EntityManager - IllegalStateException: No application context active

[chrisbird]

In the code below:

@Name("startupThread")
@Scope( ScopeType.APPLICATION )
@Startup
public class StartupThread extends Thread
{
        private Thread t;
       
        @In
        EntityManager entityManager;
       
        @Create
        public void init( )
        {
                List<X> xs = entityManager.createQuery( "select x from X x" ).getResultList( );
                t = new StartupThread( );
                t.start( );
        }
       
        public void run( )
        {
                while( true )
                {
(*)                     EntityManager em = (EntityManager)Component.getInstance( "entityManager" );
                        List<X> xs = entityManager.createQuery( "select x from X x" ).getResultList( );
                       
                        try { Thread.sleep( 3000L ); }  catch( Exception ex ) { }
                }
        }
}

there is an exception:
Exception in thread "Thread-20"
java.lang.IllegalStateException: No application context active
     at org.jboss.seam.Component.forName(Component.java:1945)
     at org.jboss.seam.Component.getInstance(Component.java:2005)
     at org.jboss.seam.Component.getInstance(Component.java:1983)
     at org.jboss.seam.Component.getInstance(Component.java:1977)
     at org.jboss.seam.Component.getInstance(Component.java:1972)
     at org.domain.jakis.session.StartupThread.run(StartupThread.java:51)

throwed from the line:
     EntityManager em = (EntityManager)Component.getInstance( "entityManager" );

What is a reason of the exception? I'am a newbe and I need your help.

[kapitanpetko]

Since this spins off a new thread, it has no access to Seam contexts. That's the way Seam works: contexts are bound to the (servlet) thread.
And you shouldn't use threads in an application server anyway. One way to solve it is to have a component with an asynchronous method that does the work and call it from StartupThread (which shouldn't be a Thread, so maybe just Startup is a better name. Read about it: Asynchronicity and messaging

What exactly are you trying to achieve?

[chrisbird]

I need a component that transfer data in background between two tables in time intervals and control this component from another component (accessed from facelet), for example:

@Name( "transferHome" )
public class transferHome extends EntityHome<AnyData>
{
    ...
    @In
    private StartupThread startupThread;
   
    public void x( )
    {
         startupThread.y( );
    }
    ...
}

[kapitanpetko]

So write a component with an asynchronous method and call it from TransferHome (without extending Thread). Something like:

public class Transfer {

 @Ascynchronous
 public void transfer() {
 }
}

[chrisbird]

Thanks for your answer! Asynchronous tasks aren’t covered in 'Seam in Action' which I was read.