" />
</f:metadata>
<h:commandButton value="Login" action="#{loginBean.login()}" id="login" />
<div class="namebox">
<label>User: #{userBean.name} </label> <br/>
<br/>
</div>
</h:body>
</html>
And the UserBean.java:
package beans;
import ...
@Named
@RequestScoped
public class UserBean implements Serializable {
private String userName;
private String name;
private String bio;
private String web;
private Collection<Tweet> tweets;
private Collection<User> followers;
private User user;
@Inject
private @Named(value = "kwetterService")
KwetterService service;
@PostConstruct
public void init(ComponentSystemEvent event) throws AbortProcessingException {
System.out.println(name);
user = service.find(name);
if (user != null)
{
name = user.getName();
bio = user.getBio();
web = user.getWeb();
tweets = user.getTweets();
followers = user.getFollowing();
}
}
}
Since the System.out.println(name) isn't called, I don't think the webpage is calling the init. If I start the webpage without URL-adaptions (http://localhost:8080/KwetterJSF/), I get the following error message:
WELD-000049 Unable to invoke [method] @PostConstruct public beans.UserBean.init(ComponentSystemEvent) on beans.UserBean@3c836d3d
And if I add parameters (http://localhost:8080/KwetterJSF/index.xhtml?user=Sjaak), I get the following:
User: #{userBean.name}
I'm not too experienced with this, and I can't figure it out even though I researched a bit myself. Does anybody know the solution?
回答1:
There are 2 problems.
First, you're mixing <f:event> with @PostConstruct.
The @PostConstruct can only be a method which does not take arguments. That explains the exception. Get rid of that annotation. It runs too early anyway when view parameters play a role.
See also:
- ViewParam vs @ManagedProperty(value = "#{param.id}")
Second, in order to properly execute a JSF page, you need to make sure that the URL pattern as appears in browser's address bar matches the one of the FacesServlet as registered in /WEB-INF/web.xml. So if it's for example *.jsf, then you need to make sure that you open the page by /page.jsf URL, not /page.xhtml. If you don't do that, JSF tags/components and EL expressions won't be recognized and thus be treated as "plain text".
Much better is however to just map the FacesServlet directly on an URL pattern of *.xhtml. This saves you from virtual URL headache.
- JSF Facelets: Sometimes I see the URL is .jsf and sometimes .xhtml. Why?
来源：https://stackoverflow.com/questions/12787325/viewparam-event-going-wrong