public class TestServlet extends HttpServlet {

  public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
    doPost(request,response);
  }

  public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException {
    response.setContentType("text/html");
    PrintWriter out = response.getWriter();
    HttpSession session = request.getSession();
    Dog d = new Dog();
    d.setName("Peter");
    session.setAttribute("test", d);
    /*Dog d1 = new Dog();
    d1.setName("Adam");
    */
    d.setName("Adam");
    session.setAttribute("test",d);
  }

}

public class MyAttributeListener implements HttpSessionAttributeListener {
  @Override
  public void attributeAdded(HttpSessionBindingEvent httpSessionBindingEvent) {
    System.out.println("Attribute Added");
    String attributeName = httpSessionBindingEvent.getName();
    Dog attributeValue = (Dog) httpSessionBindingEvent.getValue();
    System.out.println("Attribute Added:" + attributeName + ":" + attributeValue.getName());

  }

  @Override
  public void attributeRemoved(HttpSessionBindingEvent httpSessionBindingEvent) {
    String attributeName = httpSessionBindingEvent.getName();
    String attributeValue = (String) httpSessionBindingEvent.getValue();
    System.out.println("Attribute removed:" + attributeName + ":" + attributeValue);


  }

  @Override
  public void attributeReplaced(HttpSessionBindingEvent httpSessionBindingEvent) {
    String attributeName = httpSessionBindingEvent.getName();
    Dog attributeValue = (Dog) httpSessionBindingEvent.getValue();
    System.out.println("Attribute replaced:" + attributeName + ":" + attributeValue.getName());

  }
}

public class Dog  {
  private String name ;

  public String getName() {
    return name;
  }

  public void setName(String name) {
    this.name = name;
  }
}

d.setName("Adam")