不知道如何迭代<c:forEach>中提供的"items"

Question

我在我的应用程序中使用JSF 1.2.我试图遍历一个String数组,这个数组在我的支持bean中定义,如下所示:

private String[] services;

下面是faces-config文件中的托管bean条目:

<managed-bean>     
    <managed-bean-name>registrationBean</managed-bean-name>
    <managed-bean-class>com.bean.RegistrationBean</managed-bean-class>
    <managed-bean-scope>request</managed-bean-scope>        
</managed-bean>

我试图迭代用户选择的服务并将其显示在我的屏幕上.以下是我使用的代码:

<c:forEach items="#{registrationBean.services}" var="service">
    <c:out value="${service}"></c:out>
</c:forEach>

但是我收到了错误:

Don't know how to iterate over supplied "items" in <c:forEach>

请告诉我如何解决这个问题.

编辑

如果我String[]改为List<String>那么我得到这个例外:

java.lang.RuntimeException: wrapped Exception: java.lang.UnsupportedOperationException
com.icesoft.faces.webapp.http.servlet.MainServlet.service(MainServlet.java:156)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
com.icesoft.faces.webapp.xmlhttp.BlockingServlet.service(BlockingServlet.java:56)

下面是Backing Bean初始化:

private List<String> services;
public RegistrationBean() {
    this.services = new ArrayList<String>();
}

faces-config.xml中:

<?xml version='1.0' encoding='UTF-8'?>

<managed-bean>     
    <managed-bean-name>registrationBean</managed-bean-name>
    <managed-bean-class>com.bean.RegistrationBean</managed-bean-class>
    <managed-bean-scope>request</managed-bean-scope>        
</managed-bean>   

<navigation-rule>
    <description>This will navigate to the Success screen.</description>
    <from-view-id>/registration.jspx</from-view-id>
    <navigation-case>
        <from-outcome>success</from-outcome>
        <to-view-id>/success.jspx</to-view-id>
    </navigation-case>
</navigation-rule>

web.xml中:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:web="http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">

<description>
    ICEfaces Address Demo
</description>

<context-param>
    <param-name>javax.faces.STATE_SAVING_METHOD</param-name>
    <param-value>server</param-value>
</context-param>

<context-param>
    <param-name>javax.faces.application.CONFIG_FILES</param-name>
    <param-value>/WEB-INF/faces-config.xml</param-value>
</context-param>

<context-param>
    <param-name>com.sun.faces.validateXml</param-name>
    <param-value>true</param-value>
</context-param>
<context-param>
    <param-name>com.icesoft.faces.synchronousUpdate</param-name>
    <param-value>true</param-value>
</context-param>

<context-param>
  <param-name>javax.faces.DEFAULT_SUFFIX</param-name>
  <param-value>.jspx</param-value>
</context-param>

<listener>
    <listener-class>com.icesoft.faces.util.event.servlet.ContextEventRepeater</listener-class>
</listener>

<!-- Faces Servlet -->
<servlet>
    <servlet-name>Faces Servlet</servlet-name>
    <servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
    <load-on-startup> 1 </load-on-startup>
</servlet>

<servlet>
    <servlet-name>Persistent Faces Servlet</servlet-name>
    <servlet-class>com.icesoft.faces.webapp.xmlhttp.PersistentFacesServlet</servlet-class>
    <load-on-startup> 1 </load-on-startup>
</servlet>

<servlet>
    <servlet-name>Blocking Servlet</servlet-name>
    <servlet-class>com.icesoft.faces.webapp.xmlhttp.BlockingServlet</servlet-class>
    <load-on-startup> 1 </load-on-startup>
</servlet>

<!-- Faces Servlet Mapping -->
<servlet-mapping>
    <servlet-name>Faces Servlet</servlet-name>
    <url-pattern>*.faces</url-pattern>
</servlet-mapping>

<servlet-mapping>
    <servlet-name>Faces Servlet</servlet-name>
    <url-pattern>*.jspx</url-pattern>
</servlet-mapping>

<!-- Persistent Faces Servlet Mapping -->
<servlet-mapping>
    <servlet-name>Persistent Faces Servlet</servlet-name>
    <url-pattern>*.iface</url-pattern>
</servlet-mapping>

<servlet-mapping>
    <servlet-name>Persistent Faces Servlet</servlet-name>
    <url-pattern>/xmlhttp/*</url-pattern>
</servlet-mapping>

<servlet-mapping>
    <servlet-name>Blocking Servlet</servlet-name>
    <url-pattern>/block/*</url-pattern>
</servlet-mapping>

<session-config>
  <session-timeout>30</session-timeout>
</session-config>


<welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>

Answer 1

如果您使用的是JSF 1.2,我无法解释为什么会出现此问题.很可能您的项目或环境混乱了重复或冲突的库.或者faces-config.xml声明符合JSF 1.1而不是JSF 1.2.或者也许ICEfaces以某种方式发挥了作用,但我无法分辨,因为我从未真正使用过该库.

无论如何,当你实际使用JSF 1.1时,我可以特别解释这个问题.在#{}随后不JSP标记在所有支持和<c:forEach items>将产生的正是这种错误.

不知道如何迭代<c:forEach>中提供的"items"

然后,您应该始终${}在JSP标记中使用.但是,${}当它们不在范围中时,它们不会自动创建JSF托管bean.在这种情况下,<c:forEach>将有效地获得一个空集合并且不提供任何内容(但因此不会产生您正面临的错误!).

因此,您需要确保在<c:forEach>输入之前已经自动处理了JSF托管bean .您可以通过使用完整的JSF组件(如<h:panelGroup rendered="#{not empty bean.list}">包装标记或<h:outputText value="#{bean.text}">标记之前)来实现.

例如

<h:someComponent someAttribute="#{registrationBean.something}" />
<c:forEach items="${registrationBean.services}" var="service">
    <c:out value="${service}" />
</c:forEach>

一个完整的JSF 1.x替代方案是使用Tomahawk <t:dataList>而不是JSTL <c:forEach>.

<t:dataList value="#{registrationBean.services}" var="service">
    <h:outputText value="#{service}" />
</t:dataList>