尽管呈现＝“假"，但是总是评估h:dataTable的内容. [英] Although rendered="false", content of a h:dataTable is always evaluated
问题描述
我遇到了JSF 2.0的HtmlDataTable问题.在我的网页上，我有一个h:dataTable和一些其他内容，这些内容仅在用户登录后才能呈现.
I have got a problem with the HtmlDataTable of JSF 2.0. On my web page, i have got a h:dataTable and some other content, which should only be rendered if the user is logged in.
HtmlDataTable的内容是从数据库中加载的.尽管在用户未登录时未呈现h:dataTable，但仍会评估其内容.
The content of the HtmlDataTable is loaded from a database. Although the h:dataTable is not rendered when the user is not logged in, the content is still evaluated.
这是网页的代码:
<h:panelGroup rendered="#{userBean.loggedIn}">
<h:dataTable value="#{xxxBean.allXxx}"
var="c">
<h:column>
<h:outputText value="#{c.name}"/>
</h:column>
</h:dataTable>
<!-- some other content -->
</h:panelGroup>
在getAllXxx()方法中，我正在记录该方法的调用.但是，如果未呈现h:dataTable(以及所有其他内容)，则仍将调用getAllXxx()方法.
In the getAllXxx() method I am logging the call of the method. But also if the h:dataTable (and all the other content) is not rendered, the getAllXxx() method is still called.
我尝试使用c:if代替h:panelGroup.可以，但是随后在登录过程中出现问题，因此这不是合适的解决方案.
I tried to use c:if instead of the h:panelGroup. That would work, but then I get issues during the login-process, so this is no suitable solution.
有人知道如何解决此问题吗?预先感谢.
Does anyone know how to fix this? Thanks in advance.
推荐答案
使用以下 SSCCE .
test.xhtml
<!DOCTYPE html>
<html lang="en"
xmlns="http://www.w3.org/1999/xhtml"
xmlns:h="http://java.sun.com/jsf/html">
<h:head>
<title>SO question 4774516</title>
</h:head>
<h:body>
<h:panelGroup rendered="#{param.show}">
<h:dataTable value="#{bean.list}" var="item">
<h:column>#{item}</h:column>
</h:dataTable>
</h:panelGroup>
</h:body>
</html>
com.example.Bean
package com.example;
import java.util.Arrays;
import java.util.List;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.RequestScoped;
@ManagedBean
@RequestScoped
public class Bean {
private List<String> list = Arrays.asList("one", "two", "three");
public List<String> getList() {
System.out.println("getList() called");
return list;
}
}
打开 http://localhost:8080/playground/test.jsf 不显示任何标准输出行.打开 http://localhost:8080/playground/test.jsf?show = true 显示它们.
Opening http://localhost:8080/playground/test.jsf doesn't show any stdout lines. Opening http://localhost:8080/playground/test.jsf?show=true shows them.
您的问题是由其他原因引起的.这可能是您的JSF实现中的错误，或者您只是误解了该过程.例如，实际上可以是回发请求，其中，在应用请求值阶段期间调用吸气剂，而#{userBean.loggedIn}的结果仅在调用动作阶段期间进行更改.否则吸气剂会被其他东西调用.
Your problem is caused by something else. Either it's a bug in your JSF implementation or you just misinterpreted the procedure. It can for example actually be a postback request wherein the getter is been called during apply request values phase and the outcome of #{userBean.loggedIn} is only changed during invoke action phase. Or the getter is called by something else.
这篇关于尽管呈现＝“假"，但是总是评估h:dataTable的内容.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！
