Loading jars from Lib folder for standalone Jar execution

Loading Jars While Booting of application from separate external folder 

I have faced an issue with dynamic jars loading to start the service without giving any classpath in MANIFEST file inside jar file.

I have spent lot much time on this to get on to the solution, but no luck. I found some info on stackoverflow pertaining to this. I wanna share that with you today with slight modifications make use as simple jar file.

Here is the simple class I wrote and also created a simple jar file for direct usage.

Here is the Reference for source code url.

link to source code

You can also download direct jar file from above URL under "dist"  directory.

Sample Class::

package com.rnd.java.bootup;

import java.io.File;
import java.lang.reflect.Method;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.List;

import org.apache.commons.io.FileUtils;

public class Bootup 
{
 public void run(String[] args) throws Exception 
 {
  
  List jars  =  (List) FileUtils.listFiles(new File(args[1]), null, true);
  URL urls[] =  FileUtils.toURLs(jars.toArray(new File[jars.size()]));
  
  for (int i = 0; i < urls.length; i++) 
  {
   loadMe(urls[i]);
   System.out.println(urls[i]);
  }
  
  Object[] arguments = new Object[]{args};
  Class classToLoad = Class.forName(args[0]);
  Method method = classToLoad.getMethod("main",String[].class);
  Object result = method.invoke (null,arguments);
  System.out.println(result);
 }
 
 
 private void loadMe(URL url) {
  try {
      
      URLClassLoader classLoader = (URLClassLoader)ClassLoader.getSystemClassLoader();
      Method method = URLClassLoader.class.getDeclaredMethod("addURL", URL.class);
      method.setAccessible(true);
      method.invoke(classLoader, url);
  } catch (Exception ex) {
      ex.printStackTrace();
  }

 }
 
 
 /**
  * How to use ?
  * java -jar bootup.jar com.company.application.mainclass lib main 
  * 
  * 
  * @param args
  */
 public static void main(String[] args) 
 {
  if(args.length==0)
  {
   StringBuilder help = new StringBuilder();
   help.append("Usage !!! \n java -jar bootup.jar fullyQualifiedClassName libFolderName method2Call ");
   System.out.println(help.toString());
   throw new IllegalArgumentException("Wrong number of arguments!!!!");
  }else if(args.length==1)
  {
   args = new String[]{args[0],"lib","main"};
  }else if(args.length==2)
  {
   args = new String[]{args[0],args[1],"main"};
  }
  try{
   new Bootup().run(args);
  
  }catch(Exception e)
  {
   e.printStackTrace();
  }
 }

}