Question

I’m using JBoss6.1.Final, JSF 2.0 (Mojarra), Weld CDI, MyFaces CODI 1.0.5 (for view-access-scoped)

I’m using something like the Gateway Pattern from Real World Java EE Patterns Rethinking Best Practices (unfortunately I don’t have it with me, so I may have screwed something up here). Basically, the application allows a user to go into “edit mode” and edit a List of people (create, edit, remove) maintained in a @ViewAccessScoped backing bean with an extended persistence context and then click a “save” command link that flushes all their changes to the database. At first I was having a problem with ViewExpiredExceptions (if the browser was idle past the session-timeout period and then further requests are performed), but I added some jQuery to make a get request to a servlet that keeps the session alive (called 10 seconds before session-timeout). This seems to be working but now I have another problem, the backing bean is also a SFSB and after some idle time, it is being removed resulting in the following error message being logged (and all ajax rendered data disappears) when I attempt to perform more edits …

13:06:22,063 SEVERE [javax.enterprise.resource.webcontainer.jsf.context] javax.el.ELException: /index.xhtml @27,81 rendered=”#{!conversationBean.editMode}”: javax.ejb.NoSuchEJBException: Could not find stateful bean: 43h1h2f-9c7qkb-h34t0f34-1-h34teo9p-de

Any ideas on how I could prevent SFSB removal or at least handle it more gracefully?

Here’s my backing bean:

package com.ray.named;

import java.io.Serializable;
import java.util.List;

import javax.annotation.PostConstruct;
import javax.ejb.EJBTransactionRolledbackException;
import javax.ejb.Stateful;
import javax.ejb.TransactionAttribute;
import javax.inject.Named;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.PersistenceContextType;

import org.apache.myfaces.extensions.cdi.core.api.scope.conversation.ViewAccessScoped;

import com.ray.model.Person;

@Named
@Stateful
@ViewAccessScoped
@TransactionAttribute(javax.ejb.TransactionAttributeType.NEVER)
public class ConversationBean implements Serializable {
  private static final long serialVersionUID = 1L;
  //properties
  private List<Person> people;
  private String name;
  private Boolean editMode;

  @PersistenceContext(type=PersistenceContextType.EXTENDED)
  private EntityManager em;

  @PostConstruct
  public void init() {
    people = em.createNamedQuery("Person.findAll", Person.class).getResultList();
    setEditMode(false);
  }

  //event listeners
  public void beginEdits() {
    setEditMode(true);
  }

  public void addPerson() {
    Person p = new Person(name);
    em.persist(p);
    people.add(p);
    name = null;
  }

  public void removePerson(Person p) {
    people.remove(people.indexOf(p));
    em.remove(p);
  }

  //this method flushes the persistence context to the database
  @TransactionAttribute(javax.ejb.TransactionAttributeType.REQUIRES_NEW)
  public void saveEdits() {
    setEditMode(false);
  }

  //getters/setters
  public List<Person> getPeople() {
    return people;
  }

  public String getName() {
    return name;
  }

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

  public Boolean getEditMode() {
    return editMode;
  }

  public void setEditMode(Boolean editMode) {
    this.editMode = editMode;
  }
}

Here’s the Person entity bean:

package com.ray.model;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Version;

@Entity
@NamedQueries({
  @NamedQuery(name="Person.findAll",
              query="SELECT p FROM Person p")
})
public class Person {
  @Id @GeneratedValue(strategy=GenerationType.IDENTITY) 
  private Integer id;
  private String name;
  @Version
  private int version;

  public Person() { }

  public Person(String name) {
    setName(name);
  }

  public boolean equals(Object o) {
    if (!(o instanceof Person)) {
      return false;
    }
    return id == ((Person)o).id;
  }

  //getters/setters
  public String getName() {
    return name;
  }
  public void setName(String name) {
    this.name = name;
  }

  public Integer getId() {
    return id;
  }

  public int getVersion() {
    return version;
  }

  public void setVersion(int version) {
    this.version = version;
  }
}

Here’s the view:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml"
      xmlns:h="http://java.sun.com/jsf/html"
      xmlns:f="http://java.sun.com/jsf/core"
      xmlns:ui="http://java.sun.com/jsf/facelets">
<h:head>
  <script src="http://code.jquery.com/jquery-latest.min.js"></script>
  <script>
  $(document).ready(function() {
    setInterval(function() {
      $.get("#{request.contextPath}/poll");
    }, #{(session.maxInactiveInterval - 10) * 1000});
  });
  </script>
  <title>Conversation Test</title>
</h:head>
<h:body>
  <h:form>
    <h:commandLink value="Begin Edits" rendered="#{!conversationBean.editMode}">
      <f:ajax render="@form" listener="#{conversationBean.beginEdits}"/>
    </h:commandLink>
    <h:commandLink value="Save" rendered="#{conversationBean.editMode}">
      <f:ajax render="@form" listener="#{conversationBean.saveEdits}"/>
    </h:commandLink>
    <h:dataTable id="peopleTable" value="#{conversationBean.people}" var="person">
      <h:column>
        <f:facet name="header">Name</f:facet>
        <h:panelGroup>
          <h:inputText value="#{person.name}" disabled="#{!conversationBean.editMode}">
            <f:ajax/>
          </h:inputText>
          <h:commandLink value="X" disabled="#{!conversationBean.editMode}">
            <f:ajax render="@form" listener="#{conversationBean.removePerson(person)}"/>
          </h:commandLink>
        </h:panelGroup>
      </h:column>
    </h:dataTable>
    <h:panelGrid columns="2">
      <h:outputLabel for="name">Name:</h:outputLabel>
      <h:inputText id="name" value="#{conversationBean.name}" disabled="#{!conversationBean.editMode}"/>
    </h:panelGrid>
    <h:commandButton value="Add" disabled="#{!conversationBean.editMode}">
      <f:ajax execute="@form" render="@form" listener="#{conversationBean.addPerson}"/>
    </h:commandButton>
  </h:form>
</h:body>
</html>

Here’s a servlet used to keep the session alive (called by jQuery ajax get request 10 seconds before session expires):

package com.ray.web;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class PollServlet extends HttpServlet {
  private static final long serialVersionUID = 1L;

  public void init() throws ServletException {
  }

  public String getServletInfo() {
    return null;
  }

  public void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
    request.getSession(); //Keep session alive
  }

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

  public void destroy() {
  }
}

Answer 1

Any ideas on how I could prevent SFSB removal or at least handle it
more gracefully?

To investigate further I would recommend to take a look at the EJB lifecycle hooks for passivation and add some debug output there.

Should that be the source of the problem you will be able to configure / deactivate passivation – but scalability might come up as an issue.

Honestly, this scenario seems quite uncommon to me. In general I would expect requests / conversations / sessions to be working more or less in the default boundaries – should you find yourself writing code that circumvents this can it be that you are better off with a RESTful / stateless approach…?

Please update the question with further information if available.