Package com.vaadin.flow.server.streams

Class FileDownloadHandler

java.lang.Object
com.vaadin.flow.server.streams.TransferProgressAwareHandler<DownloadEvent,FileDownloadHandler>
com.vaadin.flow.server.streams.AbstractDownloadHandler<FileDownloadHandler>
com.vaadin.flow.server.streams.FileDownloadHandler
All Implemented Interfaces:
DownloadHandler, ElementRequestHandler, Serializable
public class FileDownloadHandler extends AbstractDownloadHandler<FileDownloadHandler>
Download handler for use with a given File that will be read and written as binary data to the response.

Byte range requests, which media players use to seek, are answered with the requested part of the file.

Since:
24.8
See Also:

  • Constructor Details

    • FileDownloadHandler

      public FileDownloadHandler(File file)
      Create a download handler for given file. Url postfix will be used as file.getName().

      The downloaded file name and download URL postfix will be set to file.getName(). If you want to use a different file name, use FileDownloadHandler(File, String) instead.

      Parameters:
      file - file to download

    • FileDownloadHandler

      public FileDownloadHandler(File file, String fileNameOverride)
      Create a download handler for given file.

      The downloaded file fileNameOverride and download URL postfix will be set to fileNameOverride.

      Parameters:
      file - file to download
      fileNameOverride - used as a downloaded file name (overrides file.getName()) and also as a download request URL postfix, e.g. /VAADIN/dynamic/resource/0/5298ee8b-9686-4a5a-ae1d-b38c62767d6a/my-file.txt

  • Method Details

    • handleDownloadRequest

      public void handleDownloadRequest(DownloadEvent downloadEvent) throws IOException
      Description copied from interface: DownloadHandler
      Method that is called when the client wants to download from the url stored for this specific handler registration.

      Once this method has been called, the download is no longer bound to the owner component's lifecycle and is not interrupted by detaching the owner or by closing the browser tab, see the class-level documentation.

      Parameters:
      downloadEvent - download event containing the necessary data for writing the response
      Throws:
      IOException - if an IO error occurred during download

    • isRangeRequestsEnabled

      public boolean isRangeRequestsEnabled()
      Returns whether this handler answers byte range requests, which media players use to seek and browsers use to resume a download. Safari does not play audio or video from a handler that does not answer them.

      A handler that does not answer them sends the whole content for every request. A handler that does may still send the whole content for a particular response, for example when the length of its content is not known. The default implementation returns false.

      In development mode, a built-in handler logs a warning the first time that a handler of its class serves the whole content for a byte range request, for example because ranges are not enabled or the length of the content is unknown.

      Range requests are always answered for a file.

      Returns:
      true if the handler is configured to answer byte range requests

    • getUrlPostfix

      public String getUrlPostfix()
      Description copied from interface: ElementRequestHandler
      Optional URL postfix allows appending an application-controlled string, e.g. the logical name of the target file, to the end of the otherwise random-looking download URL. If defined, requests that would otherwise be routable are still rejected if the postfix is missing or invalid. Postfix changes the last segment in the resource url.
      Returns:
      String optional URL postfix, or null for "".

    • getTransferContext

      protected TransferContext getTransferContext(DownloadEvent transferEvent)
      Description copied from class: TransferProgressAwareHandler
      This method is used to get the transfer context from the transfer events (e.g. DownloadEvent).
      Overrides:
      getTransferContext in class AbstractDownloadHandler<FileDownloadHandler>
      Parameters:
      transferEvent - the transfer event
      Returns:
      the transfer context