JSF 传递 Bean 来查看失败

Question

我正在尝试编写一个简单的 JSF 页面，该页面最初包含两个子视图/包含，并将支持 bean 传递给其中一个包含，因为包含是可重用的（并且可能在更大的应用程序中包含不止一次） .

这是相关代码：

page1.xhtml

<ui:composition xmlns="http://www.w3.org/1999/xhtml"
    xmlns:h="http://xmlns.jcp.org/jsf/html"
    xmlns:p="http://xmlns.jcp.org/jsf/passthrough"
    xmlns:ui="http://xmlns.jcp.org/jsf/facelets"
    xmlns:f="http://xmlns.jcp.org/jsf/core"
    xmlns:pf="http://primefaces.org/ui"
    xmlns:c="http://java.sun.com/jsp/jstl/core"
    template="templates/template1.xhtml">

    <ui:define name="subheader">
        Person Details
    </ui:define>

    <ui:define name="bodyContent">
        <h:form>
            <c:forEach items="#{page1Bean.blockNames}" var="blockName">
                <c:choose>
                    <c:when test="#{blockName} eq 'block1'">
                        <ui:include src="block1.xhtml" >
                            <ui:param name="bean" value="#{page1Bean.myBean}"/>
                        </ui:include>
                    </c:when>
                    <c:otherwise>
                        <ui:include src="#{blockName}.xhtml" />
                    </c:otherwise>
                </c:choose>
            </c:forEach>
            <pf:commandButton value="Ajax Button" action="#{page1Bean.ajaxSubmit()}"/>
        </h:form>

    </ui:define>
</ui:composition>

block1.xhtml

<ui:composition 
    xmlns="http://www.w3.org/1999/xhtml"
    xmlns:f="http://java.sun.com/jsf/core"
    xmlns:h="http://java.sun.com/jsf/html"
    xmlns:ui="http://java.sun.com/jsf/facelets"
    xmlns:p="http://xmlns.jcp.org/jsf/passthrough"
    xmlns:pf="http://primefaces.org/ui">

    <h3>This is the first block</h3>
    <h:panelGrid columns="3" style="margin-bottom:10px" cellpadding="5">

        <pf:outputLabel for="firstName" value="Nombre:" />
        <pf:inputText id="firstName" value="#{bean.firstName}" />
        <h:message id="firstNameMessage" for="firstName" />

    </h:panelGrid>
</ui:composition>

Page1Bean.java

package com.views.prototype;

import java.util.ArrayList;
import java.util.List;
import javax.faces.bean.ManagedBean;
import javax.faces.context.FacesContext;

@ManagedBean
public class Page1Bean {

    private List<String> blockNames;

    private Block1Bean myBean;

    public Page1Bean() {
        blockNames = new ArrayList<String>();

        blockNames.add("block2");
        blockNames.add("block1");

        myBean = new Block1Bean();
    }

    public void ajaxSubmit() {
    }

    @SuppressWarnings("unchecked")
    public static <T> T findBean(String beanName) {
        FacesContext context = FacesContext.getCurrentInstance();
        return (T) context.getApplication().evaluateExpressionGet(context, "#{" + beanName + "}", Object.class);
    }

    public List<String> getBlockNames() {
        return blockNames;
    }

    public void setBlockNames(List<String> blockNames) {
        this.blockNames = blockNames;
    }

    public Block1Bean getMyBean() {
        return myBean;
    }

    public void setMyBean(Block1Bean myBean) {
        this.myBean = myBean;
    }
}

Block1Bean.java

package com.views.prototype;

import javax.faces.bean.ManagedBean;

@ManagedBean
public class Block1Bean {
    private String firstName;

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    @Override
    public String toString() {
        return "Block1Bean [firstName=" + firstName + "]";
    }   
}

页面呈现正常，但是当我点击提交时，我得到：

value="#{bean.firstName}"：目标不可达，标识符“bean”解析为空

据我所知，我使用的语法与这些示例的解决方案相同：

Reusing the same page multiple times

Passing the backing bean as a parameter to a Facelet include

关于我哪里出错了有什么想法吗？

Answer 1

问题原来是 JSTL 和 JSF 之间的冲突，正如几个线程所指出的：

JSTL c:choose c:when not working in a JSF page

Specify conditional rendering of element inside <ui:repeat>? The <c:if> does not seem to work

所以我重写了循环不使用 JSTL，它摆脱了原始问题中的直接问题：

        <ui:repeat var="blockName" value="#{page1Bean.blockNames}" varStatus="status">
            <ui:fragment rendered="#{blockName == 'block1'}">
                <ui:include src="#{page1Bean.theBlockName}" >
                    <ui:param name="bean" value="#{page1Bean.myBean}"/>
                </ui:include>
            </ui:fragment>

            <ui:fragment rendered="#{blockName != 'block1' }">
                <ui:include src="block2.xhtml" />
            </ui:fragment>

        </ui:repeat>

（这在功能上不等同于损坏的预期用途，但关键是它不使用 JSTL）。

Answer 2

这可能是因为您将请求范围的 bean 传递到其他页面。一旦请求完成，bean 就不再存在。尝试对您的 bean 使用更大的范围，例如视图。它应该可以正常工作。

@ManagedBean
@ViewScoped
public class Block1Bean {

}

否则，您将不得不使用 keepAlive 等功能来扩展请求范围。