EntityManager is null

[kgreene]

Hi,

I'm trying to create a class that does database retrieval using entity manager. When I call getVpInfo, I notice that the entity manager is null. I need to access this dao from another class in my app. I am not accessing the dao from the client-side code.

Does anyone know why the entity manager is null. I have also included my persistence.xml

=======

import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

@Stateless
public class VpInfoDAOBean implements VpInfoDAORemote, VpInfoDAOLocal{

@PersistenceContext (unitName="VPInfoDB")
protected EntityManager em;

private static VpInfoDAOBean dao = new VpInfoDAOBean();

public static VpInfoDAOBean getInstance() {return dao;}

public VpInfo getVpInfo(String appGroup)
{
if (em == null)
System.out.println("Vp em is null");
return (VpInfo)em.createQuery(
"from VpInfo v where v.appGroup = :appGroup").setParameter("appGroup", appGroup).getSingleResult();

}




}

================================
persistence.xml


<persistence-unit name="VealMonitorDB">
<jta-data-source>java:/DefaultDS</jta-data-source>

<!--

-->
<!-- -->

</persistence-unit>
<persistence-unit name="VPInfoDB">
<jta-data-source>java:/DefaultDS</jta-data-source>

<!--

-->
<!-- -->

</persistence-unit>

[alrubinger]

How is the calling class accessing an instance of VpInfoDAOBean?

S,
ALR

[kgreene]

Currently, I am using:
VPInfoDAOImpl vpdao = VPInfoDAOImpl.getInstance();

I also tried:

InitialContext ctx = new InitialContext();
VPInfoDAOLocal dao = (VPInfoDAOLocal) ctx.lookup("VPInfoDB/VpInfoDAOBean/local");

I tried VPInfoDAORemote also. That did not work either.

[alrubinger]

VPInfoDAOImpl vpdao = VPInfoDAOImpl.getInstance();

This won't work; here you are constructing a plain object, not accessing an EJB instance from the container.

InitialContext ctx = new InitialContext();
VPInfoDAOLocal dao = (VPInfoDAOLocal) ctx.lookup("VPInfoDB/VpInfoDAOBean/local");

What's not working here? Are you able to perform the lookup, cast, and invoke?

S,
ALR

[kgreene]

When I tried the below, the dao object is null and I cannot call methods on it.

InitialContext ctx = new InitialContext();
VPInfoDAOLocal dao = (VPInfoDAOLocal) ctx.lookup("VPInfoDB/VpInfoDAOBean/local");

[kgreene]

Ok, I am very lost. Forgive me, I am new to jboss and ejbs. I've been looking for a solution for several hours and still have not found the answer. I misspoke about the actual issue. The dao object is not null. I get NameNotFoundException because it can't find it. When I bring up my jndi console it's not there, which is why I'm assuming it can't find it.

I'm calling the lookup from a message-driven bean. I didn't think this is considered client code and didn't think lookup would even work.

If I move the entity manager to the message-driven bean, then it works. However, I get an additional issue in that flush does not commit the updates to the database. I thought perhaps moving the entity manager to a class outside the message-driven bean would solve this issue; however, I have not gotten this to work.

[alrubinger]

Please paste the code that works, the code you'd like to work, and the relevant part of the JNDIView?

S,
ALR

[kgreene]

This code works except for the flush. The flush does not commit the updates to the database. Specifically, I want to update the status in the Fetcher.transfer method. However, the status does not get updated to "RUNNING". It only gets updated to "COMPLETE" once the fetcher is done. I thought maybe moving the entity manager outside the Watcher and Fetcher might fix this issue. So, I created a ConversionFileDAO which I tried to use in the code below, but I get a namenotfoundexception. I of course commented out the em method calls when I did this.

Watcher.java

@Stateless
@Clustered
public class Watcher
implements WatcherIntLocal, WatcherIntRemote
{

@Resource
private SessionContext context;
@PersistenceContext (unitName="WatcherDB")
private EntityManager em;


public void checkForNewFiles() throws WatcherException
{
try
{
List validFiles = findValidFiles();
addToQueue(validFiles);

}
catch (Throwable e)
{
e.printStackTrace();
throw new WatcherException(e);
}
}

public List findValidFiles() throws WatcherException
{
//iterate thru a list of files and search for certain extensions
//if the file name matches those extensions, call insert
}

public void insert(File file)
{
//// THIS DOES NOT WORK. get a namenotfoundexception
//InitialContext ctx = new InitialContext();
//ConversionFileDAORemote dao = (ConversionFileDAORemote) ctx.lookup("ConversionFileDAO/remote");
//dao.insert(file);

em.persist(file);

//FLUSH DOES NOT WORK. the file is persisted to the db, but only after the watcher is done. this causes the fetcher to get an exception b/c sometimes it can't find the entry in the db
em.flush();
}

public void addToQueue(List validFiles) throws WatcherException
{
// iterate thru files
//create a TextMessage using the file name
//send the message
}
}


==================================
Fetcher.java

public class Fetcher
implements MessageListener
{

@Resource
private MessageDrivenContext context;

@PersistenceContext (unitName="WatcherDB")
private EntityManager em;

public void onMessage(Message arg0) {

String fileName = ((TextMessage)arg0).getText();
File remoteFile = (File)em.createQuery("from File where fileName=:filename").setParameter("filename",fileName).getSingleResult();

transfer(remotefile,localfile);

remoteFile.setStatus("COMPLETE");
em.merge(remoteFile);
em.flush();


}

public void transfer(File remoteFile, File localFile)
{

//// THIS DOES NOT WORK. get a namenotfoundexception
//InitialContext ctx = new InitialContext();
//ConversionFileDAORemote dao = (ConversionFileDAORemote) ctx.lookup("ConversionFileDAO/remote");
//dao.update(file);

remoteFile.setStatus("RUNNING");

em.merge(remoteFile);
//THIS DOES NOT WORK - status of running does not get updated to the db
em.flush();
}

}

=============================
public class ConversionFileDAO implements ConversionFileDAORemote
{

@PersistenceContext (unitName="WatcherDB")
private EntityManager em;

public insert(ConversionFile file)
{
em.persist(file);
em.flush();
}

public update(ConversionFile file)
{
em.merge(file);
em.flush();
}

public getConversionFile(String fileName)
{
ConversionFile currFile = null;

try {
currFile = (ConversionFile)em.createQuery("from ConversionFile where fileName=:filename").setParameter("filename", fileName).getSingleResult();
}
catch (NoResultException e1)
{

}

return file;
}
}