Implement my own Class Loader - classloader

Question

I 'm trying to Implement my own Class Loader which is must be transparency for application, And NoClassDefError error still occurs.
here is my Custom Class Loader:
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
public class CustomClassLoader extends ClassLoader{
public CustomClassLoader(ClassLoader parent) {
super(parent);
}
public Class loadClass(String name) throws ClassNotFoundException {
System.out.print(name);
if(!"MyObject".equals(name)){
System.out.println("Super load class function");
return super.loadClass(name);
}
try {
System.out.println("Go to load class function");
String url = "file:C:/Users/ahmad/Desktop/CustomClassLoader/class/MyObject.class";
URL myUrl = new URL(url);
URLConnection connection = myUrl.openConnection();
InputStream input = connection.getInputStream();
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
int data = input.read();
while(data != -1){
buffer.write(data);
data = input.read();
}
input.close();
byte[] classData = buffer.toByteArray();
return defineClass(name, classData, 0, classData.length);
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}
here is my main code:
public class Main {
public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException, InterruptedException{
MyObjectInterface myobj = new MyObject();
System.out.println(myobj.getHelloMessage());
}
}
with -Djava.system.class.loader="CustomClassLoader" parameter for VM.
is there is any thing missed.
Thanks Alot.

Answer 1

You shouldn't use that system property. Try using the loadClass method and reflection Object main = loader.loadClass("Main", true).newInstance(); as suggested here

Answer 2

What is exactly the ClassLoader instance that should be passed into the constructor?
Anyway your implementation is incorrect as you are not delegating to the parent first (which is the way how it works in Java SE).