Session bean question

I am very new to java and I am learning struts using websphere.
I have a bean that I want to make available as a session bean so I don't have to run my query to populate the bean everytime I need the data. I have never done this before and would like to know how.
In my first action after creating the bean I did this to try to make it a session bean
HttpSession session = request.getSession();
UserBean ub = (UserBean) session;
is this right?
Also if I want to use this session bean in other actions do I need to have getters and setters for the bean in the new actions action form?
Also how do I call / invoke the data out of this bean in the other action?

I think you are trying to mix 3 things together: EJB session bean, HttpSession, and JavaBeans. Your UserBean seems like a JavaBean. The above three are totally independent of each other.
JavaEE tutorial may be of help:
http://java.sun.com/javaee/5/docs/tutorial/doc/

Similar Messages

General Design With Database and Session Bean Question

I have an application I am developing where users connect to individual databases located on a server. When they login an admin table is accessed which shows what databases they have permissions to. I am then storing the connection to the database in a backing bean. Hoping to use this connection throughout the session. Is this a good practice to have a users connection left open over the session? I can't create a database pool for each individual database and each user for that database.
If I can store that database connection in a session bean. How do I access that connection from another bean. Or from another java class? I am using Glassfish for my application server with JSF1.2. I have looked at resource injection but have not had any luck with sharing the session bean information.
Sorry if this is a trivial question. I have been a Java developer for years. But just starting developing webapps using JSF.
Thanks

JuCobb2 wrote:
I am then storing the connection to the database in a backing bean. Hoping to use this connection throughout the session. Is this a good practice to have a users connection left open over the session? No it is not. Why should you do so? Always keep the lifetime of connection, statement and resultset as short as possible.

EJB 3.0 Session Bean question

Hi there,
How'd I expose a method of Stateless Session Bean in EJB 3.0? I don't seem to find any annotation for that.
Thanks in advance.
Saeed

If you need to expose method implemented in Session bean, you can invoke the method call from within another method called in Client.
This method has to be defined in the remote interface . The method you are trying to invoke can be defined somewhere else but called in your bean class from within the method definedin the remote interface.

Stateful Session Bean Question

I have a stateful session bean being invoked by my web tier on several request/response transactions. What would be the best way to locate the same session bean ? Would that be the create method in the Home i/f or would i need to supply a finder method for locating an existing bean?

Hi,
Store HomeObject or EJB Object in the Session in the WebTier.
Anil

EJB (Session Beans question)

I use a statefull session bean to validate a user within my servlet, now I want to use that session bean in the jsp page that is next step after the servlet. How can I retrieve that bean on my jsp page?

Try this in your JSP,
<%!
String url = "t3://localhost:7001";
public Context getInitialContext() throws Exception {
    Properties p = new Properties();
    p.put(Context.INITIAL_CONTEXT_FACTORY,
          "Your_Server's Context_Factory");
          //It is "weblogic.jndi.WLInitialContextFactory" for Weblogic.
    p.put(Context.PROVIDER_URL, url);
    return new InitialContext(p);
%>
<%
try {
    Context ctx = getInitialContext();
    BeanHome home = (BeanHome) ctx.lookup("package_if_any.BeanHome" or "Bind_Name_that_you_have_used");
    //Do further operations
%>Hope this helps.,
Sudha

What role can ejb Session Beans play jsp session tracking

          I am also looking for a way to use JSP as ejb client with WLS5.1. i would appreciate any help.
          -Girish
          Prasad Peddada <[email protected]> wrote:
          >David,
          >     The beans which are refered in jsp specs are java beans and not EJB.
          >
          >Prasad
          >
          >David Levy wrote:
          >>
          >> Hello,
          >>
          >> We are using Jsp/Servlets which will hold session state and subsequently
          >> call ejb Session Beans for transaction/persistence coordination . We are
          >> not sure if we are using the correct techniques to control object memory.
          >>
          >> Summary of what we have:
          >>
          >> A jsp with the "useBean" directive:
          >> <jsp:useBean id="MySession" class="com....MySession"
          >> scope="session"></jsp:useBean>
          >>
          >> The class MySession holds other classes ( all serializable).
          >> The class MySession is NOT an ejb Session Bean
          >>
          >> Questions:
          >> We are considering making class MySession an ejb Session Bean so (via it's
          >> passivate/activate feature) we can control instances in memory as more web
          >> clients start the session from the jsp page. I.E. all web clients will have
          >> their own HttpSession instance which holds on to an ejb Session Bean object
          >> "MySession"( or a passivated representation of it)
          >>
          >> 1) Is this a sufficient approach or will there be other memory concerns?
          >> I.E. What about all the HttpSession objects out there? Do they need to be
          >> passivated as well?
          >>
          >> 2) If its a good idea to passivate the HttpSessions as well, then what
          >> mechanism should be used ( servlet session persistence)? Also, if we are
          >> passivating the HttpSession (which holds on to the MySession object graph)
          >> , then why bother with the SessionBean for passivation
          >>
          >> 3) Currently, we only have a single instance of a servlet handling all
          >> requests. Will multiple instances buy us anything?
          >>
          >> 4) How does clustering relate to this topic?
          >>
          >> 5) Can we change the "jsp:useBean" directive so MySession is an ejb Session
          >> Bean or do we have to do the "home.create()" within a jsp script?
          >>
          >> thanks,
          >> dave

EJB question: How to use abstract class in writing a session bean?

I had written an abstract class which implements the session bean as follow:
public abstract class LoggingSessionBean implements SessionBean {
protected SessionContext ctx;
protected abstract Object editRecord(Object obj) throws Exception;
public LoggingSessionBean()
super();
private final String getBeforeUpdateImage(Object obj) throws Exception {
// implement the details of extracting the backup image ...
public void setSessionContext(SessionContext ctx)
this.ctx = ctx;
private final void writeThisImageToDatabase(String aStr) {
// connect to database to write the record ...
public final Object update(final Object obj) {
try {
final String aStr = getBeforeUpdateImage(obj);
writeThisImageToDatabase(aStr);
editRecord(obj);
} catch (Exception e) {
ctx.setRollbackOnly();
This abstract class is to write the backup image to the database so that other session beans extending it only need to implement the details in editRecord(Object Obj) and they do not need to take care of the operation of making the backup image.
However, some several questions for me are:
1. If I write a class ScheduleSessionBean extending the above abstract class and the according 2 interfaces ScheduleSession and ScheduleSessionHome for this session bean (void update(Object obj); defined in ScheduleSession), do I still need to write the interfaces for LoggingSession and LoggingSessionHome?
2. If I wrote the interface LoggingSession extending EJBObject where it defined the abstract methods "void update(Object obj);" and "void setSessionContext(SessionContext ctx);", that this meant I needed to write the ScheduleSession to implement the Logging Session?
3. I used OC4J 9.0.4. How can I define the ejb-jar.xml in this case?

Hi Maggie,
1. do I still need to write
the interfaces for LoggingSession and
LoggingSessionHome?"LoggingSessionBean" can't be a session bean, because it's an abstract class. Therefore there's no point in thinking about the 'home' and 'remote' interfaces.
2. this
meant I needed to write the ScheduleSession to
implement the Logging Session?Again, not really a question worth considering, since "LoggingSessionBean" can't be an EJB.
3. I used OC4J 9.0.4. How can I define the
ejb-jar.xml in this case?Same as you define it for any version of OC4J and for any EJB container, for that matter, since the "ejb-jar.xml" file is defined by the EJB specification.
Let me suggest that you create a "Logging" class as a regular java class, and give your "ScheduleSessionBean" a member that is an instance of the "Logging" class.
Alternatively, the "ScheduleSessionBean" can extend the "Logging" class and implement the "SessionBean" interface.
Good Luck,
Avi.

Stateless Session Bean + EJB Question + Jboss

Hello,
If I have a stateless session bean on a linux machine and it works locally what do i need to do to access a method in the session bean from a remote windows machine.
I would like to be able to execute my client jar file on a windows machine and have it access the jboss server on the linux machine. what do i need to do?
i have the session bean working locally on both windows and linux machine. do i need to to have a JSP/Servlet to access the session bean? can the session bean not be accessed directly? what should my classpath look like? do I need to include extra jar files in my client jar file.?
Thanks,
Joyce

Thanks guys for the help but I am still a little lost.
My Client windows machine has the client jar file and all the other jar files. This is my client class
package helloworld.client;
import javax.naming.Context;
import javax.naming.InitialContext;
import java.util.Hashtable;
import java.util.Properties;
import helloworld.interfaces.HelloWorldHome;
import helloworld.interfaces.HelloWorld;
public class HelloClient
     public static void main(String[] args)
          Hashtable prop = new Hashtable();
          prop.put ("java.naming.factory.url.pkgs","org.jboss.naming:org.jnp.interfaces");
          prop.put ("java.naming.provider.url","jnp://172.16.220.160:1099");
          prop.put ("java.naming.factory.initial","org.jnp.interfaces.NamingContextFactory");
          try
               Context ctx = new InitialContext(prop);
               Object obj = ctx.lookup("ejb/helloworld/HelloWorld");
               System.out.println(obj);
               HelloWorldHome home = (HelloWorldHome)javax.rmi.PortableRemoteObject.narrow(obj, HelloWorldHome.class);
               HelloWorld helloWorld = home.create();
               String str = helloWorld.sayHelloEJB("JOYCE is COOL");
               System.out.println(str);
               helloWorld.remove();
          catch(Exception e)
               e.printStackTrace();
I get a NullPointer ie the home object is null. The IP address is the IP of the Linux machine that has Jboss running on.
Questions are:
1. Do I need to have Tomcat running on my client machine if I am to connect via HTTP? Does this alter my client code.?
2. My JNDI lookup is what is causing the problem. Does my jboss.xml and my ejb-jar.jar look okay to you.
jboss.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE jboss PUBLIC "-//JBoss//DTD JBOSS//EN" "http://www.jboss.org/j2ee/dtd/jboss.dtd">
<jboss>
<enterprise-beans>
<session>
<ejb-name>helloworld/HelloWorld</ejb-name>
<jndi-name>ejb/helloworld/HelloWorld</jndi-name>
</session>
</enterprise-beans>
<resource-managers>
</resource-managers>
</jboss>
ejb-jar.jar
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE ejb-jar PUBLIC "-//Sun Microsystems, Inc.//DTD Enterprise JavaBeans 2.0//EN" "http://java.sun.com/dtd/ejb-jar_2_0.dtd">
<ejb-jar >
<description>No Description.</description>
<display-name>Generated by XDoclet</display-name>
<enterprise-beans>

<session >
<description><![CDATA[No Description.]]></description>
<ejb-name>helloworld/HelloWorld</ejb-name>
<home>helloworld.interfaces.HelloWorldHome</home>
<remote>helloworld.interfaces.HelloWorld</remote>
<ejb-class>helloworld.session.HelloWorldBean</ejb-class>
<session-type>Stateless</session-type>
<transaction-type>Bean</transaction-type>
</session>





</enterprise-beans>


<assembly-descriptor >



</assembly-descriptor>
</ejb-jar>
Do I need RMI ? Do I need to concern myself with CORBA? All Im looking for is a step by step to understanding what I need to configure? Is their some way I can debug?
Thanks alot,
Joyce

EJB: Stateless Session Bean create() Question.

Lets say I have a stateless session bean that fetches data from my database. The point of the bean is to just do large SQL searches and funnel data back to the client. The prolem I have is that I am somehow fighting memory leaks. Despite having checked the code a number of times, the memory usage on my appserver continues to climb no matter what I do. I have theorized that the problem might be in the way Im using ma DataFetchBean (DFB).
When I start the client, he obtains a user session. This is a stateful session bean that he uses for almost all communication with the server. Then I call "getDataFetchBean" in the user session which calls DataFetchBeanHome.create(). Then the client holds onto the returned reference, using it for the live of his connection. As he disconnects, he calls remove on the bean.
Question is this:
1) Is it better for me to call create() prior to each call to the stateless session bean ?
2) Do you have any theories on why im loosing memory with this setup?
TIA
-- Rob

1. But I thought you were using a 'stateful session bean'?
2. For stateless session beans, there is no direct link between a remote reference and an instance of the bean. It is safe to hang on to the remote reference as long as you would like, of course it may go stale if the server dies. You will also find that the create() method does not actually contact the server, so doing it each usage costs very little. So, either way you should be fine.
3. As for memory leaks, make sure that you are closing all statements, result sets, etc. promptly. These are commonly the problem. Also, use hprof or some other profile tool to determine what types of data you are allocating and (with better tools) what types of data you may be holding on to references to.
Chuck

A tough one for EJB experts - Stateless session bean spec question

I am busy learning more about EJBs and came across something confusing regarding the legal operations in the various container callback methods for stateless session beans.
Specifically, the EJB spec states that in the ejbCreate() method, the SessionContext can be used to obtain a reference to the EJB Object. Now this makes perfect sense with stateful session beans, since the ejbCreate() method isn't called until a client is creating a bean and the container has linked that bean to the client's EJB Object. However, it is my understanding that when it comes to stateless session beans, the container creates the beans and adds them to the bean pool at its leisure. It is not until a business method is called by a client that a stateless bean is actually linked to an EJB object. So, how is it that a stateless bean could ever obtain a reference to an EJB Object from within ejbCreate(). Which EJB Object would it be linked to? This operation just doesn't appear to make sense in that context.
Can anyone clarify this for me?

Interesting question. I have such questions all the time! Here's a link to a similar discussion
http://saloon.javaranch.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic&f=70&t=000905
Also, I tried this using Weblogic 8.1. Tried to access the EJBObject in ejbCreate before any business method was invoked. I did this by specifying a value for initial-beans-in-free-pool and found that the hash code for the EJBObject was the same for all the bean instances that were created on startup.
I then invoked a business method and accessed the EJBObject in that method. Again the hash code for the object was the same as the one created on startup.
Seemed to be that there is a 1:n relation between the EJBObject and bean instances.
This may be container specific. The spec says the user should be able to invoke the getEJBObject() method in ejbCreate(), its upto the container to comply with it.

A question about entity manager in stateless session bean.

JSR 220 ejbcore, page 47 : stateless session bean: All business object references of the same interface type for the same stateless session bean have the "same object identity", which is assigned by the container.
So, if we have two session beans in client code...
@EJB Cart cart1;
@EJB Cart cart2;
then cart1.equals(cart2)==true
If we declare entity manager in stateless session bean:
@PersistenceContext( unitName="ds" ,type=PersistenceContextType.TRANSACTION)
private EntityManager em;If cart1 and cart2 are the same reference, do we have any problem when using the same reference(maybe the same em? ) to get data from db?

If cart1 and cart2 are the same reference, do we have
any problem when using the same reference(maybe the
same em? ) to get data from db?No. In EJB, there is a distinction between the EJB reference and the bean instance.
Each time you make an invocation on an EJB reference for a stateless session bean,
the container can choose any instance of that bean's bean class to process the
invocation. That's true whether you invoke the same reference multiple times or
two difference references to the same bean.
Each bean instance is guaranteed to be single-threaded.

Java.io in J2ee stateless session bean, general questions about debugging

Doing conventional Java IO (with java.io functions and classes such as
PrintWriter and println) in a Enterprise bean has been discussed before
in this and other forum. We know that the EJB specification says not to do it.
(For example the EJB 2.0 spec, 24.1.2) says that an enterprise
bean must not use the java.io package to attempt to access files and
directories int he file system."
The discussion in various forums including this one is that
a) using java.io in a bean would impact portability, ability to
move the bean for load balancing
b) However, this is not always an an issue and it may be reasonable
to use these functions anyway. e. g. see the response by "maozhoulu"
on Jun 21, 2002.
I tried it in Sun Application Server Nine in my stateless Session Bean:
package RS;
import RS.CourseHome;
import RS.CoursePK;
import java.rmi.RemoteException;
import javax.naming.InitialContext;
import javax.naming.Context;
import javax.rmi.PortableRemoteObject;
import javax.ejb.EJBException;
import java.io.*;
public class AddCourseBean implements javax.ejb.SessionBean {
   public void ejbCreate(){};
   public void CreateCourse (int CourseNumber, String CourseName) {
    try {
     System.out.println("in Create Course");
     PrintWriter F = null;
     try {
      F = new PrintWriter (new FileOutputStream("/tmp/v/af"));
     catch (java.io.FileNotFoundException fe){}
     F.println ("here zero");F.flush();
     InitialContext jndiContext = new InitialContext();
     F.println ("here one");F.flush();
     Object o = jndiContext.lookup("ejb/X");
         ...I got a Null pointer exception on the line:
"F.println("here zero"); Is there anyway one can do simple debugging with print lines in one's beans?
Or is there something obviousthat I am overlooking? (I saw mention of doing
debugging with System.out.println but to where would the bean write?)
I tried using the Jakarta Commons Logging, but I got a
java.lang.NoClassDefFoundError on org/apache/commons/logging/LogFactory
Which logging system does one use in GlassFish, hopefully one with minimal
configuration? I want to do some debugging, not set up logging for a full
enterprise system.
Thanks for your insight and advice.
Dr. Laurence Leff, Associate Professor of Computer Science WIU ST447 61455
Pager 309 367 0787, Fax 309 298 2302

My apology for posting this message twice. I looked for it before and
did not see it. I thought I forget to click the "Post message" button.
Also, I did resolve one problem. System.out.println does go to
the log file, which in my case turned out to be:
/opt/j2ee/SUNWappserver/domains/domain1/logs/server.log
(Obvously, the first part would vary based upon where you installed your
Application Server Nine.)
However, it would be nice if there was some way to use FILE I/O inside of
beans. I am teaching some J2EE in the graduate software engineering course,
and I believe this would be pedagogically sound even if other techniques
would be appropriate for a production environment.
Thanks for your patience with this problem and my duplicate post.

Question about the Create Session Bean Wizard

Hi,
I'm using the Session Bean Wizard to generate a session facade in EJB 3.0. In step 2 «choose methods to expose through this facade», I only see 2 methods generated for each entity: findAll and remove.
When I click Help on this page, the documentation specify the following:
«Use the tree control to specify the core methods and entity methods you want to generate. Core Facade Methods Theese methods are used for basic CRUD (create, read, update, delete) functionality. »
So why is the wizard only offering to generate findAll and remove?
Also the remove method generated does not seem to delete anything as in the following :
public void removeDcaRole(DcaRole dcaRole) {
final EntityManager em = getEntityManager();
try {
final EntityTransaction et = em.getTransaction();
try {
et.begin();
dcaRole = em.find(DcaRole.class, new DcaRolePK(dcaRole.getDcaNo(), dcaRole.getTRoleCode()));
et.commit(); // where is the delete ???
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if (et != null && et.isActive()) {
et.rollback();
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if (em != null && em.isOpen()) {
em.close();
Can I use the remove method as a starting point to an update ?
Any comment on this would be appreciated.

There are update and insert methods under the "core" section/
See this image : http://www.oracle.com/technology/obe/obe1013jdev/10131/10131_ejb_30/images/b20105.gif
You might want to follow this tutorial to see how it works:
http://www.oracle.com/technology/obe/obe1013jdev/10131/10131_ejb_30/ejb_30.htm#t4

Newbie question: Can't see session bean in business operations after deployment

Hi,
I've just deployed a session bean (using WLS 7.0) sucessfully, but I can't see
the deployed EJB in the business operations in studio. Am I suppose to update
something on the integrator side that references the EJB? Or is there something
else? Any help would be greatly appreciated.
Thanks
Aashish

Hi,
Sorry, but I don't know what you mean.
Could you explain it more detailed, please?
I see following, when start integrator.bat:
[code]
Developer 4.7 Build 999
Exception in thread "Thread-3" java.lang.NullPointerException
        at com.wm.app.b2b.dev.DevConnectDialog.itemStateChanged(DevConnectDialog.java:253)
        at javax.swing.JComboBox.fireItemStateChanged(Unknown Source)
        at javax.swing.JComboBox.selectedItemChanged(Unknown Source)
        at javax.swing.JComboBox.contentsChanged(Unknown Source)
        at javax.swing.AbstractListModel.fireContentsChanged(Unknown Source)
        at javax.swing.DefaultComboBoxModel.setSelectedItem(Unknown Source)
        at javax.swing.JComboBox.setSelectedItem(Unknown Source)
        at com.wm.app.b2b.dev.DevConnectDialog.<init>(DevConnectDialog.java:210)
        at com.wm.app.b2b.dev.DevMainFrame.doConnect(DevMainFrame.java:759)
        at com.wm.app.b2b.dev.DevMain$1.run(DevMain.java:195)
        at java.lang.Thread.run(Unknown Source)
        at com.wm.ui.UiFrame$7.run(UiFrame.java:344)
[/code]
Thanks.

EJB 3.0 - Communicate an Applet with a Session Bean

Hello
I'm developing an EJB 3.0 app (eclipse and glassfish tools bundle), and I have an applet that has to use remote session beans.
QUESTION: Is it possible for the applet to connect to EJB?
QUESTION: By creating a J2EE application client project, can I use @EJB annotations to inject the session bean directly to the applet, avoiding the JNDI lookup?
(since I imagine that the anwser to the second one is NO, I do the following consideration)
Given an application client project, I imagine that this application can run remotely on a client machine/JRE. Then this application can use Annotations/injection facilities whenever it runs on a J2EE client container (which I assume consists of a set of libraries provided by the application server vendor, Glassfish in that case). Could this application be deployed using Java Web Start? If so, why can't it be deployed as an applet? (both options run in a client JRE, don't they?).
QUESTION: In either case (applet or JWS), how do I have to package the JAR file (using Eclipse) so that it contains the needed libraries for accessing the EJB? Which are those libraries?
At the time being, I'm trying to implement a sample application that follows the "Applet doing JNDI lookup" approach. I have:
- an EAR project
- an EJB project (containing an Entity Bean and a Stateless Session Bean with a @Remote interface)
@Remote
public interface HelloRemote {
     public String hello(String name);
@Stateless
public class Hello implements HelloRemote {
     @Override
     public String hello(String name) {
          return "Hello "+name+"!!";
}- an Application Client project (containing the applet code):
public class ClientApplet extends JApplet {
     public void init(){
          try {
               Context jndiContext = getInitialContext( );
               HelloRemote server = (HelloRemote) jndiContext.lookup(HelloRemote.class.getName());
               setContentPane(new JLabel(server.hello("Gerard")));
          } catch (NamingException e) {
               // TODO Auto-generated catch block
               e.printStackTrace();
     private Context getInitialContext() throws NamingException{
          Properties props = new Properties();
          props.setProperty("java.naming.factory.initial", "com.sun.enterprise.naming.SerialInitContextFactory");
          props.setProperty("org.omg.CORBA.ORBInitialHost", "myhost");
          props.setProperty("org.omg.CORBA.ORBInitialPort", "3700");
          return new InitialContext(props);
}- a static web project (with a sample web page that contains the applet object the corresponding applet JAR file)
I tried to export the Application Client project as an "application client JAR", in the hope that the java EE libraries bundled with glassfish (listed as libraries of this project) would be packaged too.
No success, so now I'll try to copy all the JAR files (one by one) into the +\WebContent\+ folder of the Web Project, and add references to each of them in the archive="" attribute of the +<applet>+ HTML tag. Although this might work, I suspect that I am missing the good/easy way of doing it. Any suggestions?
Thanks in advance,
Gerard
Edited by: gsoldevila on May 6, 2009 7:09 AM

An Applet can communicate with an EJB via JNDI lookup but I would (personally) use an intermediate Servlet to handle this. Client to Servlet communication is http whereas to ejb is iiop - which might be blocked.
Injection only works in managed classes (EJB, Servlet, Listeners..) and an Application Client main class. So yes you could use an app client for handling resource injection.
m

Session bean question

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