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Classloader and casting, how to?

daniele licitra
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Joined: Apr 08, 2013
Posts: 37

i've implemented the loading procedure has described in http://www.coderanch.com/t/383279/java/java/dynamically-loading-class-file-jar
This procedure works.

I've an abstract class AbstractModule that implement the interface ModuleInterface.
Now, I build some different class, Module1, Module2, ecc that extends AbstractModule.

I use this function to load and instantiate the class:


In the core of the program i use

where modulo is of type AbstractModule.
The problem is in the row signed by the arrow or in the calling of the loader over there, i recive the exception:

SEVERE: java.lang.ClassCastException: com.bss.framework.bssmoduloutenti.ModuloGrafico cannot be cast to com.bss.framework.astratte.AbstractModule
at com.bss.framework.utils.BssLoader.caricaModulo(BssLoader.java:92) <-- this is the arrowed key
at com.bss.framework.servizi.SessioneUtente.setModuloCorrente(SessioneUtente.java:178) <--- this is the calling

How can I solve it? There is something wrong?
Thanks


JPA 2.1.0
Glassfish 3.1->4, Wildfly, Primefaces 3.4->4
Jesper de Jong
Java Cowboy
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Joined: Aug 16, 2005
Posts: 14156
    
  19

First of all, does com.bss.framework.bssmoduloutenti.ModuloGrafico indeed extend com.bss.framework.astratte.AbstractModule?

Furthermore, the problem might be that you load the ModuloGrafico class using another classloader than what AbstractModule was loaded with. I don't know the exact details, but as far as I know classloaders are separated in such a way that a class loaded with one classloader is in a separate space than classes loaded with a different classloader.

It's just a guess and I'm not sure if it will work, but I think it might work if you initialize your URLClassLoader differently, setting the classloader of AbstraceModule as the parent:


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daniele licitra
Ranch Hand

Joined: Apr 08, 2013
Posts: 37

Thank for replying.


i've modified the loader function according to yout reply:


i send the Classloader c from the caller and it works! Thanks a lot
 
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