class cast exception when I tried to covert the class object to specific one

[shanu]

Hi,

In my custom classloader i read the bytes using fileinputstream and constructed a class object using define class method.

then
I have used newInstance method on that loaded class object.
But casting to the specific Object is failing with class cast exception
can any one let me know the reason

regards
shanawaz

[dmjpro]

Hi,

In my custom classloader i read the bytes using fileinputstream and constructed a class object using define class method.

then
I have used newInstance method on that loaded class object.
But casting to the specific Object is failing with class cast exception
can any one let me know the reason

regards
shanawaz

Show me the sample Code.


Debasis Jana

[shanu]

Show me the sample Code.


Debasis Jana

Hi Debasis,

class Loader1 extends ClassLoader{
  public Class findClass(String name) throws ClassNotFoundException{
    System.out.println("in findClass");
    byte[] b=null;
   try{
     b = loadClassData(name);
   }catch(Exception e){
 
   }
   Class c=defineClass("javaexp.PrimeNumber",b,0,b.length);
  // resolveClass(c);
   //        Compiler.compileClass(c);
   try{
     Constructor con=c.getConstructor(new Class[]{});
     System.out.println(con.newInstance(new Object[]{}));
       javaexp.PrimeNumbe ov1=(javaexp.PrimeNumbe)con.newInstance(new Object[]{});//exception comes here
     //javaexp.PrimeNumbe ov = (javaexp.PrimeNumbe) c.newInstance();
   }catch(Exception e){
     e.printStackTrace();
   }
     return c;
  }
 
  private byte[] loadClassData(String name) throws FileNotFoundException{
    System.out.println("in loadClass");
    File f=new File(name);
    FileInputStream fi=new FileInputStream(f);
    BufferedInputStream bi=new BufferedInputStream(fi);
    byte  b[]=null;
    //int b;
    try{
    b=new byte[bi.available()];
    bi.read(b);
    bi.close();
    fi.close();
    }catch(Exception e){
      e.printStackTrace();
    }
 
    return b;
  }
}
 
public class MyClassLoader {
  public MyClassLoader() {
  }
  public static void main(String args[])throws Exception{
    Loader1 l1=new Loader1();
 
    System.out.println("before calling");
    Class c=l1.loadClass("C:/cptbackup/DM/classes/javaexp/PrimeNumber.class");
 
    //Class c=l1.loadClass("javaexp.Override");
    //Class c=Class.forName("javaexp.Override");
    if(c.newInstance() instanceof Class){
      System.out.println("yes");
    }
 
   // Override ov=(Override)c.newInstance();
   //Constructor con=c.getConstructor(new Class[]{});
    //   Object com=(Object)con.newInstance(new Object[]{});
   // javaexp.Override om=(javaexp.Override)ov;
 
   // if(ov instanceof Override){
     // System.out.println("yes");
    //}
 
 
  }
}

Thanks & regards
shanawaz shaik

[BigDaddyLH]

javaexp.PrimeNumbe ov1=(javaexp.PrimeNumbe)con.newInstance(new Object[]{});//exception comes here

What happens if you debug this line? If you do this?

Object object = con.newInstance(new Object[]{});
System.out.println(object.getClass());

[RedSon]

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