NoClassDefFoundError

Hello,

So, I've imported a java jar called Reflections. You can find it here: https://code.google.com/archive/p/reflections/

I've downloaded this to allow me to get all classes that extend a certain class. The problem is at runtime, I get an NCDFE error since the server cannot find this jar file.

I get the error at this line:

Code:

        Reflections reflections = new Reflections("testPackage.Dungeons.MobSpells");    

I've checked my build path, classpath, refreshed, and cleaned my project. My code also has no errors, and I've checked to make sure that the import path is correct. Is there any way I could solve this problem, or is there any other method to get all classes that extend another class?

Thanks,
WarlordWeaponry

 

@mine2012craft
What exactly are you trying to achieve? There is most likely a better way to do it that does not require reflection.

 

I'm trying to get all classes that extend an abstract class. I then get the abstract method from the class that I have chosen, and use it. I've downloaded the jar file above because it seemed like the simplest way to do so.

 

@mine2012craft

Here a method for list all the class of your jar. Just check if the super class is not null and if it's equal to what you want.

Code:

    
    public void getClasses() throws URISyntaxException
    {
        File file = new File(this.getClass().getProtectionDomain().getCodeSource().getLocation().toURI().getPath());
       
        try
        {
            @SuppressWarnings("resource")
            JarFile jar = new JarFile(file);
           
            for (Enumeration<JarEntry> entry = jar.entries(); entry.hasMoreElements();)
            {
                JarEntry e = entry.nextElement();
                String name = e.getName().replace("/", ".");
               
                if (name.endsWith(".class"))
                {
                    name = name.split(".class")[0];
                    Class<?> c = Class.forName(name);
                }
            }
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
    }

 

Thanks for the response, but the problem is that the method needs to be static. I'll be using this in other classes, and not this one only.

 

@mine2012craft And you don't know how to turn a method static ?

 

@Caderape2 I was tired last night when I imported that code, and didn't really try to make it static. I'll try again however.

@timtower Ok, sure I'll give it a shot

EDIT: Alright, I got it to work through getting an instance of the MobSpell class thru static methods. I'm getting the classes successfully too, but the problem is the abstract method is not working for each of the classes.

Here is the code I'm using. It's for debugging purposes by the way.

Code:

for (MobSpell msp : ms.getClasses()){
                    msp.cast();
                    System.out.println(msp.toString());
                }

 

bump

 

@mine2012craft Show the updated method also.
ms.getClasses()

 

Code:

    public  LinkedList<MobSpell> getClasses() throws URISyntaxException
    {
        File file = new File(this.getClass().getProtectionDomain().getCodeSource().getLocation().toURI().getPath());
       
        try
        {
            @SuppressWarnings("resource")
            JarFile jar = new JarFile(file);
          
            for (Enumeration<JarEntry> entry = jar.entries(); entry.hasMoreElements();)
            {
                JarEntry e = entry.nextElement();
                String name = e.getName().replace("/", ".");
              
                if (name.endsWith(".class"))
                {
                    name = name.split(".class")[0];
                    try{
                        Class<?> c = Class.forName(name);
                        if (MobSpell.class.isAssignableFrom(c)){
                            try {
                                Class<? extends MobSpell> mc = (Class<? extends MobSpell>) c;
                                mobSpellClasses.add(mc.newInstance());
                                System.out.println(name);
                                System.out.println("added");
                            } catch (InstantiationException ie) {
                                // TODO Auto-generated catch block
                                ie.printStackTrace();
                            } catch (IllegalAccessException ie) {
                                // TODO Auto-generated catch block
                                ie.printStackTrace();
                            }
                        }
                    } catch (ExceptionInInitializerError ie){
                        ie.printStackTrace();
                    }
                }
            }
        }
        catch (Exception e)
        {
            e.printStackTrace();
        }
        return mobSpellClasses;
    }

 

@mine2012craft
check if the super class is not null and if it's equal to your class mobSpellClasses.class