使用JSF 2.2时，将在每个回发请求上重新创建@ViewScoped bean [英] @ViewScoped bean recreated on every postback request when using JSF 2.2
问题描述
我遇到的问题类似于这篇文章和@BalusC的答案以及3种解决方案，但:
- 我没有使用提到的EL表达式
- 我不想采用第二种解决方案(像这样对我来说足够复杂)
- 并将部分状态保存设置为false.
我的代码如下:
index.xhtml:
<?xml version="1.0" encoding="windows-1256" ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:p="http://primefaces.org/ui"
xmlns:ui="http://java.sun.com/jsf/facelets"
xmlns:f="http://java.sun.com/jsf/core">
<h:head>
<title>Insert title here</title>
</h:head>
<h:body>
<h:form>
<p:panelMenu id="westMenu">
<p:submenu id="sub1" label="System Monitor">
<p:menuitem id="menu1" value="live monitoring"
action="#{menusBean.activateMenu('sub1_menu1')}"
update=":centerPane,westMenu"
disabled="#{menusBean.active['sub1_menu1']}" />
<p:menuitem id="menu2" value="reports"
action="#{menusBean.activateMenu('sub1_menu2')}"
update=":centerPane,westMenu"
disabled="#{menusBean.active['sub1_menu2']}" />
</p:submenu>
<p:submenu id="sub2" label="Charging System Nodes" />
<p:submenu id="sub3" label="Additional Nodes" />
</p:panelMenu>
</h:form>
<h:panelGroup id="centerPane">
...
</h:panelGroup>
</h:body>
</html>
MenusBean.java:
package menus;
import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;
import javax.faces.view.ViewScoped;
@ManagedBean
@ViewScoped
public class MenusBean implements Serializable{
private static final long serialVersionUID = -7793281454064343472L;
private String mainPage="sub1_menu1";
private Map<String, Boolean> active;
public MenusBean(){
System.out.println("MenusBean created");
active = new HashMap<>();
active.put(mainPage, true);
active.put("sub1_menu2", false);
}
public boolean activateMenu(String page){
active.put(mainPage, false);
active.put(page, true);
mainPage = page;
for (Map.Entry<String, Boolean> e : active.entrySet())
System.out.println(e.getKey()+":"+e.getValue());
return true;
}
public Map<String, Boolean> getActive() {
return active;
}
}
执行后，我得到:
MenusBean created MenusBean created MenusBean created
这是怎么引起的，我该如何解决?
此
import javax.faces.view.ViewScoped;
是 JSF 2.2引入的CDI特定注释，旨在与特定于CDI的bean管理注释@Named结合使用.
但是，您正在使用特定于JSF的bean管理注释@ManagedBean.
import javax.faces.bean.ManagedBean;
然后，您应该使用由相同的 javax.faces.bean软件包.正确的 @ViewScoped 在那儿:
import javax.faces.bean.ManagedBean;
import javax.faces.bean.ViewScoped;
@ManagedBean
@ViewScoped
public class MenusBean implements Serializable{
如果使用错误的组合，则该Bean的行为与@RequestScoped Bean相同，并在每次调用时重新创建.
或者，如果您的环境支持CDI(带有Weld，OpenWebBeans等的GlassFish/JBoss/TomEE)，那么您也可以将@ManagedBean替换为@Named:
import javax.inject.Named;
import javax.faces.view.ViewScoped;
@Named
@ViewScoped
public class MenusBean implements Serializable{
建议改用CDI. JSF特定的bean管理注释是将来的JSF/Java EE版本中不推荐使用的注释，因为一切都在朝着CDI缓慢/统一发展.
I'm having an issue similar to this post and the answer from @BalusC with 3 solutions but:
- I'm not using of the mentioned EL expressions
- I don't want to go with the second solution (it's complex enough for me like this)
- and partial state saving is set to false.
My code is as follows:
index.xhtml:
<?xml version="1.0" encoding="windows-1256" ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:p="http://primefaces.org/ui"
xmlns:ui="http://java.sun.com/jsf/facelets"
xmlns:f="http://java.sun.com/jsf/core">
<h:head>
<title>Insert title here</title>
</h:head>
<h:body>
<h:form>
<p:panelMenu id="westMenu">
<p:submenu id="sub1" label="System Monitor">
<p:menuitem id="menu1" value="live monitoring"
action="#{menusBean.activateMenu('sub1_menu1')}"
update=":centerPane,westMenu"
disabled="#{menusBean.active['sub1_menu1']}" />
<p:menuitem id="menu2" value="reports"
action="#{menusBean.activateMenu('sub1_menu2')}"
update=":centerPane,westMenu"
disabled="#{menusBean.active['sub1_menu2']}" />
</p:submenu>
<p:submenu id="sub2" label="Charging System Nodes" />
<p:submenu id="sub3" label="Additional Nodes" />
</p:panelMenu>
</h:form>
<h:panelGroup id="centerPane">
...
</h:panelGroup>
</h:body>
</html>
MenusBean.java:
package menus;
import java.io.Serializable;
import java.util.HashMap;
import java.util.Map;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.SessionScoped;
import javax.faces.view.ViewScoped;
@ManagedBean
@ViewScoped
public class MenusBean implements Serializable{
private static final long serialVersionUID = -7793281454064343472L;
private String mainPage="sub1_menu1";
private Map<String, Boolean> active;
public MenusBean(){
System.out.println("MenusBean created");
active = new HashMap<>();
active.put(mainPage, true);
active.put("sub1_menu2", false);
}
public boolean activateMenu(String page){
active.put(mainPage, false);
active.put(page, true);
mainPage = page;
for (Map.Entry<String, Boolean> e : active.entrySet())
System.out.println(e.getKey()+":"+e.getValue());
return true;
}
public Map<String, Boolean> getActive() {
return active;
}
}
When executed, I get:
MenusBean created MenusBean created MenusBean created
How is this caused and how can I solve it?
This,
import javax.faces.view.ViewScoped;
is the JSF 2.2-introduced CDI-specific annotation, intented to be used in combination with CDI-specific bean management annotation @Named.
However, you're using the JSF-specific bean management annotation @ManagedBean.
import javax.faces.bean.ManagedBean;
You should then be using any of the scopes provided by the very same javax.faces.bean package instead. The right @ViewScoped is over there:
import javax.faces.bean.ManagedBean;
import javax.faces.bean.ViewScoped;
@ManagedBean
@ViewScoped
public class MenusBean implements Serializable{
If you use the wrong combination, the bean behaves as a @RequestScoped bean and be recreated on each call.
Alternatively, if your environment supports CDI (GlassFish/JBoss/TomEE with Weld, OpenWebBeans, etc), then you could also replace @ManagedBean by @Named:
import javax.inject.Named;
import javax.faces.view.ViewScoped;
@Named
@ViewScoped
public class MenusBean implements Serializable{
It's recommended to move to CDI. The JSF-specific bean management annotations are candidate for deprecation in future JSF / Java EE versions as everything is slowly moving/unifying towards CDI.
这篇关于使用JSF 2.2时，将在每个回发请求上重新创建@ViewScoped bean的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
