My session objects are only stored
within the request scope on google app engine and I can't figure out how to persist objects between requests.
The docs are next to useless on this matter and I can't find anyone who's experienced a similar problem. Please help.
When I store session objects in
the servlet and forward
the request to a JSP using:
getServletContext().getRequestDispatcher("/example.jsp").forward(request,response);
Everything works like it should. But when I store objects to
the session and redirect
the request using:
response.sendRedirect("/example/url");
The session objects are lost to
the ether. In fact when I dump session key/value pairs on new requests there is absolutely nothing, session objects only appear
within the request scope of servlets which create session objects. It appears to me that
the objects are not being written to Memcache or Datastore.
In terms of configuring sessions for my application I have set
<sessions-enabled>true</sessions-enabled>
In appengine-web.xml. Is there anything else I am missing?
The single paragraph of documentation on sessions also notes that only objects which implement Serializable can be stored in
the session between requests. I have included an example of
the code which is not working below.
The obvious solution is to not use redirects, and this might be ok for
the example given below but some application data does need to be stored in
the session between requests so I need to find a solution to this problem.
EXAMPLE:
The class FlashMessage gives feedback to
the user from server-side operations.
if (email.send()) {
FlashMessage flash = new FlashMessage(FlashMessage.SUCCESS, "Your message has been sent.");
session.setAttribute(FlashMessage.SESSION_KEY, flash);
//
The flash message will not be available in
the session object in
the next request
response.sendRedirect(URL.HOME);
} else {
FlashMessage flash = new FlashMessage(FlashMessage.ERROR, FlashMessage.INVALID_FORM_DATA);
session.setAttribute(FlashMessage.SESSION_KEY, flash);
//
The flash message is displayed without problem
getServletContext().getRequestDispatcher(Templates.CONTACT_FORM).forward(request,response);
}
FlashMessage.java
import java.io.Serializable;
public class FlashMessage implements Serializable {
private static final long serialVersionUID = 8109520737272565760L; // I have tried using different, default and no serialVersionUID
public static final String SESSION_KEY = "flashMessage";
public static final String ERROR = "error";
public static final String SUCCESS = "success";
public static final String INVALID_FORM_DATA = "Your request failed to validate.";
private String message;
private String type;
public FlashMessage (String type, String message) {
this.type = type;
this.message = message;
}
public String display(){
return "<div id='flash' class='" + type + "'>" + message + "</div>";
}
}
