Question

I have set up a UDP client/server model that can send string messages to each other.

I’ve created a custom class LoginRequest which is serialized and sent to the server containing the username and password. When the getters for these variables are called they return null values even though I check the variables before the LoginRequest is sent.

Here is the code for serializing and sending datagram from the client:

private void login(String name, char[] pass) throws SQLException {
    try {
        LoginRequest login = new LoginRequest(name, pass);
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream(baos);
        oos.writeObject(login);
        byte[] buffer= baos.toByteArray();
        oos.close();
        baos.close();
        DatagramPacket packet =
                new DatagramPacket(buffer, buffer.length, InetAddress.getByName(SERVER), 10110);
        DatagramSocket sSocket = new DatagramSocket();
        sSocket.send(packet);
        login.getUsername();

    } catch (Exception e) {
        e.printStackTrace();
    }
}

Here is the code for de-serializing the LoginRequest and reading the username:

private void readMessage() {
    try {
            ByteArrayInputStream bais = new ByteArrayInputStream(cPacket.getData());
            ObjectInputStream ois = new ObjectInputStream(bais);
            Object obj = ois.readObject();
            bais.close();
            ois.close();
            if(obj instanceof LoginRequest) {
                System.out.println("Login request");
                LoginRequest login = (LoginRequest) obj;
                login.getUsername();
            } else {
                System.out.println("Not a login request");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

Here is the Code for the LoginRequest:

public class LoginRequest implements Serializable {
/**
 * 
 */
private static final long serialVersionUID = -1379800611469143228L;
private static String username;
private static char[] password;

public LoginRequest(String name, char[] pass) {
    username = name;
    password = pass;
}

public String getUsername() {
    System.out.println("Username: " + username);
    return username;
}

public char[] getPassword() {
    String p = password.toString();
    System.out.println("Password: " + p);
    return password;
}
}

When I attempt to read the username or password after this deserialization, I get a NullPointerException. I will be extremely happy if someone can point me in the right direction.

Answer 1

Drop the static on your attribute usename and password!