Don't know package of class in a jar using URLClassLoader

Question

Hello,
i want to load a class out of a jar file but the only thing i know is the classname its the same as the jarname. the problem now is i packed the plugin as nice with packages and my Loader won't find the class without package, what can i do to know the package?
i don't have any main method because it's a plugin loading. i know der should be a possibility to loop through all classes?! or even to find a class implementing an interface (but that was something with ServiceLoader)...how can i do it?
for(int i = 0; files != null && i < files.length; i++) {
     MyClassLoader pluginLoader = null;
     try {
          pluginLoader = new MyClassLoader(MyConstants.MODULES_PATH+files);
     } catch(MalformedURLException e) {
          System.out.println("Exception: " + e.getMessage());
     // cut off extension for className
     int dot = files[i].lastIndexOf(MyConstants.MODULE_EXTENSION);
     String className = files[i].substring(0, dot);
     MyPluginInterface plugin = null;
     try {
          plugin = (MyPluginInterface)pluginLoader.findClass(className).newInstance();
     } catch(Exception e) {
          System.out.println("Exception: " + e.getMessage());
this works (for one of the jars with this package then):plugin = (MyPluginInterface)pluginLoader.findClass("my.package.in.jar."+className).newInstance();
public class MyClassLoader extends URLClassLoader {
     public MyClassLoader (String filenName) throws MalformedURLException {
          super(new URL[]{new File(filenName).toURI().toURL()}, MyClassLoader.class.getClassLoader());
     public Class<?> findClass(String name) throws ClassNotFoundException {
          return super.findClass(name);
thx for you help!                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       

Answer 1

YES! just a bit of work and it's running nice :-)
if(!(Constants.MODULES_PATH.endsWith("/"))) Constants.MODULES_PATH = Constants.MODULES_PATH + "/";
File path = new File(Constants.MODULES_PATH);
if(path.exists() && path.isDirectory()) {
     // find all .jar files
     String[] files = path.list(new FilenameFilter() {
          public boolean accept(File d, String name) { return name.endsWith(Constants.MODULE_EXTENSION); }
     for(int i = 0; files != null && i < files.length; i++) {
          // create class loader for jar
          MySystemClassLoader classLoader = null;
          try {
               classLoader = new MySystemClassLoader(Constants.MODULES_PATH+files);
          } catch(MalformedURLException e) {
               System.out.println("Exception: " + e.getMessage());
          // load service(s)/module(s) (can be more than one in a jar!)
          ServiceLoader<ModuleInterface> moduleLoader = ServiceLoader.load(ModuleInterface.class, classLoader);
          for(ModuleInterface module : moduleLoader) {
               System.out.println("load module: "+module.getClass().getName()+"!");
}and this as class loader (given to the service loader)public class MySystemClassLoader extends URLClassLoader {
     public MySystemClassLoader(String filenName) throws MalformedURLException {
          super(new URL[]{new File(filenName).toURI().toURL()}, MySystemClassLoader.class.getClassLoader());
     public Class<?> findClass(String name) throws ClassNotFoundException {
          return super.findClass(name);
in the jar-file (module/service) you need a file named as the interface (path.to.package.ModuleInterface) inside of a folder "META-INF/services/" and contains just as a string (path.to.package.ModuleImplementation) the name of the implementaion class (in the jar-file)
Edited by: mrp_cologne on Jul 21, 2008 3:55 AM