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Please be aware that there is newer version of documentation available for Webswing. Documentation 24.1


File system

Swing applications running inside Webswing are ultimately using the file system of the server where Webswing is running. This causes problems to applications that consume or generate files and interact with file system.

Webswing solves this problem by providing an automatic JFileChooser integration dialog, which offers users ability to interact with server's file system by uploading, downloading and deleting files from the browser.

file dialog


It is possible to disable upload, download or delete files in the application configuration.

Isolated file system

If the users are not supposed to have access to the full servers file system, Webswing offers the option to limit the access to isolated folder that they are allowed to interact with. This isolatedFs setting can be set in application configuration. If it is enabled, the user will only see folder "upload" in homeDir folder.

isolated File System


Webswing implements seamless printing support, which works out of the box without any change needed in your application. Webswing generates a PDF file from the printed document and opens it in a new browser tab using PDF.js viewer.

Printing integration handles printing using:

  • Toolkit.getDefaultToolkit().getPrintJob() method
  • PrinterJob.getPrinterJob()
  • multi paged documents
  • landscape and portrait orientation

Printing is demonstrated in Webswing Demo application with sample source code included.

isolated File System

Custom print service

Since Webswing 22.2 the print service is customizable. Please follow these steps:

  1. Implement a print service class that implements "org.webswing.ext.services.PdfService" interface included in webswing-app-toolkit project.
  2. Put JAR with the class in /extensions folder in webswing installation folder.
  3. Run application with system property -Dorg.webswing.ext.services.PdfService=com.company.CustomPdfService


Webswing has a built-in clipboard integration. Due to various browser security limitations some clipboard operations are limited at the moment.


When the user triggers copy operation from the Swing application by pressing CTRL+C or in menu option, Webswing analyzes the data written to clipboard and notifies the client what type of data is available in clipboard by small dialog.

Webswing recognizes 5 basic types.

  1. Plain text
  2. HTML

html copy dialog

  1. Image

image copy dialog

  1. Files

file copy dialog

  1. Other (i.e. application specific types)

This dialog informs the user that data is available in the Swing clipboard. To copy the Plain text or HTML type to local clipboard, user can press CTRL+C again while the dialog is visible. For copying the image, the user has to use the browser default behavior to copy the image to the local clipboard.

Since version 22.2 Webswing uses browser's Clipboard API to automatically send data from Webswing to local clipboard. If user's browser supports Clipboard API the copied data will be automatically sent to local clipboard without showing the copy dialog and pressing CTRL+C again. In case user's browser does not support Clipboard API, the copy dialog shows as a fallback. Note that Clipboard API is supported only in secure contexts, i.e. only with HTTPS.

If the Swing clipboard contains files and allowDownload option is enabled, the user will be presented with a list of links allowing him to download those files from the Swing application.

Note: isolatedFs option does not apply here. Access is not limited to files in the isolated folder.


Paste operation can be triggered by CTRL+V keyboard shortcut. But here it gets a little tricky, because we have our Swing clipboard data sitting on the server and we have a local browser clipboard data. So we need to decide which one to use for the paste operation.

The solution is simple. If the clipboard dialog is open, we use the Swing clipboard, because we know the user has just copied some data there. If the clipboard is not visible, we try to get the data from the local browser clipboard.

minimized copy dialog

Note: if paste operation is triggered from context menu, it will always use the Swing clipboard data.

Pasting from Swing clipboard All types are accessible to application if pasting from Swing clipboard.

Pasting from local browser clipboard See the following matrix for supported types based on browser.

Browser Supported content types
Chrome Plain text, HTML, Images
Firefox Plain text, HTML
IE Plain text, HTML

Automatic clipboard synchronization

You can force to synchronize the local browser clipboard before pasting to Webswing using a startup option. With this option turned on, Webswing will always use the contents of local browser clipboard (if available).

var webswingInstance0 = {
    options: {
        syncClipboard: true,

To enable the customization first follow the steps from Webswing Branding to get a custom index.html.


The AWT framework Desktop class is the default interface for triggering OS specific operations like edit file or open link. Webswing implements this interface and interprets these commands in a web browser-friendly way.

Method Webswing operation
browse Opens the specified link in new tab
edit Referenced file is downloaded
mail Opens a new email window in default mail client
open Referenced file is downloaded
print Referenced file is downloaded, PDF file is displayed in new tab with pdf.js

See File viewers for configuration of handling Desktop class methods.