我真的不明白为什么这个简单的东西不起作用。我可以看到我设置了每次设置一个属性时都会调用构造函数。问题是，当我到达 sendInvitation 方法时，所有邀请电子邮件都为空。
@Named(value = "adminBean")
@RequestScoped
public class AdminBean implements Serializable {
private String inviteEmail1;
private String inviteEmail2;
private String inviteEmail3;
private BasicUser administrator;
@EJB
private MessageBeanRemote messageBean3;
/** Creates a new instance of AdminBean */
public AdminBean() {
HttpSession session = (HttpSession) FacesContext.getCurrentInstance().
getExternalContext().getSession(true);
LoginBean loginBean = (LoginBean) session.getAttribute("loginBean");
administrator = loginBean.getUser();
}
public String getInviteEmail1() {
return inviteEmail1;
}
public void setInviteEmail1(String inviteEmail) {
this.inviteEmail1 = inviteEmail;
}
public String getInviteEmail2() {
return inviteEmail2;
}
public void setInviteEmail2(String inviteEmail) {
this.inviteEmail2 = inviteEmail;
}
public String getInviteEmail3() {
return inviteEmail3;
}
public void setInviteEmail3(String inviteEmail) {
this.inviteEmail3 = inviteEmail;
}
public void sendInvitations() {
...
}
}
使用此 bean 的页面是一个组件，它是另一个页面的一部分:
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:ui="http://java.sun.com/jsf/facelets">
<ui:component id="adminComp">
<h3>Adminstration page</h3>
<h:form id="inviteForm">
<h:panelGrid columns="1">
Invite new members to your group. Type in their emails in the fields below.
<h:inputText id="email1" value="#{adminBean.inviteEmail1}" size="40"/>
<h:inputText id="email2" value="#{adminBean.inviteEmail2}" size="40"/>
<h:inputText id="email3" value="#{adminBean.inviteEmail3}" size="40"/>
<h:commandButton value="invite" action="#{adminBean.sendInvitations}"/>
</h:panelGrid>
</h:form>
</ui:component>
</html>
adminBean 实际上被初始化了很多次，看起来有点奇怪。 “Constructor”是adminBean构造函数，“Get 1”是getInviteEmail1等等。
INFO: START PHASE RESTORE_VIEW 1
INFO: END PHASE RESTORE_VIEW 1
INFO: START PHASE APPLY_REQUEST_VALUES 2
INFO: END PHASE APPLY_REQUEST_VALUES 2
INFO: START PHASE PROCESS_VALIDATIONS 3
INFO: Constructor
INFO: Constructor
INFO: Constructor
INFO: Constructor
INFO: Constructor
INFO: Constructor
INFO: Get 2
INFO: Constructor
INFO: Constructor
INFO: Constructor
INFO: Get 3
INFO: END PHASE PROCESS_VALIDATIONS 3
INFO: START PHASE UPDATE_MODEL_VALUES 4
INFO: Constructor
INFO: Set 1
INFO: Constructor
INFO: Set 2
INFO: Constructor
INFO: Set 3
INFO: END PHASE UPDATE_MODEL_VALUES 4
INFO: START PHASE INVOKE_APPLICATION 5
INFO: Constructor
SEVERE: NullPointerException....
INFO: END PHASE INVOKE_APPLICATION 5
INFO: START PHASE RENDER_RESPONSE 6
INFO: Constructor
INFO: Constructor
INFO: Get 2
INFO: Constructor
INFO: Get 3
INFO: END PHASE RENDER_RESPONSE 6
如有任何帮助，我们将不胜感激。
最佳答案
我不知道 @Named 东西在那里做什么，但是每次通过值表达式访问 bean 时都会构造 bean，这是不正常的。它应该只在 HTTP 请求开始时构造一次。可能 @Named 后面的配置是错误的。
尝试使用 @ManagedBean 以 JSF 方式声明 Bean，并确保 @RequestScoped 也来自 javax.faces.bean 包。
import javax.faces.bean.ManagedBean;
import javax.faces.bean.RequestScoped;
@ManagedBean
@RequestScoped
public class AdminBean implements Serializable {
// ...
}
除了这个问题之外，不推荐您获取 session 作用域 bean 的方法。正常的 JSF 方式如下:
@ManagedProperty(value="#{loginBean}")
private LoginBean loginBean;
如果需要，可以使用以下 getter
public BasicUser getAdministrator() {
return loginBean.getUser();
}
关于java - Jsf 属性未保存，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/3950243/