XPath

The :tools:xpath module exposes the JavaParser AST as an XML document and queries it with XPath 1.0. This is the power tool for ad-hoc structural queries — “every method with a requires clause”, “all this accesses inside loops” — expressed as standard XPath instead of visitor code.

The mapping

JavaParser nodes become elements; the document root is a project element wrapping one or more compilation units:

project
└── compilationUnit [@package=..., @name=...]
    └── classOrInterfaceDeclaration [@name="Account"]
        └── methodDeclaration [@name="withdraw", @signature=..., ...]
            ├── parameter [@name="amount", @type="int"]
            ├── blockStmt ...
            └── jmlContract ...

• JPDocument implements the W3C Document interface (read-only; creation operations throw DOMException.NOT_SUPPORTED_ERR).
• JPRootElement is the project root built from a list of CompilationUnits.
• JPElement wraps any single AST node; node properties (name, modifiers, type, begin/end line, …) are available as attributes, and pseudo attributes (via PseudoAttributeProvider) expose computed values such as @name, @signature or @beginLine.

Usage

object XPathFacade {
    // serialize a compilation unit as indented XML
    @Throws(TransformerException::class)
    fun printXml(n: CompilationUnit): String

    // evaluate an XPath expression and print every matching AST node
    @Throws(XPathExpressionException::class)
    fun query(n: CompilationUnit, query: String?)
}

Because the document is backed by the live AST nodes, the result set of a query contains the actual JavaParser nodes — (res.item(i) as JPElement).astNode gives you the Node to keep working with:

XPathFacade.query(cu, "//methodDeclaration[@name='withdraw']")

Typical queries (standard XPath 1.0):

//methodDeclaration[contains(@modifiers, 'static')]   static methods
//jmlContract                                         all contracts
//classOrInterfaceDeclaration[@name='Account']//fieldDeclaration

CLI

jmltk xpath "//methodDeclaration[@name='foo']" File.java

The xpath subcommand is registered in the CLI (help: “Evaluate XPath queries on a set of Java/JML files”) but its run() is not yet implemented — use XPathFacade.query programmatically in the meantime.