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java - JSF2 - 为什么呈现响应不重新呈现组件设置？

转载 作者：行者123 更新时间：2023-11-30 06:37:51 25 4
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我遇到了以下问题:

在我的 View 恢复后，字段验证导致 JSF 跳到渲染响应阶段(因为必填字段为空)。但是即使呈现当前值(空字符串)以向用户显示他/她没有填写任何内容，也不会执行以下语句:

 <c:if test="#{empty cc.attrs.fieldValue}">
     <f:attribute name="style" value="background-color: yellow;"/>
 </c:if>

这是错误还是功能？请帮忙。

完整的测试示例(Netbeans 6.8 项目)在这里:http://www.221b.cz/so/JSFTester.zip

来自教程:“如果请求是回发，并且在应用请求值阶段、过程验证阶段或更新模型值阶段遇到错误，则在呈现响应阶段呈现原始页面”(http://java.sun.com/javaee/5/docs/tutorial/doc/bnaqq.html)

这是否意味着如果 View 在“恢复 View ”阶段恢复，然后任何应用请求/验证/更新模型阶段失败并跳到“渲染响应”，即渲染响应仅传递恢复的 View 而不对客户端进行任何更改？

托管 Bean (TesterBean.java):

package cz.test;
import javax.faces.bean.ManagedBean;
import javax.faces.bean.RequestScoped;

@ManagedBean
@RequestScoped
public class TesterBean {

// Simple DataStore (in real world EJB)
private static String storedSomeValue = null;

private String someValue;

public TesterBean() {
}

public String storeValue() {
    storedSomeValue = someValue;
    return "index";
}

public String eraseValue() {
    storedSomeValue = null;
    return "index";
}

public String getSomeValue() {
    someValue = storedSomeValue;
    return someValue;
}

public void setSomeValue(String someValue) {
    this.someValue = someValue;
}    

}

复合组件(field-component.xhtml):

<?xml version='1.0' encoding='ISO-8859-1' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
  xmlns:h="http://java.sun.com/jsf/html"
  xmlns:f="http://java.sun.com/jsf/core"
  xmlns:composite="http://java.sun.com/jsf/composite"
  xmlns:c="http://java.sun.com/jsp/jstl/core">

<!-- INTERFACE -->
<composite:interface>
    <composite:attribute name="currentBehaviour" type="java.lang.String" required="true"/>
    <composite:attribute name="fieldValue" required="true"/>
</composite:interface>

<!-- IMPLEMENTATION -->
<composite:implementation>
    <h:panelGrid columns="3">
        <c:choose>
            <c:when test="#{cc.attrs.currentBehaviour == 'READONLY'}" >
                <h:outputText id="fieldValue" value="#{cc.attrs.fieldValue}">
                </h:outputText>
            </c:when>
            <c:when test="#{cc.attrs.currentBehaviour == 'MANDATORY'}" >
                <h:inputText id="fieldValue" value="#{cc.attrs.fieldValue}" required="true">
                    <f:attribute name="requiredMessage" value="Field is mandatory"/>
                    <c:if test="#{empty cc.attrs.fieldValue}">
                        <f:attribute name="style" value="background-color: yellow;"/>
                    </c:if>
                </h:inputText>&nbsp;*
            </c:when>
            <c:when test="#{cc.attrs.currentBehaviour == 'OPTIONAL'}" >                    
                <h:inputText id="fieldValue" value="#{cc.attrs.fieldValue}">                        
                </h:inputText>                    
            </c:when>
        </c:choose>
        <h:message for="fieldValue" style="color:red;" />
    </h:panelGrid>
</composite:implementation>

页面(index.xhtml):

<?xml version='1.0' encoding='UTF-8' ?>
 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
  <html xmlns="http://www.w3.org/1999/xhtml"
   xmlns:h="http://java.sun.com/jsf/html"      
   xmlns:ez="http://java.sun.com/jsf/composite/components">

<h:head>
    <title>Testing page</title>
</h:head>
<h:body>
    <h:form>                        
        <h:outputText value="Some value:"/>
        <ez:field-component currentBehaviour="MANDATORY" fieldValue="#{testerBean.someValue}"/>           
        <h:commandButton value="Store" action="#{testerBean.storeValue}"/>
        <h:commandButton value="Erase" action="#{testerBean.eraseValue}" immediate="true"/>
    </h:form>

    <br/><br/>
    <b>Why is field's background color not set to yellow?</b>
    <ol>
        <li>NOTICE: Field has yellow background color (mandatory field with no value)</li>
        <li>Fill in any value (eg. "Hello") and press Store</li>
        <li>NOTICE: Yellow background disappeared (as mandatory field has value)</li>
        <li>Clear text in the field and press Store</li>
        <li><b>QUESTION: Why is field's background color not set to yellow?</b></li>
        <li>Press Erase</li>
        <li>NOTICE: Field has yellow background color (mandatory field with no value)</li>
    </ol>
</h:body>

编辑，按照 Brian 的建议 (field-component.xhtml) 

<?xml version='1.0' encoding='ISO-8859-1' ?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
  xmlns:h="http://java.sun.com/jsf/html"
  xmlns:f="http://java.sun.com/jsf/core"
  xmlns:composite="http://java.sun.com/jsf/composite">

<!-- INTERFACE -->
<composite:interface>
    <composite:attribute name="currentBehaviour" type="java.lang.String" required="true"/>
    <composite:attribute name="fieldValue" required="true"/>
</composite:interface>

<!-- IMPLEMENTATION -->
<composite:implementation>
    <h:panelGrid columns="3">
        <h:outputText rendered="#{cc.attrs.currentBehaviour == 'READONLY'}" id="fieldValue1" value="#{cc.attrs.fieldValue}" />

        <h:inputText rendered="#{cc.attrs.currentBehaviour == 'MANDATORY'}" id="fieldValue2" title="#{cc.attrs.fieldValue}" value="#{cc.attrs.fieldValue}" required="true" style="#{empty cc.attrs.fieldValue ? 'background-color: yellow;' : ''}">
            <f:attribute name="requiredMessage" value="Field is mandatory"/>
        </h:inputText>&nbsp;*

        <h:inputText rendered="#{cc.attrs.currentBehaviour == 'OPTIONAL'}" id="fieldValue3" value="#{cc.attrs.fieldValue}"/>

        <h:message for="fieldValue" style="color:red;" />
    </h:panelGrid>
</composite:implementation>

但即使我摆脱了 JSTL 仍然无法正常工作:-( 似乎只有 value 属性使用来自 h:inputText 中的 http 请求的新值进行了更新，但其余属性没有在 Render Response 阶段重新评估。

最佳答案

<c:choose>和 <c:when>您使用的标签是 JSTL 标签，而不是 JSF 标签。这意味着它们是在构建时评估的，而不是在渲染时。当您回发时，组件树不会被重建，而是被重新渲染，并且 <c:标签不会被重新评估。

使用 <h:panelGroup rendered="#{}"> 再次尝试您的示例标签而不是 <c:标签。

有关详细信息，请参阅此文章: http://drewdev.blogspot.com/2008/03/build-time-vs-render-time.html

It is very important to remember that you cannot have components "re-appear" on post back of a JSF form. This is because a JSF component tree should never be altered between having its state saved and when its state is restored. This is very important, so let me say again, a JSF component tree should never be altered between having its state saved and when its state is restored.

关于java - JSF2 - 为什么呈现响应不重新呈现组件设置？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/2995521/

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