org.primefaces.component.column.Column 无法转换为 javax.faces.component.ActionSource

Question

总结：我一直在开发一个有点复杂的带有文档列表的 JSF 表单，现在想在该列表的每一行中添加一个按钮，这样您就可以下载文档文件。 Primefaces 对此提供了一个有吸引力的解决方案，所以我逐渐将整个页面转换为使用 primefaces，但现在我只是转换了文档的 table - 这很有效，虽然它看起来很奇怪。我的问题是，当我添加 p:commandButton 时出现异常，我什至不知道它是什么意思 - 据我所知，我正在按照我能够找到的示例进行操作，包括在 primefaces 的展示柜上：

org.primefaces.component.column.Column cannot be cast to javax.faces.component.ActionSource

这是 table 详细信息

<h:form id="doclistform">
    <p:dataTable value="#{documentsController.documentList}" var="doclst"
                 id="doclist">
        <!-- innocent columns -->
        <p:column>
            <f:facet name="header">
                <h:outputText value="Download"/>
            </f:facet>
            <p:fileDownload value="#{doclst.docfile}"/>
        </p:column>
    </p:dataTable>
</h:form>

server.log中的异常：

[2017-11-29T09:27:33.935+0000] [glassfish 5.0] [FATAL] [jsf.context.exception.handler.log] [javax.enterprise.resource.webcontainer.jsf.context] [tid: _ThreadID=31 _ThreadName=http-listener-1(5)] [timeMillis: 1511947653935] [levelValue: 1100] [[
  JSF1073: java.lang.ClassCastException caught during processing of RENDER_RESPONSE 6 : UIComponent-ClientId=, Message=org.primefaces.component.column.Column cannot be cast to javax.faces.component.ActionSource]]

[2017-11-29T09:27:33.936+0000] [glassfish 5.0] [FATAL] [] [javax.enterprise.resource.webcontainer.jsf.context] [tid: _ThreadID=31 _ThreadName=http-listener-1(5)] [timeMillis: 1511947653936] [levelValue: 1100] [[
  org.primefaces.component.column.Column cannot be cast to javax.faces.component.ActionSource
java.lang.ClassCastException: org.primefaces.component.column.Column cannot be cast to javax.faces.component.ActionSource
        at org.primefaces.component.filedownload.FileDownloadTagHandler.apply(FileDownloadTagHandler.java:56)
        at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:96)
        at javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler(DelegatingMetaTagHandler.java:161)
        at com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply(ComponentTagHandlerDelegateImpl.java:203)
        at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:135)
        at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:96)
        at javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler(DelegatingMetaTagHandler.java:161)
        at com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply(ComponentTagHandlerDelegateImpl.java:203)
        at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:135)
        at javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler(DelegatingMetaTagHandler.java:161)
        at com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply(ComponentTagHandlerDelegateImpl.java:203)
        at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:135)
        at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:96)
        at javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler(DelegatingMetaTagHandler.java:161)
        at com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply(ComponentTagHandlerDelegateImpl.java:203)
        at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:135)
        at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:96)
        at javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler(DelegatingMetaTagHandler.java:161)
        at com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply(ComponentTagHandlerDelegateImpl.java:203)
        at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:135)
        at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:96)
        at javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler(DelegatingMetaTagHandler.java:161)
        at com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply(ComponentTagHandlerDelegateImpl.java:203)
        at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:135)
        at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:96)
        at javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler(DelegatingMetaTagHandler.java:161)
        at com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply(ComponentTagHandlerDelegateImpl.java:203)
        at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:135)
        at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:96)
        at javax.faces.view.facelets.DelegatingMetaTagHandler.applyNextHandler(DelegatingMetaTagHandler.java:161)
        at com.sun.faces.facelets.tag.jsf.ComponentTagHandlerDelegateImpl.apply(ComponentTagHandlerDelegateImpl.java:203)
        at javax.faces.view.facelets.DelegatingMetaTagHandler.apply(DelegatingMetaTagHandler.java:135)
        at javax.faces.view.facelets.CompositeFaceletHandler.apply(CompositeFaceletHandler.java:96)
        at com.sun.faces.facelets.compiler.NamespaceHandler.apply(NamespaceHandler.java:94)
        at com.sun.faces.facelets.compiler.EncodingHandler.apply(EncodingHandler.java:88)
        at com.sun.faces.facelets.impl.DefaultFacelet.apply(DefaultFacelet.java:162)
        at com.sun.faces.application.view.FaceletViewHandlingStrategy.buildView(FaceletViewHandlingStrategy.java:381)
        at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:102)
        at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:100)
        at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:223)
        at javax.faces.webapp.FacesServlet.service(FacesServlet.java:671)
        at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1580)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:258)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:160)
        at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:652)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:591)
        at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:99)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:155)
        at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:371)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:238)
        at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:463)
        at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:168)
        at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:206)
        at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:180)
        at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:242)
        at org.glassfish.grizzly.filterchain.ExecutorResolver.execute(ExecutorResolver.java:119)
        at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter(DefaultFilterChain.java:284)
        at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart(DefaultFilterChain.java:201)
        at org.glassfish.grizzly.filterchain.DefaultFilterChain.execute(DefaultFilterChain.java:133)
        at org.glassfish.grizzly.filterchain.DefaultFilterChain.process(DefaultFilterChain.java:112)
        at org.glassfish.grizzly.ProcessorExecutor.execute(ProcessorExecutor.java:77)
        at org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent(TCPNIOTransport.java:539)
        at org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent(AbstractIOStrategy.java:112)
        at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0(WorkerThreadIOStrategy.java:117)
        at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access0(WorkerThreadIOStrategy.java:56)
        at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
        at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:593)
        at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:573)
        at java.lang.Thread.run(Thread.java:745)

Answer 1

如果您查看 PrimeFaces showcase，您会注意到 <p:fileDowload> 嵌入在 <p:commandButton> 标记中：文件下载需要一个操作源（如提到的错误）触发下载。

只需用 p:commandButton 包裹您的 p:fileDownload。

<p:column>
    <f:facet name="header">
        <h:outputText value="Download"/>
    </f:facet>
    <p:commandButton value="Download" ajax="false">
        <p:fileDownload value="#{doclst.docfile}"/>
    </p:commandButton>
</p:column>

处理文件下载时，确保：

the p:commandButton has ajax="false" attribute

the p:fileDownload value is not the File object but a StreamedContent

与下载无关，但您可以使用 p:column 的 headerText 属性来简化代码：

<p:column headerText="Download">
    <p:commandButton value="Download" ajax="false">
        <p:fileDownload value="#{doclst.docfile}"/>
    </p:commandButton>
</p:column>

org.primefaces.component.column.Column 无法转换为 javax.faces.component.ActionSource

org.primefaces.component.column.Column cannot be cast to javax.faces.component.ActionSource

primefaces

jsf-2