Vaadin 使用PipedInputStream和；PipedOutputStream示例

我刚开始学习Vaadin 8，我的第一个例子是上传按钮。我被困在一个问题中，好几个小时都无法解决这个问题

在这里

我在receiveUpload方法中返回PipedOutputStream

  public OutputStream receiveUpload(String filename, String mimeType) {
  this.fileName = filename;
  this.mimeType = mimeType;
  try {

     pipedOutputStream = new PipedOutputStream();
     pipedInputStream = new PipedInputStream(pipedOutputStream);

    if (filename == null || filename.trim().length() == 0) {
        upload.interruptUpload();
     } else {
     }
  } catch (Exception e) {
     e.printStackTrace();
  }
  return pipedOutputStream;
}

这是receiveUpload方法的代码

  public OutputStream receiveUpload(String filename, String mimeType) {
  this.fileName = filename;
  this.mimeType = mimeType;
  try {

     pipedOutputStream = new PipedOutputStream();
     pipedInputStream = new PipedInputStream(pipedOutputStream);

    if (filename == null || filename.trim().length() == 0) {
        upload.interruptUpload();
     } else {
     }
  } catch (Exception e) {
     e.printStackTrace();
  }
  return pipedOutputStream;
}

在UploadSuccessed方法中，我需要获取pipedinputstream并将另一个方法发送给它以将流加载到数据库中

  public void uploadSucceeded(SucceededEvent event) {
     try { 
        fileUploadOperation.upload(pipedInputStream); --> I need to push all the stream data in one go into a method to generate a file at the business layer
     } catch (Exception e) {
        e.printStackTrace();
     }
  }

当我运行应用程序时，它挂起了很长一段时间，我不知道它在哪里。稍后我会注意到，管道输入和管道输出流都应该在单独的线程中创建，或者至少其中一个在单独的线程中创建，但不知道如何处理它

有什么帮助吗

我正在粘贴完整的课程以获取更多信息

public class WebCommunityView implements Receiver, FailedListener, SucceededListener, StartedListener, FinishedListener {

       private PipedOutputStream pipedOutputStream = null;
       private PipedInputStream pipedInputStream = null;
       private Upload upload = null;
       private String fileName = null, mimeType = null;
       private Grid<FileListProperties> fileListGrid = null;

       public final static WebCommunityView newInstance(WebContentScreen screen) {
          vw.initBody();
          return vw;
       }

       protected void initBody() {

          VerticalLayout verticalLayout = new VerticalLayout();

          fileListGrid = new Grid<FileListProperties>();
          fileListGrid.addColumn(FileListProperties::getCreatedDate).setCaption("Date");
          fileListGrid.addColumn(FileListProperties::getFileName).setCaption("File Name");
          fileListGrid.addColumn(FileListProperties::getUserName).setCaption("User Name");
          fileListGrid.addComponentColumn(this::buildDownloadButton).setCaption("Download");

          fileListGrid.setItems(loadGridWithFileInfo());

          upload = new Upload("", this);
          upload.setImmediateMode(false);
          upload.addFailedListener((Upload.FailedListener) this);
          upload.addSucceededListener((Upload.SucceededListener) this);
          upload.addStartedListener((Upload.StartedListener) this);
          upload.addFinishedListener((Upload.FinishedListener) this);

          Label fileUploadLabel = new Label("Label"));

          verticalLayout.addComponent(currentListLabel);
          verticalLayout.addComponent(fileListGrid);
          verticalLayout.addComponent(fileUploadLabel);
          verticalLayout.addComponent(upload);
          mainbody.addComponent(verticalLayout);
       }

       @Override
       public void uploadSucceeded(SucceededEvent event) {

             try {
                //Model Layer
                fileUploadOperation.upload(pipedInputStream);
                fileUploadOperation.commit();

             } catch (Exception e) {
                e.printStackTrace();
             }

       }

       @Override
       public void uploadFailed(FailedEvent event) {
          if (event.getFilename() == null) {
             Notification.show("Upload failed", Notification.Type.HUMANIZED_MESSAGE);
          }

             try {
                            //Model Layer
                fileUploadOperation.abort();
             } catch (Exception e) {
                e.printStackTrace();
             }
       }


       public OutputStream receiveUpload(String filename, String mimeType) {
          this.fileName = filename;
          this.mimeType = mimeType;
          try {

             pipedOutputStream = new PipedOutputStream();

             new Thread() {
                public void run() {
                   try {
                      System.out.println("pipedInputStream Thread started");
                      pipedInputStream = new PipedInputStream(pipedOutputStream);

                   } catch (Exception e) {
                      e.printStackTrace();
                   }
                };
             }.start();

             if (filename == null || filename.trim().length() == 0) {
                screen.displayMessage("Please select a file to upload !", WebContentScreen.MESSAGE_TYPE_WARNING);
                upload.interruptUpload();
             } else {
                Properties properties = new Properties();
                properties.setProperty("NAME", fileName);
                properties.setProperty("MIME_TYPE", mimeType);
                //Model Layer
                fileUploadOperation.initialize(properties);

             }
          } catch (Exception e) {
             e.printStackTrace();
          }
          System.out.println("pipedOutputStream:"+pipedOutputStream);
          return pipedOutputStream;
       }

       private List<FileListProperties> loadGridWithFileInfo() {
          List<FileListProperties> list = null;
          DateFormat dateFormat = new SimpleDateFormat("dd-MMM-yyyy");

          try {
             list = new ArrayList<FileListProperties>(1);
             Collection<FileInfo> fileInfoList = fileCommandQuery.lstFilesForDownload();
             for (Iterator iterator = fileInfoList.iterator(); iterator.hasNext();) {

                FileInfo fileInfo = (FileInfo) iterator.next();
                Properties properties = fileInfo.getProperties();

                Collection<String> mandatoryParameters = fileInfo.getMandatoryProperties();

                FileListProperties fileListProperties = new FileListProperties();

                for (Iterator iterator2 = mandatoryParameters.iterator(); iterator2.hasNext();) {
                   String key = (String) iterator2.next();
                   String value = properties.getProperty(key);
                   if (key != null && key.equalsIgnoreCase("NAME")) {
                      fileListProperties.setFileName(value);
                   } else if (key != null && key.equalsIgnoreCase("USER_NAME")) {
                      fileListProperties.setUserName(value);
                   } else if (key != null && key.equalsIgnoreCase("CREATED_DATE")) {
                      Calendar calendar = Calendar.getInstance();
                      calendar.setTimeInMillis(1550566760000L);
                      fileListProperties.setCreatedDate(dateFormat.format(calendar.getTime()));
                   }
                }
                if (fileListProperties != null) {
                   list.add(fileListProperties);
                }
             }

          } catch (Exception e) {
             e.printStackTrace();
          } finally {
             dateFormat = null;
          }
          return list;
       }

       private Button buildDownloadButton(FileListProperties fileListProperties) {
          Button button = new Button("...");
          button.addClickListener(e -> downloadFile(fileListProperties));
          return button;
       }

       private void downloadFile(FileListProperties fileListProperties) {

       }
    }

公共类WebCommunityView实现Receiver、FailedListener、SucceedListener、StartedListener、FinishedListener{
私有PipedOutputStream PipedOutputStream=null；
私有PipedInputStream PipedInputStream=null；
私有上传=空；
私有字符串fileName=null，mimeType=null；
私有网格fileListGrid=null；
公共最终静态WebCommunityView新实例（WebContent屏幕）{
vw.initBody（）；
返回大众；
}
受保护的void initBody（）{
VerticalLayout VerticalLayout=新的VerticalLayout（）；
fileListGrid=新网格（）；
fileListGrid.addColumn（FileListProperties:：getCreatedDate）.setCaption（“日期”）；
fileListGrid.addColumn（FileListProperties:：getFileName）.setCaption（“文件名”）；
fileListGrid.addColumn（FileListProperties:：getUserName）.setCaption（“用户名”）；
fileListGrid.addComponentColumn（this:：buildDownloadButton）.setCaption（“下载”）；
setItems（loadGridWithFileInfo（））；
上传=新上传（“，此）；
upload.setImmediateMode（false）；
upload.addFailedListener（（upload.FailedListener）this）；
upload.addSucceededListener（（upload.SucceededListener）this）；
upload.addStartedListener（（upload.StartedListener）this）；
upload.addFinishedListener（（upload.FinishedListener）this）；
标签文件上传标签=新标签（“标签”）；
verticalLayout.addComponent（currentListLabel）；
addComponent（fileListGrid）；
addComponent（fileUploadLabel）；
verticalLayout.addComponent（上传）；
mainbody.addComponent（垂直布局）；
}
@凌驾
公共无效上载成功（SucceedeEvent事件）{
试一试{
//模型层
上传（pipedInputStream）；
fileUploadOperation.commit（）；
}捕获（例外e）{
e、 printStackTrace（）；
}
}
@凌驾
公共无效上载失败（FailedEvent事件）{
if（event.getFilename（）==null）{
Notification.show（“上传失败”，Notification.Type.HUMANIZED_消息）；
}
试一试{
//模型层
fileUploadOperation.abort（）；
}捕获（例外e）{
e、 printStackTrace（）；
}
}
public OutputStream receiveUpload（字符串文件名、字符串mimeType）{
this.fileName=文件名；
this.mimeType=mimeType；
试一试{
pipedOutputStream=新的pipedOutputStream（）；
新线程（）{
公开募捐{
试一试{
System.out.println（“pipedInputStream线程已启动”）；
pipedInputStream=新的pipedInputStream（PipedOutStream）；
}捕获（例外e）{
e、 printStackTrace（）；
}
};
}.start（）；
如果（filename==null | | filename.trim（）.length（）==0）{
screen.displayMessage（“请选择要上载的文件！”，WebContentScreen.MESSAGE\u TYPE\u警告）；
upload.interruptUpload（）；
}否则{
属性=新属性（）；
setProperty（“名称”，文件名）；
setProperty（“MIME_类型”，mimeType）；
//模型层
fileUploadOperation.initialize（属性）；
}
}捕获（例外e）{
e、 printStackTrace（）；
}
System.out.println（“pipedOutputStream:+pipedOutputStream”）；
返回管道输出流；
}
私有列表loadGridWithFileInfo（）{
List=null；
DateFormat DateFormat=新的SimpleDateFormat（“dd MMM yyyy”）；
试一试{
列表=新阵列列表（1）；
集合fileInfoList=fileCommandQuery.lstFilesForDownload（）；
for（Iterator Iterator=fileInfoList.Iterator（）；Iterator.hasNext（）；）{
FileInfo FileInfo=（FileInfo）迭代器.next（）；
Properties=fileInfo.getProperties（）；
Collection mandatoryParameters=fileInfo.getMandatoryProperties（）；
FileListProperties FileListProperties=新的FileListProperties（）；
for（迭代器迭代器2=mandatoryParameters.Iterator（）；迭代器2.hasNext（）；）{
字符串键=（字符串）迭代器2.next（）；
字符串值=properties.getProperty（键）；
if（key！=null&&key.equalsIgnoreCase（“NAME”））{
fileListProperties.setFileName（值）；
}else if（key！=null&&key.equalsIgnoreCase（“用户名”））{
fileListProperties.setUserName（值）；
}else if（key！=null&&key.equalsIgnoreCase（“创建日期”））{
C