javac.exe AST programmatic access example

Question

Is it possible to access the Abstract Syntax Tree(AST) inside the javac.exe programmatically? Could you provide an example?

Answer 1

Compile and run this with -cp tools.jar (where you have to specify the location of your tools.jar, obviously).

import com.sun.source.util.Trees;
import javax.tools.JavaCompiler;
import javax.tools.StandardJavaFileManager;
import javax.tools.ToolProvider;

public class JCTreeTest {
    private static final JavaCompiler javac
            = ToolProvider.getSystemJavaCompiler();

    public static void main(String[] args) {
        final StandardJavaFileManager jfm
                = javac.getStandardFileManager(null, null, null);
        final JavaCompiler.CompilationTask task
                = javac.getTask(null, jfm, null, null, null,
                  jfm.getJavaFileObjects(args));
        final Trees trees = Trees.instance(task);
        // Do stuff with "trees"
    }
}

It compiles and runs for me, though I have not played with the trees stuff myself, so you'll have to read the javadoc yourself. :-) Good luck!