Documents

A document is an editable sequence of Unicode characters, which typically corresponds to the text contents of a virtual file. Line breaks in a document are always normalized to \n. The IntelliJ Platform handles encoding and line break conversions when loading and saving documents transparently.

How do I get a document?

• From an action: e.getData(PlatformDataKeys.EDITOR).getDocument()
• From a virtual file: FileDocumentManager.getDocument(). This call forces the document content to be loaded from disk if it wasn’t loaded previously; if you’re only interested in open documents or documents which may have been modified, use FileDocumentManager.getCachedDocument() instead.
• From a PSI file: PsiDocumentManager.getInstance().getDocument() or PsiDocumentManager.getInstance().getCachedDocument()

What can I do with a Document?

You may perform any operations that access or modify the file contents on “plain text” level (as a sequence of characters, not as a tree of Java elements).

Where does a Document come from?

Document instances are created when some operation needs to access the text contents of a file (in particular, this is needed to build the PSI for a file). Also, document instances not linked to any virtual files can be created temporarily, for example, to represent the contents of a text editor field in a dialog.

How long does a Document persist?

Document instances are weakly referenced from VirtualFile instances. Thus, an unmodified Document instance can be garbage-collected if it isn’t referenced by anyone, and a new instance will be created if the document contents is accessed again later. Storing Document references in long-term data structures of your plugin will cause memory leaks.

How do I create a Document?

If you need to create a new file on disk, you don’t create a Document: you create a PSI file and then get its Document. If you need to create a Document instance which isn’t bound to anything, you can use EditorFactory.createDocument.

How do I get notified when Documents change?

• Document.addDocumentListener allows you to receive notifications about changes in a particular Document instance.
• EditorFactory.getEventMulticaster().addDocumentListener allows you to receive notifications about changes in all open documents.
• Subscribe to AppTopics#FILE_DOCUMENT_SYNC on any level bus to receive notifications when any Document is saved or reloaded from disk.

What are the rules of working with Documents?

The general read/write action rules are in effect. In addition to that, any operations which modify the contents of the document must be wrapped in a command (CommandProcessor.getInstance().executeCommand()). executeCommand() calls can be nested, and the outermost executeCommand call is added to the undo stack. If multiple documents are modified within a command, undoing this command will by default show a confirmation dialog to the user.

If the file corresponding to a Document is read-only (for example, not checked out from the version control system), document modifications will fail. Thus, before modifying the Document, it is necessary to call ReadonlyStatusHandler.getInstance(project).ensureFilesWritable() to check out the file if necessary.

All text strings passed to Document modification methods (setText, insertString, replaceString) must use only \n as line separators.

Are there any utilities available for working with Documents?

DocumentUtil contains utility methods for Document processing. This allows you to get information like the text offsets of particular lines. This is particularly useful when you need text location/offset information about a given PsiElement.