Question

我正在尝试将标签云组件添加到我的jsf页面，但它会抛出空指针异常在添加此组件之前，页面正常呈现。我使用了showcase的确切代码，并将managedBean添加到了faces-config。我正在使用eclipse kepler，glassfish 4和primefaces 4
这是我的代码片段

   <!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:f="http://java.sun.com/jsf/core"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:p="http://primefaces.org/ui">
    <f:view contentType="text/html">
<h:head>
    <meta></meta>
    <link rel="stylesheet" type="text/css" href="css/styles.css" />
     </h:head>
<h:body>
     <p:tagCloud model="#{tagCloudBean.model}">  
    <p:ajax event="select" update="msg" listener="#{tagCloudBean.onSelect}" />  
</p:tagCloud> 
                        <p:inputText size="56"></p:inputText>
                        <h:panelGrid columns="2" style="margin-top:10px">
                            <p:commandButton id="submitButton" value="Submit"
                                icon="ui-icon-disk" />
                            <p:commandButton id="clearButton" type="button" value="Clear"
                                onclick="PF('editor').clear()" icon="ui-icon-close" />
                        </h:panelGrid>

这就是日志

      2013-11-22T16:11:03.284+0100|Grave: Error Rendering View[/forum.xhtml]
       java.lang.NullPointerException
   at org.primefaces.component.tagcloud.TagCloudRenderer.encodeMarkup(TagCloudRenderer.java:59)
   at org.primefaces.component.tagcloud.TagCloudRenderer.encodeEnd(TagCloudRenderer.java:38)
   at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:924)
   at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1863)
   at javax.faces.render.Renderer.encodeChildren(Renderer.java:176)
   at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:894)
   at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:304)
at com.sun.faces.renderkit.html_basic.GridRenderer.renderRow(GridRenderer.java:185)
at com.sun.faces.renderkit.html_basic.GridRenderer.encodeChildren(GridRenderer.java:129)
at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:894)
at org.primefaces.renderkit.CoreRenderer.renderChild(CoreRenderer.java:70)
at org.primefaces.renderkit.CoreRenderer.renderChildren(CoreRenderer.java:57)
at org.primefaces.component.panel.PanelRenderer.encodeContent(PanelRenderer.java:204)
at org.primefaces.component.panel.PanelRenderer.encodeMarkup(PanelRenderer.java:121)
at org.primefaces.component.panel.PanelRenderer.encodeEnd(PanelRenderer.java:58)
at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:924)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1863)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1859)
at org.primefaces.component.tabview.TabViewRenderer.encodeTabContent(TabViewRenderer.java:304)
at org.primefaces.component.tabview.TabViewRenderer.encodeContents(TabViewRenderer.java:262)
at org.primefaces.component.tabview.TabViewRenderer.encodeMarkup(TabViewRenderer.java:133)
at org.primefaces.component.tabview.TabViewRenderer.encodeEnd(TabViewRenderer.java:72)
at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:924)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1863)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1859)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1859)
at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:443)
at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:131)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:120)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:219)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:647)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:318)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:357)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:260)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:188)
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:191)
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:168)
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:189)
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:288)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:206)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:136)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:114)
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:838)
at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:113)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:115)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:55)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:135)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:564)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:544)
at java.lang.Thread.run(Thread.java:724)

    2013-11-22T16:11:03.291+0100|Avertissement: StandardWrapperValve[Faces Servlet]:     Servlet.service() for servlet Faces Servlet threw exception
    java.lang.NullPointerException
at org.primefaces.component.tagcloud.TagCloudRenderer.encodeMarkup(TagCloudRenderer.java:59)
at org.primefaces.component.tagcloud.TagCloudRenderer.encodeEnd(TagCloudRenderer.java:38)
at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:924)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1863)
at javax.faces.render.Renderer.encodeChildren(Renderer.java:176)
at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:894)
at com.sun.faces.renderkit.html_basic.HtmlBasicRenderer.encodeRecursive(HtmlBasicRenderer.java:304)
at com.sun.faces.renderkit.html_basic.GridRenderer.renderRow(GridRenderer.java:185)
at com.sun.faces.renderkit.html_basic.GridRenderer.encodeChildren(GridRenderer.java:129)
at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:894)
at org.primefaces.renderkit.CoreRenderer.renderChild(CoreRenderer.java:70)
at org.primefaces.renderkit.CoreRenderer.renderChildren(CoreRenderer.java:57)
at org.primefaces.component.panel.PanelRenderer.encodeContent(PanelRenderer.java:204)
at org.primefaces.component.panel.PanelRenderer.encodeMarkup(PanelRenderer.java:121)
at org.primefaces.component.panel.PanelRenderer.encodeEnd(PanelRenderer.java:58)
at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:924)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1863)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1859)
at org.primefaces.component.tabview.TabViewRenderer.encodeTabContent(TabViewRenderer.java:304)
at org.primefaces.component.tabview.TabViewRenderer.encodeContents(TabViewRenderer.java:262)
at org.primefaces.component.tabview.TabViewRenderer.encodeMarkup(TabViewRenderer.java:133)
at org.primefaces.component.tabview.TabViewRenderer.encodeEnd(TabViewRenderer.java:72)
at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:924)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1863)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1859)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1859)
at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:443)
at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:131)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:120)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:219)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:647)
at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1682)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:318)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:734)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:673)
at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:174)
at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:357)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:260)
at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:188)
at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:191)
at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:168)
at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:189)
at org.glassfish.grizzly.filterchain.ExecutorResolver$9.execute(ExecutorResolver.java:119)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:288)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:206)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:136)
at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:114)
at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:838)
at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:113)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:115)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access$100(WorkerThreadIOStrategy.java:55)
at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:135)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:564)
at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:544)
at java.lang.Thread.run(Thread.java:724)

Answer 1

第一行是什么？

java.lang.NullPointerException
    at org.primefaces.component.tagcloud.TagCloudRenderer.encodeMarkup(TagCloudRenderer.java:59)

好的，让我们看一下source code of TagCloudRenderer的第59行：

59        for(TagCloudItem item : model.getTags()) {

好吧，看似model定义的<p:tagCloud model="#{tagCloudBean.model}"> null或getTags()方法返回null。

从逻辑上讲，这又可能有以下原因：

#{tagCloudBean}不存在，因此null。
#{tagCloudBean.model}返回null。
#{tagCloudBean.model.tags}返回null。

正如您所指出的那样，showcase example包含了正确的模型，但缺少bean管理注释，我认为它是由＃1引起的。

将其添加到faces-config.xml是不必要的，您很可能做错了，例如使用托管bean名称TagCloudBean而不是tagCloudBean。使其成为托管bean，通常的JSF 2.x方式应该解决#{tagCloudBean}为null的问题。它默认为正确的托管bean名称。

@ManagedBean
@RequestScoped
public class TagCloudBean {}

Primefaces Tag Cloud抛出空指针异常

1 个答案: