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Stateful session beans and JNDI-Lookup in Netbeans 6.8/EJB 3.1 does not work

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posted 14 years ago

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I wanted to test the functionality of a very simple stateful session bean, but nothing works! The JNDI-Lookup does not work as the bean is not found and when I call the bean by Depency-Inection via @EJB annotation the value is not memorized.

The stateful session bean:

In the above bean, the variable "memory" should retain its value when called from the same browser, eg. by browser refresh.

The client is programmed with @EJB dependency inection. The variable state of memory is lost.

I marked the JNDI-Lookup bold. This results in a javax.naming.NamingExdeption: Lookup failed for...
I opened an error no 181367 at netbeans.

package ch.geo.servlet;

import ch.geo.bean.NewSessionBean;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.ejb.EJB;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 *
 * @author admin1
 */
@WebServlet(name="StatefulSessionBeanAufruf", urlPatterns={"/StatefulSessionBeanAufruf"})
public class StatefulSessionBeanAufruf extends HttpServlet {
    @EJB
    private NewSessionBean newSessionBean;
    //[b]NewSessionBean newSessionBean = lookupNewSessionBeanBean();[/b]
    //hier passiert Fehler
   
    /** 
     * Processes requests for both HTTP <code>GET</code> and <code>POST</code> methods.
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        try {
            /* TODO output your page here */
            out.println("<html>");
            out.println("<head>");
            out.println("<title>Servlet StatefulSessionBeanAufruf</title>");  
            out.println("</head>");
            out.println("<body>");
            out.println("<h1>Servlet StatefulSessionBeanAufruf at " + request.getContextPath () + "</h1>");
            out.println(newSessionBean.quadr(4));
            //beim zweiten Durchgang abkommentieren, dann Browser refreshen
            //newSessionBean.setMemory(2);
            out.println("<br />Memorierter Wert: "+newSessionBean.getMemory());
            out.println("</body>");
            out.println("</html>");
           /* */
        } finally { 
            out.close();
        }
    }

// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
    /** 
     * Handles the HTTP <code>GET</code> method.
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        processRequest(request, response);
    }

/** 
     * Handles the HTTP <code>POST</code> method.
     * @param request servlet request
     * @param response servlet response
     * @throws ServletException if a servlet-specific error occurs
     * @throws IOException if an I/O error occurs
     */
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        processRequest(request, response);
    }

/** 
     * Returns a short description of the servlet.
     * @return a String containing servlet description
     */
    @Override
    public String getServletInfo() {
        return "Short description";
    }// </editor-fold>

private NewSessionBean lookupNewSessionBeanBean() {
        try {
            Context c = new InitialContext();
            //return (NewSessionBean) c.lookup("java:global/StatefulEnterpriseSessionBeanTest-war/StatefulEnterpriseSessionBeanTest-ejb/NewSessionBean!ch.geo.bean.NewSessionBean");
       
    [b]  return (NewSessionBean) c.lookup("java:global/StatefulEnterpriseSessionBeanTest-war/StatefulEnterpriseSessionBeanTest-ejb/NewSessionBean!ch.geo.bean.NewSessionBean");[/b]

} catch (NamingException ne) {
            System.out.println("Bohne nicht gefunden");
            Logger.getLogger(getClass().getName()).log(Level.SEVERE, "exception caught", ne);
            throw new RuntimeException(ne);
        }
    }

}

Urgent helb needed!!!

Docendo discimus (we learn by teaching)
SCJP 5 Zertifizierung, Vorbereitungsbuch; SCJP 6 Zertifizierung, Vorbereitungsbuch

Jaikiran Pai

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posted 14 years ago

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Are you trying EJB3.1 or EJB3.0?

With EJB3.0, you can have a nointerface view for a bean:

If you are on EJB3.0, have you specified a remote/local business interface for that bean through xml? If not, you will have to either specify it through @Remote/@Local or use their xml counterparts.

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Terence Gronowski

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Posts: 64

posted 14 years ago

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I use the Netbeans 6.8 Bundle (EJB 3.1, EE6) and want to program a shopping cart example with a stateful session bean.

When I call the bean per injection I reach the bean, but the variable does not retain its value. It has to do something with thread safety:

@EJB
private NewSessionBean newSessionBean;

When I click the JNDI call together (all is done by Netbeans 6.8) there ist an error.

I do not type one line by myself! The following error occurs:

java.lang.RuntimeException: javax.naming.NamingEception: Lookup failed for 'java:global/StatefulAufruf-war/StatefulBeanAufruf-ejb/NewSessionBean!ch.geo.bohne.NewSessionBean

There must be an error in this lookup statement or there is something wrong with the application server.

The lookup string is composed as follows:

java:global [<app-name>]<module-name>/<bean-name>!<fully-qualified-interface-name>

The generated lookup string seems to be correct. The <app-name> is omitted, <module-name> is the -war Archive, the <bean-name> is StatefulBeanAufruf-ejb and the <fully-qualified-interface-name> is ch.geo.bohne.NewSessionBean.

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SCJP 5 Zertifizierung, Vorbereitungsbuch; SCJP 6 Zertifizierung, Vorbereitungsbuch

Ralph Jaus

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Posts: 342

posted 14 years ago

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Hi Terence,

have a look at the examples in EJB 3.1 spec, section 4.4.2. I think the lookup-name should be

java:global/StatefulAufruf-war/NewSessionBean

In my opinion it's a disadvantage of glassfish (compared with JBoss, for example) that not all JNDI bindings are listed by the administration tool. But if you start glassfish with the verbose option (use startserv.bat in windows) then the global JNDI name of the ejb should is printed to the console.

As an alternative to using a global JNDI name you could also choose the classical solution for servlets: Also note: Stateful session beans shouldn't be injected or initialized as instance variable because a servlet can be used in multiple threads.

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Terence Gronowski

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Posts: 64

posted 14 years ago

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Hi Ralph

it works! But there is still something else which is not clear:

I want to show, that a stateful session bean can store variable values across browser calls. In the following example that does not work.

a) I have the stateful session bean, the member variable intMemory should memorize its value.

b) I have a servlet, which sets variable intMemory to 10.

@WebServlet(name="SpeicherServlet", urlPatterns={"/SpeicherServlet"})
public class SpeicherServlet extends HttpServlet {
    NewSessionBean newSessionBean = lookupNewSessionBeanBean();   
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
    throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        PrintWriter out = response.getWriter();
        try {
            /* TODO output your page here */
            out.println("<html>");
            out.println("<head>");
            out.println("<title>Servlet SpeicherServlet</title>");  
            out.println("</head>");
            out.println("<body>");
            out.println("<h1>Servlet SpeicherServlet at " + request.getContextPath () + "</h1>");
            [i]newSessionBean.setIntMemory(10);[/i]
            out.println(newSessionBean.getIntMemory());
            out.println("</body>");
            out.println("</html>");
         
        } finally { 
            out.close();
        }
    }

private NewSessionBean lookupNewSessionBeanBean() {
        try {
            Context c = new InitialContext();
            //return (NewSessionBean) c.lookup("java:global/SessionTest-war/SessionTest-ejb/NewSessionBean!ch.geo.bean.NewSessionBean");
            return (NewSessionBean) c.lookup("java:global/SessionTest-war/NewSessionBean");
        } catch (NamingException ne) {
            Logger.getLogger(getClass().getName()).log(Level.SEVERE, "exception caught", ne);
            throw new RuntimeException(ne);
        }
    }

}

c) I have an identical servlet, who reads the the variable IntMemory: out.println(newSessionBean.getIntMemory());

Now the problem is, that the value set with the first applet ist not stored when I call it with the reading Applet. I used an Integer in case primitive Variables are not serialized. But this does not help.

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SCJP 5 Zertifizierung, Vorbereitungsbuch; SCJP 6 Zertifizierung, Vorbereitungsbuch

Terence Gronowski

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Posts: 64

posted 14 years ago

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Designing a shopping cart with a stateful session bean

I found a solution, but it is very inelegant:

The servlet has alzheimer and does not remember the refernce variable of the stateful session bean after a refresh. So you have to save the reference in a HttpSession variable.

The stateful session Bean in wich the state of intMemory should be preserved:

The client Servlet reads the Value of intMemory and adds 10 to it. If yo do not save the reference to the Bean the value will stay 10. If you uncomment the blocks and comment out

NewSessionBean newSessionBean = lookupNewSessionBeanBean();

it works as expected, the values of the intMemory variables are as expected 10, 20, 30....

package ch.geo.servlet;
import ch.geo.bean.NewSessionBean;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.logging.Level;
import java.util.logging.Logger;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

@WebServlet(name = "SpeicherServlet", urlPatterns = {"/SpeicherServlet"})
public class SpeicherServlet extends HttpServlet {

protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");

/* Save the reference to the StatefulSessionBean in a Session
        *HttpSession session = request.getSession(true);
        *NewSessionBean newSessionBean = (NewSessionBean) session.getAttribute("SessionsBohne");
        *if (newSessionBean == null) {
        *newSessionBean = lookupNewSessionBeanBean();
        *}
         */

NewSessionBean newSessionBean = lookupNewSessionBeanBean();

PrintWriter out = response.getWriter();
        try {
            /* TODO output your page here */
            out.println("<html>");
            out.println("<head>");
            out.println("<title>Servlet SpeicherServlet</title>");
            out.println("</head>");
            out.println("<body>");
            out.println("<h1>Servlet SpeicherServlet at " + request.getContextPath() + "</h1>");
            int zahl = newSessionBean.getIntMemory();
            newSessionBean.setIntMemory(zahl + 10);
            out.println(newSessionBean.getIntMemory());
            out.println("</body>");
            out.println("</html>");
            /* */
        } finally {
            /*
            *session.setAttribute("SessionsBohne", newSessionBean);
             */
            out.close();
        }
    }

//some standard Methods omitted

private NewSessionBean lookupNewSessionBeanBean() {
        try {
            Context c = new InitialContext();
            //wrong call by Netbeans 6.8
            //return (NewSessionBean) c.lookup("java:global/SessionTest-war/SessionTest-ejb/NewSessionBean!ch.geo.bean.NewSessionBean");
            return (NewSessionBean) c.lookup("java:global/SessionTest-war/NewSessionBean");
        } catch (NamingException ne) {
            Logger.getLogger(getClass().getName()).log(Level.SEVERE, "exception caught", ne);
            throw new RuntimeException(ne);
        }
    }
}

It ist still not time to

First: Suppose I have 2 catalogs with goods and one cart (which is the stateful session bean). If the reference to the stateful session bean is unique, it would not be possible to save values from two catalogs (i.e. servlet clients) to the one single bean. The shop could have only one catalog or the reference has to be promoted to another catalog, i.e. in a session

Second: The above solution where the reference variable of the stateful session bean is saved in a HttpSession seems inelegant, somebody knows a better solution?

Third: Can the variable intMemory be an int instead an Integer and still be preserved? (you usually can only save Objects in a session, but here an int is a compound of an object, I will try and report).

Docendo discimus (we learn by teaching)
SCJP 5 Zertifizierung, Vorbereitungsbuch; SCJP 6 Zertifizierung, Vorbereitungsbuch

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