I have solved this problem for a single class loader. I needed reflection to write code to inspect JUnit tests and report on ignored tests.
/**
* Attempts to list all the classes in the specified package as determined
* by the context class loader
*
* @param pckgname
* the package name to search
* @return a list of classes that exist within that package
* @throws ClassNotFoundException
* if something went wrong
*/
private static List<Class> getClassesForPackage(String pckgname) throws ClassNotFoundException {
// This will hold a list of directories matching the pckgname. There may be more than one if a package is split over multiple jars/paths
ArrayList<File> directories = new ArrayList<File>();
try {
ClassLoader cld = Thread.currentThread().getContextClassLoader();
if (cld == null) {
throw new ClassNotFoundException("Can't get class loader.");
}
String path = pckgname.replace('.', '/');
// Ask for all resources for the path
Enumeration<URL> resources = cld.getResources(path);
while (resources.hasMoreElements()) {
directories.add(new File(URLDecoder.decode(resources.nextElement().getPath(), "UTF-8")));
}
} catch (NullPointerException x) {
throw new ClassNotFoundException(pckgname + " does not appear to be a valid package (Null pointer exception)");
} catch (UnsupportedEncodingException encex) {
throw new ClassNotFoundException(pckgname + " does not appear to be a valid package (Unsupported encoding)");
} catch (IOException ioex) {
throw new ClassNotFoundException("IOException was thrown when trying to get all resources for " + pckgname);
}
ArrayList<Class> classes = new ArrayList<Class>();
// For every directory identified capture all the .class files
for (File directory : directories) {
if (directory.exists()) {
// Get the list of the files contained in the package
String[] files = directory.list();
for (String file : files) {
// we are only interested in .class files
if (file.endsWith(".class")) {
// removes the .class extension
try
{
classes.add(Class.forName(pckgname + '.' + file.substring(0, file.length() - 6)));
}
catch (NoClassDefFoundError e)
{
// do nothing. this class hasn't been found by the loader, and we don't care.
}
}
}
} else {
throw new ClassNotFoundException(pckgname + " (" + directory.getPath() + ") does not appear to be a valid package");
}
}
return classes;
}
I based my solution on the code in this thread:
