Find out which classes of a given API are used

Question

In a Java Project of mine, I would like to find out programmatically which classes from a given API are used. Is there a good way to do that? Through source code parsing or bytecode parsing maybe? Because Reflection won't be of any use, I'm afraid.

To make things simpler: there are no wildcard imports (import com.mycompany.api.*;) anywhere in my project, no fully qualified field or variable definitions (private com.mycompany.api.MyThingy thingy;) nor any Class.forName(...) constructs. Given these limitations, it boils down to parsing import statements, I guess. Is there a preferred approach to do this?

Answer 1

Something like this perhaps:

import java.io.*;
import java.util.Scanner;
import java.util.regex.Pattern;

public class FileTraverser {

    public static void main(String[] args) {
        visitAllDirsAndFiles(new File("source_directory"));
    }

    public static void visitAllDirsAndFiles(File root) {
        if (root.isDirectory())
            for (String child : root.list())
                visitAllDirsAndFiles(new File(root, child));
        process(root);
    }

    private static void process(File f) {

        Pattern p = Pattern.compile("(?=\\p{javaWhitespace}*)import (.*);");
        if (f.isFile() && f.getName().endsWith(".java")) {
            try {
                Scanner s = new Scanner(f);
                String cls = "";
                while (null != (cls = s.findWithinHorizon(p, 0)))
                    System.out.println(cls);
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            }
        }
    }
}

You may want to take comments into account, but it shouldn't be too hard. You could also make sure you only look for imports before the class declaration.

Answer 2

I use DependencyFinder exactly for that purpose. It can analyse bytecode and extract all dependencies, then dump a report in txt or xml format (see the DependencyExtractor tool). You should be able to programatically analyse the report from your application's code.

I have integrated this in my build process in order to check that certain APIs are NOT used by an application.

Answer 3

I think the following might help you out:

1. Class Dependency Analyzer
2. Dependency Finder

Answer 4

1. Compiler Tree API
2. byte code analysis - the fully qualified names should be in the constant pool

Answer 5

You may want to use STAN for that.

The "Couplings View" visualizes the dependencies to your API in a nice graph.

Answer 6

If you use Eclipse. Try using the profiling tools. It doesn't only tells which classes are being used, but tells much more about it. The results will be something like:

There is a very good quickstart at:

http://www.eclipse.org/tptp/home/documents/tutorials/profilingtool/profilingexample_32.html