IntelliJ Platform SDK DevGuide

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Virtual Files

A virtual file VirtualFile is the IntelliJ Platform’s representation of a file in a file system (VFS). Most commonly, a virtual file is a file in your local file system. However, the IntelliJ Platform supports multiple pluggable file system implementations, so virtual files can also represent classes in a JAR file, old revisions of files loaded from a version control repository, and so on.

The VFS level deals only with binary content. You can get or set the contents of a VirtualFile as a stream of bytes, but concepts like encodings and line separators are handled on higher system levels.

How do I get a virtual file?

  • From an action: e.getData(PlatformDataKeys.VIRTUAL_FILE). If you are interested in multiple selection, you can also use e.getData(PlatformDataKeys.VIRTUAL_FILE_ARRAY).
  • From a path in the local file system: LocalFileSystem.getInstance().findFileByIoFile()
  • From a PSI file: psiFile.getVirtualFile() (may return null if the PSI file exists only in memory)
  • From a document: FileDocumentManager.getInstance().getFile()

What can I do with it?

Typical file operations are available, such as traverse the file system, get file contents, rename, move, or delete. Recursive iteration should be performed using VfsUtilCore.iterateChildrenRecursively to prevent endless loops caused by recursive symlinks.

Where does it come from?

The VFS is built incrementally, by scanning the file system up and down starting from the project root. New files appearing in the file system are detected by VFS refreshes. A refresh operation can be initiated programmatically using (VirtualFileManager.getInstance().refresh() or VirtualFile.refresh()). VFS refreshes are also triggered whenever file system watchers receive file system change notifications (available on the Windows and Mac operating systems).

As a plugin developer, you may want to invoke a VFS refresh if you need to access a file that has just been created by an external tool through the IntelliJ Platform APIs.

How long does a virtual file persist?

A particular file on disk is represented by equal VirtualFile instances for the entire lifetime of the IDEA process. There may be several instances corresponding to the same file, and they can be garbage-collected. The file is a UserDataHolder, and the user data is shared between those equal instances. If a file is deleted, its corresponding VirtualFile instance becomes invalid (the isValid() method returns false and operations cause exceptions).

How do I create a virtual file?

Usually you don’t. As a rule, files are created either through the PSI API or through the regular API.

If you do need to create a file through VFS, you can use the VirtualFile.createChildData() method to create a VirtualFile instance and the VirtualFile.setBinaryContent() method to write some data to the file.

How do I get notified when VFS changes?

Implement the BulkFileListener interface and subscribe to the message bus topic VirtualFileManager.VFS_CHANGES. For example:

project.getMessageBus().connect().subscribe(VirtualFileManager.VFS_CHANGES, new BulkFileListener() { @Override public void after(@NotNull List<? extends VFileEvent> events) { // handle the events } });

See Message Infrastructure and Plugin Listeners for more details.

For a non-blocking alternative, starting with version 2019.2 of the platform, see AsyncFileListener

Plugins targeting versions 2017.2 or older of the platform can use the now deprecated VirtualFileManager.addVirtualFileListener() method which allows you to receive notifications about all changes in the VFS.

Are there any utilities for analyzing and manipulating virtual files?

VfsUtil and VfsUtilCore provide utility methods for analyzing files in the Virtual File System.

You can use ProjectLocator to find the projects that contain a given virtual file.

How do I extend VFS?

To provide an alternative file system implementation (for example, an FTP file system), implement the VirtualFileSystem class (most likely you’ll also need to implement VirtualFile), and register your implementation as an application component.

To hook into operations performed in the local file system (for example, if you are developing a version control system integration that needs custom rename/move handling), implement the LocalFileOperationsHandler interface and register it through theLocalFileSystem.registerAuxiliaryFileOperationsHandler method.

What are the rules for working with VFS?

See IntelliJ Platform Virtual File System for a detailed description of the VFS architecture and usage guidelines.

Last modified: 19 February 2020