intellij-sdk-code-samples/topics/basics/architectural_overview/psi_elements.md

PSI Elements

Introduction to PSI elements.

A PSI (Program Structure Interface) file represents a hierarchy of PSI elements (so-called PSI trees). A single PSI file (itself being a PSI element) may expose several PSI trees in specific programming languages (see ). A PSI element, in its turn, can have child PSI elements.

PSI elements and operations at the level of individual PSI elements are used to explore the source code's internal structure as it is interpreted by the IntelliJ Platform. For example, you can use PSI elements to perform code analysis, such as code inspections or intention actions.

The PsiElement class is the common base class for PSI elements.

PSI classes for specific languages usually start with a language prefix, for example, JsonArray.

The Java PSI API, developed many years ago when there was no plan to support other languages, uses the Psi prefix, for example, PsiIdentifier or PsiElementFactory. Don't confuse Java with the core PSI API.

To use Java PSI API, add a dependency on the Java plugin.

How do I get a PSI element?

Context	API
Action	AnActionEvent.getData(CommonDataKeys.PSI_ELEMENT) Note: If an editor is currently open and the element under caret is a reference, this will return the result of resolving the reference.
PSI File	PsiFile.findElementAt(offset) - This returns a leaf element at the specified offset, normally a lexer token. Use PsiTreeUtil.getParentOfType() to find the element of the exact type. PsiRecursiveElementWalkingVisitor
Reference	PsiReference.resolve()

What can I do with PSI elements?

See and .