PrimeFaces 文件下载不起作用

Question

我无法让 primeFaces <p:filedownload 工作。虽然我使用自定义下载 bean 成功下载了文件。似乎问题与primefaces文件下载ActionListener有关，但我不知道如何。有人有线索吗？谢谢。

这是我的豆子：

@ManagedBean(name="fileDownloadBean")
@SessionScoped
public class FileDownloadBean implements Serializable {

    private StreamedContent file;

    public StreamedContent getFile() {
        return file;
    }

    public void setFile(StreamedContent file) {
        this.file = file;
    }

    /** Creates a new instance of FileDownloadBean */
    public FileDownloadBean() {
        InputStream stream = this.getClass().getResourceAsStream("sessionlog.csv");
        file = new DefaultStreamedContent(stream, "application/csv", "sessionlog.csv");

    }
}

这是我的视图代码：

<?xml version='1.0' encoding='UTF-8' ?>
<!DOCTYPE composition PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<ui:composition xmlns="http://www.w3.org/1999/xhtml"
                xmlns:ui="http://java.sun.com/jsf/facelets"
                xmlns:h="http://java.sun.com/jsf/html"
                xmlns:p="http://primefaces.prime.com.tr/ui" 
                xmlns:f="http://java.sun.com/jsf/core"
                xmlns:o="http://openfaces.org/"
                template="./../template.xhtml">

    <ui:define name="title">
        #{bundle.Log}
    </ui:define>

    <ui:define name="body">
        <h:form>
            <p:separator style="height: 10px;margin-bottom: 10px;margin-top: 0px;"/>
            <p:commandButton value="#{bundle.Log}" image="ui-icon ui-icon-link" ajax="false" disabled="false">
                <p:fileDownload value="#{fileDownloadBean.file}" />
            </p:commandButton>
</ui:composition>

我收到 500 错误：NullPointerException：

HTTP Status 500 -

type Exception report

message

descriptionThe server encountered an internal error () that prevented it from fulfilling this request.

exception

javax.servlet.ServletException
root cause

java.lang.NullPointerException
note The full stack traces of the exception and its root causes are available in the GlassFish Server Open Source Edition 3.1 logs.

GlassFish Server Open Source Edition 3.1

日志：

WARNING: StandardWrapperValve[Faces Servlet]: PWC1406: Servlet.service() for servlet Faces Servlet threw exception
java.lang.NullPointerException
    at org.primefaces.component.filedownload.FileDownloadActionListener.processAction(FileDownloadActionListener.java:59)
    at javax.faces.event.ActionEvent.processListener(ActionEvent.java:88)
    at javax.faces.component.UIComponentBase.broadcast(UIComponentBase.java:769)
    at javax.faces.component.UICommand.broadcast(UICommand.java:300)
    at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:794)
    at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1259)
    at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:409)
    at org.apache.catalina.core.StandardWrapper.service(StandardWrapper.java:1534)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:281)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:175)
    at org.apache.catalina.core.StandardPipeline.doInvoke(StandardPipeline.java:655)
    at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:595)
    at com.sun.enterprise.web.WebPipeline.invoke(WebPipeline.java:98)
    at com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:91)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:162)
    at org.apache.catalina.connector.CoyoteAdapter.doService(CoyoteAdapter.java:326)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:227)
    at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:170)
    at com.sun.grizzly.http.ProcessorTask.invokeAdapter(ProcessorTask.java:822)
    at com.sun.grizzly.http.ProcessorTask.doProcess(ProcessorTask.java:719)
    at com.sun.grizzly.http.ProcessorTask.process(ProcessorTask.java:1013)
    at com.sun.grizzly.http.DefaultProtocolFilter.execute(DefaultProtocolFilter.java:225)
    at com.sun.grizzly.DefaultProtocolChain.executeProtocolFilter(DefaultProtocolChain.java:137)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:104)
    at com.sun.grizzly.DefaultProtocolChain.execute(DefaultProtocolChain.java:90)
    at com.sun.grizzly.http.HttpProtocolChain.execute(HttpProtocolChain.java:79)
    at com.sun.grizzly.ProtocolChainContextTask.doCall(ProtocolChainContextTask.java:54)
    at com.sun.grizzly.SelectionKeyContextTask.call(SelectionKeyContextTask.java:59)
    at com.sun.grizzly.ContextTask.run(ContextTask.java:71)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:532)
    at com.sun.grizzly.util.AbstractThreadPool$Worker.run(AbstractThreadPool.java:513)
    at java.lang.Thread.run(Thread.java:662)

Answer 1

InputStream stream = this.getClass().getResourceAsStream("sessionlog.csv");

您找到 CSV 文件的方式预计它与当前类 FileDownloadBean 位于相同的包中。

如果它实际上位于包根目录中，那么您应该使用：

InputStream stream = this.getClass().getResourceAsStream("/sessionlog.csv");

或者如果它实际上位于不同的包中，例如com.example，那么您应该使用：

InputStream stream = this.getClass().getResourceAsStream("/com/example/sessionlog.csv");

或者，如果它实际上位于公共 web 内容的根目录中（/WEB-INF 文件夹也在所有其他 web 文件中），那么您应该使用：

InputStream stream = externalContext.getResourceAsStream("/sessionlog.csv");

（顺便说一下，它也适用于 WAR 类而不是 this.getClass()）

Answer 2

我正在修改我的 InputStream 代码

InputStream stream = this.getClass().getResourceAsStream("sessionlog.csv");

改变

InputStream stream = new FileInputStream(new File("URL"))

这是解决方案。

Answer 3

您确定已成功将 CSV 文件作为资源从类加载吗？看起来 InputStream 可能为空。

Answer 4

我的fileuplaad.xhtml如下图

  <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:ui="http://java.sun.com/jsf/facelets"
    xmlns:p="http://primefaces.org/ui">


    <h:form id="downloadFileForm">
            <p:commandButton id="downloadLink" value="Download"                                                                             ajax="false"
                                                onclick="PrimeFaces.monitorDownload(start, stop)"
                                                icon="ui-icon-arrowthichk-s">
                                                <p:fileDownload value="#{fileDownloadController.file}" />
                                            </p:commandButton>


        </h:form>
    </html>

Here is my bean:
@ManagedBean(name="fileDownloadController")
public class FileDownloadController implements Serializable {


    private static final long serialVersionUID = 1L;

    private StreamedContent file;  


    public FileDownloadController() {          
        InputStream stream = ((ServletContext)FacesContext.getCurrentInstance().getExternalContext().getContext()).getResourceAsStream("/download/FileName.csv");  
        file = new DefaultStreamedContent(stream, "download/csv", "FileName.csv");  
    }  

    public StreamedContent getFile() {  
        return file;  
    }    
}