Object ArrayList over socket

Question

I have to pass an ArrayList over tcp socket (Server > Client) over the network. When I pass and Arraylist of Strings it works fine and the client is able accept the ArrayList and and print. but when the ArrayList is off Objects I have many exceptions and it does not work. Have a look below please.

Server

    ArrayList<Database> List = new ArrayList<>(); //Database is a seperate class
    Database item1 = new Database();
            item1.code = "1568";
    item1.name = "Round Table";
    item1.details = "Ikeas best Seller";
    item1.inStock = "17";
    List.add(item1);

...

ObjectOutputStream oout = new ObjectOutputStream(socket.getOutputStream());
oout.writeObject(List);

Client

ObjectInputStream iin =  new ObjectInputStream(socket.getInputStream());
Object items = iin.readObject();

Using this code I have many Exceptions thrown. If I replace the array with a string type array like ArrayList<String> Items = new ArrayList<>(); It will work fine. Any Ideas? I am really stack here. Thank You!

Answer 1

The object you are putting in the list and sending must implement the Serializable interface. That also means that fields within that class will also have to be Serializable.