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URLClassLoader: Modify Classpath At Runtime Java code example - Click here to copy ->>>

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The system classloader (ClassLoader.getSystemClassLoader()) is a subclass of URLClassLoader.

It can be casted into a URLClassLoader and used as one.


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

public class ClassPathHacker {

   private static final Class[] parameters = new Class[]{URL.class};

   public static void addFile(String s) throws IOException {
      File f = new File(s);
   }//end method

   public static void addFile(File f) throws IOException {
   }//end method

   public static void addURL(URL u) throws IOException {

      URLClassLoader sysloader = (URLClassLoader) ClassLoader.getSystemClassLoader();
      Class sysclass = URLClassLoader.class;

      try {
         Method method = sysclass.getDeclaredMethod("addURL", parameters);
         method.invoke(sysloader, new Object[]{u});
      } catch (Throwable t) {
         throw new IOException("Error, could not add URL to system classloader");
      }//end try catch

   }//end method

}//end class



The list of classes which were used on this page you can find below. The links to Java API contain official SUN documentation about all used classes.










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