# File View Providers Handling multiple languages PSI trees in a single file. A file view provider ([`FileViewProvider`](%gh-ic%/platform/core-api/src/com/intellij/psi/FileViewProvider.java)) manages access to multiple PSI trees within a single file. For example, a JSPX page has a separate PSI tree for the Java code in it (`PsiJavaFile`), a separate tree for the XML code (`XmlFile`), and a separate tree for JSP as a whole ([`JspFile`](%gh-ic%/java/jsp-openapi/src/com/intellij/psi/jsp/JspFile.java)). Each of the PSI trees covers the entire contents of the file and contains special "outer language elements" in the places where contents in a different language can be found. A `FileViewProvider` instance corresponds to a single `VirtualFile`, a single `Document`, and can retrieve multiple `PsiFile` instances. ## How do I get a `FileViewProvider`? | Context | API | |---------------------------------|------------------------------------------------------------------------------------------------------------------------| | [PSI File](psi_files.md) | [`PsiFile.getViewProvider()`](%gh-ic%/platform/core-api/src/com/intellij/psi/PsiFile.java) | | [Virtual File](virtual_file.md) | [`PsiManager.getInstance(project).findViewProvider()`](%gh-ic%/platform/core-api/src/com/intellij/psi/PsiManager.java) | ## What can I do with a `FileViewProvider`? * To get the set of all languages for which PSI trees exist in a file: `fileViewProvider.getLanguages()` * To get the PSI tree for a particular language: `fileViewProvider.getPsi(language)`. For example, to get the PSI tree for XML, use `fileViewProvider.getPsi(XMLLanguage.INSTANCE)`. * To find an element of a particular language at the specified offset in the file: `fileViewProvider.findElementAt(offset, language)` ## How do I extend the `FileViewProvider`? To create a file type that has multiple interspersing trees for different languages, a plugin must contain an extension to the . Implement [`FileViewProviderFactory`](%gh-ic%/platform/core-api/src/com/intellij/psi/FileViewProviderFactory.java) and return your `FileViewProvider` implementation from `createFileViewProvider()` method. Register as follows in [plugin.xml](plugin_configuration_file.md): ```xml ``` Where `$FILE_TYPE$` refers to the type of the file being created (for example, "JSF").