Although rendered=“false”, content of a h:dataTable is always evaluated

问题

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.

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.

Here is the code of the web page:

<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>

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.

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.

Does anyone know how to fix this? Thanks in advance.

回答1:

Can't reproduce your problem on Mojarra 2.0.3 on Tomcat 7.0.5 with the following 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;
    }

}

Opening http://localhost:8080/playground/test.jsf doesn't show any stdout lines. Opening http://localhost:8080/playground/test.jsf?show=true shows them.

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.

来源：https://stackoverflow.com/questions/4774516/although-rendered-false-content-of-a-hdatatable-is-always-evaluated

标签

java

jsf

jsf-2

rendered-attribute