Problem calling a method in a servlet witch returns remote ejb

Question

Hi, I have a problem combining servlets ands ejbs, I expose my problem :
What I have :
1 . I have a User table into a SGBD with two attributes login and pass.
2 . I have a UserBean linked to User table with a remote interface
3 . I have a stateless UserSessionBean with a remote interface
4 . I have a UserServlet linked to a jsp page which allows me to add users
5 . I use Jboss
What is working ?
1 - I have a method newUser implemented in my UserSessionBean :
public class UserSessionBean implements SessionBean {
  private SessionContext sessionContext;
  private UserRemoteHome userRemoteHome;
  public void ejbCreate() throws CreateException {
  // Initialize UserRemoteHome
  // Method to add a new user
  public UserRemote newUser(String login, String password) {
        UserRemote newUser = null;
        try {
            newUser = userRemoteHome.create(login, password);
        } catch (RemoteException ex) {
            System.err.println("Error: " + ex);
        } catch (CreateException ex) {
            System.err.println("Error: " + ex);
        return newUser;
}2 - When I test this method with a simple client it works perfectly :
public class TestEJB {
    public static void main(String[] args) {
        Context initialCtx;
        try {
            // Create JNDI context
            // Context initialization
            // Narrow UserSessionHome
            // Create UserSession
            UserSession session = sessionHome.create();
            // Test create
            UserRemote newUser = session.newUser("pierre", "hemici");
            if (newUser != null) {
                System.out.println(newUser.printMe());
        } catch (Exception e) {
            System.err.println("Error: " + e);
            e.printStackTrace();
Result : I got the newUser printed on STDOUT and I check in the User table (in the SGBD) if the new user has been created.
What I want ?
I want to call the newUser method from the UserServlet and use the RemoteUser returned by the method.
What I do ?
The jsp :
1 - I have a jsp page where a get information about the new user to create
2 - I put the login parameter and the password parameter into the request
3 - I call the UserServlet when the button "add" is pressed on the jsp page.
The Servlet :
1 - I have a method doInsert which call the newUser method :
public class UserServlet extends HttpServlet {
    private static final String CONTENT_TYPE = "text/html";
    // EJB Context
    InitialContext ejbCtx;
    // Session bean
    UserSession userSession;
    public void init() throws ServletException {
        try {
            // Open JNDI context (the same as TestClient context)
            // Get UserSession Home
            // Create UserSession
            userSession = userSessionHome.create();
        } catch (NamingException ex) {
            System.out.println("Error: " + ex);
        } catch (RemoteException ex) {
            System.out.println("Error: " + ex);
        } catch (CreateException ex) {
            System.out.println("Error: " + ex);
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws
            ServletException, IOException {
     * Does insertion of the new user in the database.
    public void doInsert(HttpServletRequest req, HttpServletResponse resp) throws
            ServletException, IOException {
        try {
            // Get parameters to create the newUser
            String login = req.getParameter("login");
            String password = req.getParameter("password");
           // Create the newUser
            System.out.println("Calling newUser before");
            UserRemote user = userSession.newUser(login, password);
            System.out.println("Calling newUser after");
        } catch (Exception e) {
    // Clean up resources
    public void destroy() {
Result :
When I run my jsp page and click on the "add" button, I got the message "Calling newUser before" printed in STDOUT and the error message :
ERROR [[userservlet]] Servlet.service() for servlet userservlet threw exception
javax.servlet.ServletException: loader constraints violated when linking javax/ejb/Handle class
     at noumea.user.UserServlet.service(UserServlet.java:112)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:810)
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252)
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
     at org.jboss.web.tomcat.filters.ReplyHeaderFilter.doFilter(ReplyHeaderFilter.java:81)
     at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202)
     at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173)
     at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213)
     at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178)
     at org.jboss.web.tomcat.security.CustomPrincipalValve.invoke(CustomPrincipalValve.java:39)
     at org.jboss.web.tomcat.security.SecurityAssociationValve.invoke(SecurityAssociationValve.java:153)
     at org.jboss.web.tomcat.security.JaccContextValve.invoke(JaccContextValve.java:59)
     at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126)
     at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105)
     at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107)
     at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148)
     at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:856)
     at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:744)
     at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527)
     at org.apache.tomcat.util.net.MasterSlaveWorkerThread.run(MasterSlaveWorkerThread.java:112)
     at java.lang.Thread.run(Thread.java:534)
Constat :
I checked into my SGBD and the new user has been created.
The error appears only when the method return Remote ejbs, if I return simples objects (Strings, int..) it works.
What can I do to resolve this problem ?
Thank you.

Answer 1

"Why do you want to servlet to gain access to another EJB through the stateless session bean. Why cant the servlet call it directly ?"
Because I want to access to the informations included in the entity bean UserBean (which is remote).
You said that it is a bad design, but how can I access to my UserBean ejbs from the session bean if I don't do that ?
For example I want a List of all users to be seen in a jsp page :
1 - I call the method getUserList which returnsan ArrayList of UserRemote.
2 - I iterate over the ArrayList to get the users parameters to be seen.
As the other example (newUser), when I do
ArrayList users = (ArrayList) userSession.getUserList(); with the simple client it works, but in the servlet I got the same error.
But, if I call directly the findAll method (as you'are saying) in the servlet
ArrayList users = (ArrayList) userRemoteHome.findAll(); it works...
I think that if my servlet calls directly entity ejbs, I don't need UserSession bean anymore. Is that right ?
I precise that my design is this :
jsp -> servlet -> session bean -> entity bean -> sgbd
Is that a bad design ? Do I need the session bean anymore ?
Thank you.