Vaadin upload with PipedInputStream & PipedOutputStream example - vaadin

Question

I just started learning Vaadin 8 and my first example is Upload button. I was stuck with an issue where I could not solve the problem for many hours and hours.
Here it is,
I am returning PipedOutputStream in the receiveUpload method,
Here is the code for receiveUpload method,
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;
}
In the uploadSucceeded method, I need to take the pipedinputstream and send it another method to load the stream into the database
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();
}
}
When I was running the application, it hangs out for a long time and I could not figure out where it is. Later I could notice that both piped input and piped output streams should be created in separate threads or at least one of them in a separate thread but don't know how to handle it.
Any help
I am pasting the complete class for more information,
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) {
}
}

Answer 1

The problem in your example is that you need to do the actual file handling in a separate thread. The Viritin add-on contains a component called UploadFileHandler that simplifies this kind of usage a lot. It will provide you InputStream to consume. The integration test for the component contains this kind of usage example.
Also, my recent blog entry about the subject might help.