"ClassCastException" for items in List after serialization

Question

consider this code:
public class MyClass implements Serializable {
  public double price = -1;
  public double volume = -1;
List list = new ArrayList<MyClass>();
while(!endOfData) {
  MyClass mc = new MyClass();
  mc.price = x;
  mc.volume = y;
  list.add(mc);
ObjectOutputStream oos = new ObjectOutputStream(out);
oos.writeObject(list);----
and then the receiver-side:
ObjectInputStream ois = new ObjectInputStream(in);
List list = (List) ois.readObject();
MyClass mc = (MyClass) list.get(2);
..... error ... error ...
Exception in thread "Thread-1" java.lang.ClassCastException: MyClass
note: using a Double instead of MyClass works ok.
also please notice:
ObjectInputStream ois = new ObjectInputStream(in);
List list = (List) ois.readObject();
Object mc = (Object) list.get(4);
System.out.println("this is what i am --> " + mc.getClass().getCanonicalName());
output: "this is what i am --> MyClass"
thanks.
Message was edited by:
suppon

Answer 1

the MyClass objects are not
initially loaded in the receiver's JVM.Make a custom class as:
public class CustomObjectInputStream extends ObjectInputStream {
    private ClassLoader classLoader;
    /** Creates a new instance of CustomObjectInputStream */
    public CustomObjectInputStream(InputStream in, ClassLoader classLoader) throws IOException {
        super(in);
        this.classLoader = classLoader;
    protected Class<?> resolveClass(ObjectStreamClass desc) throws ClassNotFoundException {
        return Class.forName(desc.getName(), false, classLoader);
}and use an instance of this class instead of the standard object inputstream to deserialize your object. You should pass the url class loader as an argument to the constructor of the custom object input stream. The reason is that the standard object inputstream only recognises classes that are "statically defined in the JAVA class path". (I quote the last text because I am not sure if I am using the right terminology, but I hope you understand what I mean.)
why do i get
"ClassCastExceptions" ??
and not
"ClassNotFoundException"
??This must be because somehow you have a "static" class definition for MyClass anyway, otherwise you wouldn't be able to write the following code and have it compile:
MyClass item = (MyClass) class1.cast(list.get(7));Apparently your "static" MyClass definition does not correspond with the MyClass definition in your .jar file.
You can only access a deserialized object of which the class definition is in a .jar file through reflection, unless you can cast it to an interface with a "static" definition.