Why can't I send Serializable Object with ObjectOutputStream in Java?

Question

I want to send an object with ObjectOutputStream in Java. I have a class named TicketList.

Here is my class:

public class TicketList implements Serializable{

    private ArrayList<Ticket> ticketlist; 


    //Konstruktor: Erstellt eine Liste mit einerm Benutzername
    public TicketList(ArrayList<Ticket> list){
        this.ticketlist = list;
    }

    //Standart Konstruktor
    public TicketList(){
        ticketlist = new ArrayList<>();
    }

    //Fügt der Liste ein neues Element hinzu
    public void addToTicketList(Ticket ticket){
        ticketlist.add(ticket);
    }

    //Gibt die Liste zurück
    public List<Ticket> getTicketList(){
        //Daten werden aus der Datenbank geladen
        return ticketlist; 
    }

    public Ticket getTicketByIndex(int index){
        return ticketlist.get(index);
    }
}

I get this error:

java.io.NotSerializableException: taraticketmodel.Ticket
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1184)
    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
    at java.util.ArrayList.writeObject(ArrayList.java:762)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:988)
    at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1496)
    at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
    at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
    at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
    at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
    at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
    at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
    at taraticketmodel.ClientManager.sendObjectToServer(ClientManager.java:28)
    at taraticketclient.Service.send(Service.java:23)
    at taraticketfrontendtest.MainTest.main(MainTest.java:45)

If I test this with other class it works :(

Answer 1

The class that should implement serializable is the one stored into the ArrayList but not the one used to build the ArrayList.