org.primefaces.component.filedownload.FileDownloadActionListener.processAction上的java.lang.NullPointerException [英] java.lang.NullPointerException at org.primefaces.component.filedownload.FileDownloadActionListener.processAction

问题描述

我正在从事一个JSF / PrimeFaces项目，我从数据库生成一些文件，并将它们放在我的项目的web / resources文件夹中。我使用ap：datable将文件名动态地加载到一个网页。数据表启用了单个模式。我想要的是根据用户选择使文件可以下载。当选择一个文件并按下下载按钮抛出异常时;

以下是我使用的代码：

JSF页面

 < div id =content> 
< h：form id =resultForm> 
< center> 
< p：panel id =filesstyle =width：80％> 
< p：dataTable id =resultDTvar =filevalue =＃{gen.outFileNames}
 selection =＃{downloader.selectedFileName}selectionMode =singlerowKey = ＃{文件} > 
< f：facet name =header> 
生成的文件
< / f：facet> 
< p：column headerText =文件名> 
< h：outputText value =＃{file}/> 
< / p：column> 
< f：facet name =footer> 
< p：commandButton value =下载ajax =falseicon =ui-icon-arrowthick-1-s> 
< p：fileDownload value =＃{downloader.file}/> 
< / p：commandButton> 
< / f：facet> 
< / p：dataTable> 
< / p：panel> 
< / center> 
< / h：form> 
< / div> 
  

下载控制器

 code> @ManagedBean（name =downloader）
 @ViewScoped 
 public class FilesDownloadController implements Serializable {
 
 private String selectedFileName; 
 
 public StreamedContent getFile（）{
 if（selectedFileName == null）{
 FacesContext.getCurrentInstance（）。addMessage（null，new FacesMessage（FacesMessage.SEVERITY_WARN，
下载警告，请点击文件并点击下载按钮。））; 
返回null; 
} 
 System.out.println（下载1：selectedFileName =+ selectedFileName）; 
 System.out.println（下载2）; 
 
 System.out.println（下载3）; 
 InputStream stream = this.getClass（）。getResourceAsStream（selectedFileName）; 
 System.out.println（下载4）; 
 StreamedContent file = new DefaultStreamedContent（stream，（（ServletContext）FacesContext.getCurrentInstance（）。getExternalContext（）。getContext（））。getMimeType（selectedFileName），
 selectedFileName.split（/）[selectedFileName .split（/）。length  -  1]）; 
 System.out.println（Download 5 =+ selectedFileName.split（/）[selectedFileName.split（/）。length  -  1]）; 
 System.out.println（file！= null？文件内容OK+ file.getContentType（）++ file.getName（）：文件内容NOK）; 
返回文件; 
} 
 
 public String getSelectedFileName（）{
 return selectedFileName; 
} 
 
 public void setSelectedFileName（String selectedFileName）{
 this.selectedFileName = selectedFileName; 
 System.out.println（Selected File changed：+ this.selectedFileName）; 
} 
} 
  

生成器bean

  @ManagedBean（name =gen）
 @SessionScoped 
 public class GeneratorController implements Serializable {
 
 private List< ;字符串> outFileNames; 
 
 public GeneratorController（）{
 outFileNames = new ArrayList< String>（）; 
 outFileNames.add（/ resources / images / optimus.jpg）; 
 outFileNames.add（/ resources / images / optimus_1.jpg）; 
 outFileNames.add（/ resources / images / optimus_2.jpg）; 
 outFileNames.add（/ resources / images / optimus_3.jpg）; 
} 
 
 public List< String> getOutFileNames（）{
 return outFileNames; 
} 
 
 public void setOutFileNames（List< String> outFileNames）{
 this.outFileNames = outFileNames; 
} 
} 
  

抛出异常

 信息：所选文件已更改：/resources/images/optimus_1.jpg 
信息：下载1：selectedFileName = /resources/images/optimus_1.jpg 
信息：下载2 
信息：下载3 
信息：下载4 
信息：下载5 = optimus_1.jpg 
信息：文件内容OK image / jpeg optimus_1.jpg 
 FATAL：JSF1073：javax.faces.FacesExceptioninterceptédurant le traitement de INVOKE_APPLICATION 5：UIComponent-ClientId =，Message = null 
 FATAL：没有关联的消息
 javax.faces.FacesException 
在com.sun.faces.lifecycle.InvokeApplicationPhase.execute（InvokeApplicationPhase.java:89）
在com.sun.faces.lifecycle.Phase.doPhase（Phase.java:101）
在com.sun .faces.lifecycle.LifecycleImpl.execute（LifecycleImpl.java:198）
在javax.faces.webapp.FacesSe rvlet.service（FacesServlet.java:646）
在org.apache.catalina.core.StandardWrapper.service（StandardWrapper.java:1682）
在org.apache.catalina.core.StandardWrapperValve.invoke（ StandardWrapperValve.java:318）
在org.apache.catalina.core.StandardContextValve.invoke（StandardContextValve.java:160）
在org.apache.catalina.core.StandardPipeline.doInvoke（StandardPipeline.java： 734）
在org.apache.catalina.core.StandardPipeline.invoke（StandardPipeline.java:673）
在com.sun.enterprise.web.WebPipeline.invoke（WebPipeline.java:99）
在org.apache.catalina.core.StandardHostValve.invoke（StandardHostValve.java:174）
在org.apache.catalina.connector.CoyoteAdapter.doService（CoyoteAdapter.java:415）
在org .apache.catalina.connector.CoyoteAdapter.service（CoyoteAdapter.java:282）
在com.sun.enterprise.v3.services.impl.ContainerMapper $ HttpHandlerCallable.call（ContainerMapper.java:459）
在com.sun.enterprise.v3.services.impl.ContainerMapper.service（ContainerMapper.java:167）
在org.glassfish.grizzly.http.server.HttpHandler.runService（HttpHandler.java:201）
在org.glassfish.grizzly.http.server.HttpHandler.doHandle（HttpHandler.java:175）
在org.glassfish.grizzly.http.server.HttpServerFilter.handleRead（HttpServerFilter.java:235）
在org.glassfish.grizzly.filterchain.ExecutorResolver $ 9.execute（ExecutorResolver.java:119）
在org.glassfish.grizzly.filterchain.DefaultFilterChain.executeFilter（DefaultFilterChain.java:284）
 at org.glassfish.grizzly.filterchain.DefaultFilterChain.executeChainPart（DefaultFilterChain.java:201）
在org.glassfish.grizzly.filterchain.DefaultFilterChain.execute（DefaultFilterChain.java:133）
在org.glassfish。 grizzly.filterchain.DefaultFilterChain.process（DefaultFilterChain.java:112）
在org.glassfish.grizzly.ProcessorExecutor.execute（ProcessorE xecutor.java:77）
在org.glassfish.grizzly.nio.transport.TCPNIOTransport.fireIOEvent（TCPNIOTransport.java:561）
在org.glassfish.grizzly.strategies.AbstractIOStrategy.fireIOEvent（AbstractIOStrategy。 java：112）
在org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.run0（WorkerThreadIOStrategy.java:117）
在org.glassfish.grizzly.strategies.WorkerThreadIOStrategy.access $ 100（WorkerThreadIOStrategy.java:56 ）
在org.glassfish.grizzly.strategies.WorkerThreadIOStrategy $ WorkerThreadRunnable.run（WorkerThreadIOStrategy.java:137）
在org.glassfish.grizzly.threadpool.AbstractThreadPool $ Worker.doWork（AbstractThreadPool.java:565 ）
在org.glassfish.grizzly.threadpool.AbstractThreadPool $ Worker.run（AbstractThreadPool.java:545）
在java.lang.Thread.run（Thread.java:745）
导致通过：java.lang.NullPointerException 
在org.primefaces.component.filedownload.FileDownloadActionListener.processAction（FileDow nloadActionListener.java:81）
在javax.faces.event.ActionEvent.processListener（ActionEvent.java:88）
在javax.faces.component.UIComponentBase.broadcast（UIComponentBase.java:813）
 at javax.faces.component.UICommand.broadcast（UICommand.java:300）
在javax.faces.component.UIData.broadcast（UIData.java:1108）
在javax.faces.component .UIViewRoot.broadcastEvents（UIViewRoot.java:790）
在javax.faces.component.UIViewRoot.processApplication（UIViewRoot.java:1282）
在com.sun.faces.lifecycle.InvokeApplicationPhase.execute（InvokeApplicationPhase .java：81）
 ... 31更多
  

解决方案

我终于有了一种下载文件的方法。图像所在的文件夹不在类路径上，所以

  InputStream stream = this.getClass（）。getResourceAsStream（ selectedFileName）; 
  

返回 null ，发生NPE。所以通过用

webapp上下文用于查找文件，它的工作原理

I am working on a JSF/PrimeFaces project where I am generating some files from a database and placing them in the web/resources folder of my project.I am using a p:datable to load the file names dynamically into a web page. The datatable has a singleMode activated. What I want is to make the files downloadable based on the users choice.when a file is selected and the download button is pushed an exception is thrown;

Here are the codes I used:

JSF page

   <div id="content">
        <h:form id="resultForm">
            <center>
                <p:panel id="files" style="width: 80%">
                    <p:dataTable id="resultDT" var="file" value="#{gen.outFileNames}" 
                                 selection="#{downloader.selectedFileName}" selectionMode="single" rowKey="#{file}">
                        <f:facet name="header">
                            Generated Files
                        </f:facet>
                        <p:column headerText="File names">
                            <h:outputText value="#{file}" />
                        </p:column>
                        <f:facet name="footer">
                            <p:commandButton value="Download" ajax="false" icon="ui-icon-arrowthick-1-s">
                                <p:fileDownload value="#{downloader.file}"/>
                            </p:commandButton>
                        </f:facet>
                    </p:dataTable>
                </p:panel>
            </center>
        </h:form>
    </div>

Download Controller

@ManagedBean(name = "downloader")
@ViewScoped
public class FilesDownloadController implements Serializable {

    private String selectedFileName;

    public StreamedContent getFile() {
        if (selectedFileName == null) {
            FacesContext.getCurrentInstance().addMessage(null, new FacesMessage(FacesMessage.SEVERITY_WARN,
                    "Download warning", "Please click a file and click on the download button."));
            return null;
        }
        System.out.println("Download 1 : selectedFileName = " + selectedFileName);
        System.out.println("Download 2");

        System.out.println("Download 3");
        InputStream stream = this.getClass().getResourceAsStream(selectedFileName);
        System.out.println("Download 4");
        StreamedContent file = new DefaultStreamedContent(stream, ((ServletContext)FacesContext.getCurrentInstance().getExternalContext().getContext()).getMimeType(selectedFileName), 
        selectedFileName.split("/")[selectedFileName.split("/").length - 1]);
        System.out.println("Download 5 = " + selectedFileName.split("/")[selectedFileName.split("/").length - 1]);
        System.out.println(file != null ? "File content OK " + file.getContentType() + " " + file.getName() : "File content NOK");
        return file;
    }

    public String getSelectedFileName() {
        return selectedFileName;
    }

    public void setSelectedFileName(String selectedFileName) {
        this.selectedFileName = selectedFileName;
        System.out.println("Selected File changed: " + this.selectedFileName );
    }
}

Generator bean

@ManagedBean(name = "gen")
@SessionScoped
public class GeneratorController implements Serializable {

private List<String> outFileNames;

public GeneratorController() {
    outFileNames = new ArrayList<String>();
    outFileNames.add("/resources/images/optimus.jpg");
    outFileNames.add("/resources/images/optimus_1.jpg");
    outFileNames.add("/resources/images/optimus_2.jpg");
    outFileNames.add("/resources/images/optimus_3.jpg");
}

public List<String> getOutFileNames() {
    return outFileNames;
}

public void setOutFileNames(List<String> outFileNames) {
    this.outFileNames = outFileNames;
}
}

Exceptions thrown

        Infos:   Selected File changed: /resources/images/optimus_1.jpg
        Infos:   Download 1 : selectedFileName = /resources/images/optimus_1.jpg
        Infos:   Download 2
        Infos:   Download 3
        Infos:   Download 4
        Infos:   Download 5 = optimus_1.jpg
        Infos:   File content OK image/jpeg optimus_1.jpg
        FATAL:   JSF1073 : javax.faces.FacesException intercepté durant le      traitement de INVOKE_APPLICATION 5 : UIComponent-ClientId=, Message=null
        FATAL:   No associated message
javax.faces.FacesException
        at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:89)
        at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
        at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:198)
        at javax.faces.webapp.FacesServlet.service(FacesServlet.java:646)
        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:415)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:282)
        at com.sun.enterprise.v3.services.impl.ContainerMapper$HttpHandlerCallable.call(ContainerMapper.java:459)
        at com.sun.enterprise.v3.services.impl.ContainerMapper.service(ContainerMapper.java:167)
        at org.glassfish.grizzly.http.server.HttpHandler.runService(HttpHandler.java:201)
        at org.glassfish.grizzly.http.server.HttpHandler.doHandle(HttpHandler.java:175)
        at org.glassfish.grizzly.http.server.HttpServerFilter.handleRead(HttpServerFilter.java:235)
        at org.glassfish.grizzly.filterchain.ExecutorResolver$9.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:561)
       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.access$100(WorkerThreadIOStrategy.java:56)
       at org.glassfish.grizzly.strategies.WorkerThreadIOStrategy$WorkerThreadRunnable.run(WorkerThreadIOStrategy.java:137)
       at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.doWork(AbstractThreadPool.java:565)
       at org.glassfish.grizzly.threadpool.AbstractThreadPool$Worker.run(AbstractThreadPool.java:545)
       at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
       at org.primefaces.component.filedownload.FileDownloadActionListener.processAction(FileDownloadActionListener.java:81)
       at javax.faces.event.ActionEvent.processListener(ActionEvent.java:88)
       at javax.faces.component.UIComponentBase.broadcast(UIComponentBase.java:813)
       at javax.faces.component.UICommand.broadcast(UICommand.java:300)
       at javax.faces.component.UIData.broadcast(UIData.java:1108)
       at javax.faces.component.UIViewRoot.broadcastEvents(UIViewRoot.java:790)
       at javax.faces.component.UIViewRoot.processApplication(UIViewRoot.java:1282)
       at com.sun.faces.lifecycle.InvokeApplicationPhase.execute(InvokeApplicationPhase.java:81)
    ... 31 more

解决方案

I finally got a way to download the files. The folder where the images are located is not on the class path, so

InputStream stream = this.getClass().getResourceAsStream(selectedFileName);

returns null and an NPE occurs. So by replacing the code of the Download controller with

InputStream stream = ((ServletContext)FacesContext.getCurrentInstance().getExternalContext().getContext()).getResourceAsStream(selectedFileName);

The webapp context is used for locating the files and it works

这篇关于org.primefaces.component.filedownload.FileDownloadActionListener.processAction上的java.lang.NullPointerException的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！