I am trying to execute a function from a class in a jar file dynamically. I have the location of the jar file, the name of the class and the function in it as strings.
I looked at these questions, but none of the answers worked for me:
How should I load Jars dynamically at runtime?
ClassNotFoundException while trying to load class from external JAR at runtime
How to load a jar file at runtime
Load jar dynamically at runtime?
Here is what I've got so far: In the main program:
public class Main { public static void main(String[] args) { File file = new File("E:\\DeSKtop\\hw.jar"); String lcStr = "Main1"; URL jarfile; try { jarfile = new URL("jar", "","file:" + file.getAbsolutePath()+"!/"); URLClassLoader cl = URLClassLoader.newInstance(new URL[] {jarfile }); Class loadedClass = cl.loadClass(lcStr); Method method = loadedClass.getDeclaredMethod("returnHW"); Object instance = loadedClass.newInstance(); Object result = method.invoke(instance); //System.out.println(method.invoke()); } catch (MalformedURLException e) { // TODO Auto-generated catch block e.printStackTrace(); } //System.out.println(loadLibrary(myJar)); catch (ClassNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (NoSuchMethodException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (SecurityException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (InstantiationException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IllegalAccessException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IllegalArgumentException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (InvocationTargetException e) { // TODO Auto-generated catch block e.printStackTrace(); } } In the jar file I'm trying to load:
public class Main1 { public static void main(String[] args) { } public static String returnHW() { System.out.println("HlloWOrld");; return "Hello Wrld!"; } } When I try to run the main program I get this:
java.lang.ClassNotFoundException: Main1 at java.net.URLClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at java.net.FactoryURLClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at Main.main(Main.java:22) Can you tell me what I'm doing wrong? Thank you in advance.
