Beispiel

public void doGet(HttpServletRequest req, HttpServletResponse resp) {

HttpSession session = req.getSession(true);
session.setAttribute(ATTRIB_NAME, new NonSerializableData());
// ...
}
public class NonSerializableData {
// ...
}

private static final String ATTRIB_NAME = "badExample";

Lösung
Lassen Sie entweder 'java.io.Serializable' vom Objekt implementieren, machen Sie das Feld transient, oder speichern Sie das Objekt nicht in 'HttpSession'.

public void doGet(HttpServletRequest req, HttpServletResponse resp) {

HttpSession session = req.getSession(true);
session.setAttribute(ATTRIB_NAME, new SerializableData());
// ...
}
public class NonSerializableData implements java.io.Serializable {
static final long serialVersionUID = -817083988410801866L;
// ...
}

private static final String ATTRIB_NAME = "badExample";