JSF未显示第一行，第一列数据

StackOverflow https://stackoverflow.com/questions/1917923

  •  20-09-2019
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题

我有一个非常简单的页面显示罐头数据。我从数据库的数据中遇到了这个问题，因此我做了这个简单的示例，但仍然存在问题。当此页面首次导航到会话时，第一行中的第一列没有显示数据。

我是否更改请求或会话的范围都没关系，如果我使用Firefox或IE，也没有区别。我所知道的是，如果我重新加载页面或导航并回来，它将突然显示我的数据 - 直到我关闭该浏览器的所有实例并加载一个新的实例。然后，在我重新加载页面之前，它不会显示我的数据。

问题是，为什么我心爱的第一本书的第一名永远不会出现，直到我重新加载页面（“操作系统概念”不显示，而是“ Silberschatz”）？

以下是相关代码。

homepage.java：

public class HomePage {

    private Book[] books;

    public HomePage() {
        books = new Book[3];
        books[0] = new Book("Operating System Concepts", "Silberschatz");
        books[1] = new Book("Learning Sql", "Beaulieu");
        books[2] = new Book("Effective Java", "Bloch");
    }

    public Book[] getBooks() {
        return books;
    }
    public void setBooks(Book[] books) {
        this.books = books;
    }
}

book.java

public class Book {

    private String title;
    private String author;

    public Book() {}

    public Book(String title, String author) {
        this.title = title;
        this.author = author;
    }


    public String getTitle() {
        return title;
    }
    public void setTitle(String title) {
        this.title = title;
    }

    public String getAuthor() {
        return author;
    }
    public void setAuthor(String author) {
        this.author = author;
    }
}

home.jsp：

<html>
  <%@ taglib uri="http://java.sun.com/jsf/core" prefix="f" %>
  <%@ taglib uri="http://java.sun.com/jsf/html" prefix="h" %>

  <link href="../css/styles.css" rel="stylesheet" type="text/css" />
  <f:loadBundle basename="omitted.for.anonymity.bundle.home" var="msgs"/>

  <f:view>
    <body>
      <h:form>
        <h:panelGrid columns="2" columnClasses="sideControlColumn,contentColumn">
          <f:facet name="header">
            <f:subview id="header">
              <jsp:include page="header.jsp" />
            </f:subview>
          </f:facet>

          <f:subview id="sideControl" >
            <jsp:include page="sideControl.jsp" />
          </f:subview>

          <h:dataTable value="#{homePage.books}"
                var="book"
                styleClass="homeTable"
                rowClasses="evenColumn,oddColumn"
                >

            <h:column>
              <f:facet name="header">
                <h:outputText value="#{msgs.columnHeader1}"/>
              </f:facet>

              <h:outputText value="#{book.title}" />
            </h:column>

            <h:column>
              <f:facet name="header">
                <h:outputText value="#{msgs.columnHeader2}"/>
              </f:facet>

              <h:outputText value="#{book.author}" />
            </h:column>

          </h:dataTable>

        </h:panelGrid>
      </h:form>
    </body>
     </f:view>
</html>

faces-config.xml：

<?xml version="1.0"?>
<!DOCTYPE faces-config PUBLIC
    "-//Sun Microsystems, Inc.//DTD JavaServer Faces Config 1.1//EN"
    "http://java.sun.com/dtd/web-facesconfig_1_1.dtd">

<faces-config>

    <navigation-rule>
    <from-view-id>/pages/login.jsp</from-view-id>
        <navigation-case>
            <from-outcome>login</from-outcome>
            <to-view-id>/pages/home.jsp</to-view-id>
        </navigation-case>
    </navigation-rule>

    <navigation-rule>
    <from-view-id>/pages/home.jsp</from-view-id>
        <navigation-case>
            <from-outcome>searchForBooks</from-outcome>
            <to-view-id>/pages/searchCriteria.jsp</to-view-id>
        </navigation-case>
    </navigation-rule>

    <navigation-rule>
    <from-view-id>/pages/searchCriteria.jsp</from-view-id>
        <navigation-case>
            <from-outcome>searchForBooks</from-outcome>
            <to-view-id>/pages/searchCriteria.jsp</to-view-id>
        </navigation-case>
    </navigation-rule>

    <navigation-rule>
    <from-view-id>/pages/searchResults.jsp</from-view-id>
        <navigation-case>
            <from-outcome>searchForBooks</from-outcome>
            <to-view-id>/pages/searchCriteria.jsp</to-view-id>
        </navigation-case>
    </navigation-rule>

    <navigation-rule>
    <from-view-id>/pages/searchCriteria.jsp</from-view-id>
        <navigation-case>
            <from-outcome>search</from-outcome>
            <to-view-id>/pages/searchResults.jsp</to-view-id>
        </navigation-case>
    </navigation-rule>


    <managed-bean>
        <managed-bean-name>book</managed-bean-name>
        <managed-bean-class>omitted.for.anonymity.beans.Book</managed-bean-class>
        <managed-bean-scope>session</managed-bean-scope>
    </managed-bean>
    <managed-bean>
        <managed-bean-name>homePage</managed-bean-name>
        <managed-bean-class>omitted.for.anonymity.beans.page.HomePage</managed-bean-class>
        <managed-bean-scope>session</managed-bean-scope>
    </managed-bean>
    <managed-bean>
        <managed-bean-name>searchCriteriaPage</managed-bean-name>
        <managed-bean-class>omitted.for.anonymity.beans.page.SearchCriteriaPage</managed-bean-class>
        <managed-bean-scope>session</managed-bean-scope>
    </managed-bean>
    <managed-bean>
        <managed-bean-name>searchResultsPage</managed-bean-name>
        <managed-bean-class>omitted.for.anonymity.beans.page.SearchResultsPage</managed-bean-class>
        <managed-bean-scope>request</managed-bean-scope>
    </managed-bean>

</faces-config>
有帮助吗？

解决方案

设置一个 book 请求范围变量：

<h:dataTable value="#{homePage.books}"
    var="book"
    styleClass="homeTable"
    rowClasses="evenColumn,oddColumn">

托管bean设置一个 book 会话范围变量：

<managed-bean>
    <managed-bean-name>book</managed-bean-name>
    <managed-bean-class>omitted.for.anonymity.beans.Book</managed-bean-class>
    <managed-bean-scope>session</managed-bean-scope>
</managed-bean>

只是猜测，但我想知道出于某种原因，表达式语言是否在此处解决session bean。它不应该 - ScopEdattributeElresolver “搜索带有给定名称的属性的页面，请求，会话和应用程序范围并将其返回，或者如果没有当前名称的属性，则null。” 但是表达式语言实现中没有一个错误。尝试更改名称 var 属性以避免使用或将其明确解决到范围 #{requestScope.book.title}.

<!DOCTYPE faces-config PUBLIC
  "-//Sun Microsystems, Inc.//DTD JavaServer Faces Config 1.1//EN"
  "http://java.sun.com/dtd/web-facesconfig_1_1.dtd">

我从您的Doctype注意到您正在使用JSF 1.1。如果可以的话，我建议至少升级至至少1.2（最好是2.0）。

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