jython-users

[Jython-users] Trouble with getting to EJB

[Mike H. <th...@bi...>]

Hello,

I'm trying to use Jython to get to some EJB objects via JBoss 2.2 and
having very little luck.  I can get to the database from another
application (that also uses the EJB, but is Java) so I know that it is
being deployed properly.

According to the JBoss startup, my database is being deploy thus:
		  [jdbc/WP30] Starting
		  [jdbc/WP30] XA Connection pool jdbc/WP30 bound to java:/jdbc/WP30
		  [jdbc/WP30] Started

But when I try to get at it via zxODBC, it doesn't work:
		  >>> from com.ziclix.python.sql import zxJDBC
		  >>> jndi = "jdbc/WP30"
		  >>> db = zxJDBC.lookup(jndi)
		  Traceback (innermost last):
			 File "<console>", line 1, in ?
		  DatabaseError: jdbc not bound 

And there is a jndi.properties file in that directory, and Jython is
reading it.  I know this because if I muck with it, it give me an error:
 
original jndi.properties:
		  java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
		  java.naming.provider.url=localhost
		  java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces

messed-up jndi.properties:
		  java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
		  java.naming.provider.url=fred://localhost
		  java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces

Run with bad jndi.properties:
		  >>> from com.ziclix.python.sql import zxJDBC
		  >>> jndi = "jdbc/WP30"
		  >>> db = zxJDBC.lookup(jndi)
		  Traceback (innermost last):
			 File "<console>", line 1, in ?
		  DatabaseError: fred

Now, I am totally lost.  What could the problem be?  Is there any
suggestions?

-- mikeh

-- 

RE: [Jython-users] Trouble with getting to EJB

[brian z. <bz...@zi...>]

Mike,

The behaviour you are seeing from JBoss and zxJDBC is expected and
correct.  I'll try to explain why and hopefully provide a couple
solutions/suggestions to help you out.

First, zxJDBC doesn't really have anything to with EJBs.  While both
EJBs and zxJDBC can access JNDI they have no relation to each other.
zxJDBC understands how to connect to database from a JNDI lookup that
results in a DataSource or other JDBC object
(ConnectionPooledDataSource, Driver, ...) but can't do anything with
EJBs.  It is often the case that JNDI is used without ever deploying an
EJB, such as when using JMS.

The next thing is to look at what is stored in JNDI and who can access
it.  JBoss binds the DataSource in the 'java:' namespace, which as this
thread
(http://www.mail-archive.com/jbo...@li.../msg12942.h
tml) explains, is available only inside the vm.

So the reason your access to 'java:/jdbc/WP30' fails is because you are
running in another VM (I'm making an assumption here given by the
command prompts in your email).  The reason your EJB can access this
JNDI bound object is because it's part of the container and therefore
can see it.  The JBoss JNDI server is simply denying zxJDBC access to
anything bound under java: as this is intended behaviour.

To prove this try the following code snippet:

 import java
 from javax.naming import *

 env = java.util.Hashtable()
 
env.put(Context.INITIAL_CONTEXT_FACTORY,"org.jnp.interfaces.NamingContex
tFactory")
 env.put(Context.PROVIDER_URL, "localhost")
 env.put(Context.URL_PKG_PREFIXES,"org.jboss.naming:org.jnp.interfaces")

 ctx = InitialContext(env)
 enum = ctx.list("/")
 while enum.hasMoreElements():
  print " -- " + enum.nextElement().getName()

When I run this against my JBoss 2.4.4 instance I see:

 -- XAConnectionFactory
 -- jmx:mountain:rmi
 -- TopicConnectionFactory
 -- UserTransactionSessionFactory
 -- RMIXAConnectionFactory
 -- QueueConnectionFactory
 -- topic
 -- queue
 -- ConnectionFactory
 -- RMIConnectionFactory
 -- UserTransaction
 -- jmx
 -- servercollector
 -- UILXAConnectionFactory
 -- UILConnectionFactory

Notice the 'java:' namespace is not visible.  You'll be unable to access
the connection externally even though your EJB (running internally) sees
it just fine.

If you're looking to just store a DataSource in JNDI you could try
something like this (it's how I test zxJDBC and on occasion I run zxJDBC
this way):

 import java, org
 from javax.naming import *
 from com.ziclix.python.sql import zxJDBC as zx

 env = java.util.Hashtable()
 
env.put(Context.INITIAL_CONTEXT_FACTORY,"org.jnp.interfaces.NamingContex
tFactory")
 env.put(Context.PROVIDER_URL, "localhost")
 env.put(Context.URL_PKG_PREFIXES,"org.jboss.naming:org.jnp.interfaces")

 ctx = InitialContext(env)

 ds = org.gjt.mm.mysql.MysqlDataSource()
 ds.setServerName("192.168.1.102")
 ds.setDatabaseName("ziclix")
 ds.setUser("jython")
 ds.setPassword("jython")
 ds.setPort(3306)
 conn = ds.getConnection()
 conn.close()
 print
 print "opened connection from ds: %s" % (str(ds))

 try:
  ctx.bind("mysql", ds)
 except NameAlreadyBoundException:
  pass

 db = zx.lookup("mysql",
  INITIAL_CONTEXT_FACTORY="org.jnp.interfaces.NamingContextFactory",
  PROVIDER_URL="localhost",
  URL_PKG_PREFIXES="org.jboss.naming:org.jnp.interfaces"
 )

 print
 print db

 db.close()

 ctx.unbind("mysql")

 ctx.close()

This script creates a DataSource (could be a ConnectionPooledDataSource
as well (also note that each vendor's DataSource is slightly different
in terms of set/get API)) and binds the instance.  zxJDBC's lookup() is
then able to find the DataSource and create a connection.  If you re-run
the first code snippet without unbinding mysql you should see it in the
list.

Additionally, if you embed Jython in the EJB container and use the
embedded interpreter to accces zxJDBC and JNDI resources your original
attempt should work just fine.  This approach is also possible for using
zxJDBC in conjunction with PyServlet.

I hope this helps.  If you have any more questions please let me know.

thanks,

brian


> -----Original Message-----
> From: jyt...@li... 
> [mailto:jyt...@li...] On Behalf 
> Of Mike Hostetler
> Sent: Thursday, February 28, 2002 9:54 AM
> To: jyt...@li...
> Subject: [Jython-users] Trouble with getting to EJB
> Importance: High
> 
> 
> Hello,
> 
> I'm trying to use Jython to get to some EJB objects via JBoss 
> 2.2 and having very little luck.  I can get to the database 
> from another application (that also uses the EJB, but is 
> Java) so I know that it is being deployed properly.
> 
> According to the JBoss startup, my database is being deploy thus:
> 		  [jdbc/WP30] Starting
> 		  [jdbc/WP30] XA Connection pool jdbc/WP30 
> bound to java:/jdbc/WP30
> 		  [jdbc/WP30] Started
> 
> But when I try to get at it via zxODBC, it doesn't work:
> 		  >>> from com.ziclix.python.sql import zxJDBC
> 		  >>> jndi = "jdbc/WP30"
> 		  >>> db = zxJDBC.lookup(jndi)
> 		  Traceback (innermost last):
> 			 File "<console>", line 1, in ?
> 		  DatabaseError: jdbc not bound 
> 
> And there is a jndi.properties file in that directory, and 
> Jython is reading it.  I know this because if I muck with it, 
> it give me an error:
>  
> original jndi.properties:
> 		  
> java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
> 		  java.naming.provider.url=localhost
> 		  
> java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
> 
> messed-up jndi.properties:
> 		  
> java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory
> 		  java.naming.provider.url=fred://localhost
> 		  
> java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces
> 
> Run with bad jndi.properties:
> 		  >>> from com.ziclix.python.sql import zxJDBC
> 		  >>> jndi = "jdbc/WP30"
> 		  >>> db = zxJDBC.lookup(jndi)
> 		  Traceback (innermost last):
> 			 File "<console>", line 1, in ?
> 		  DatabaseError: fred
> 
> Now, I am totally lost.  What could the problem be?  Is there 
> any suggestions?
> 
> -- mikeh
> 
> -- 
> 
> _______________________________________________
> Jython-users mailing list
> Jyt...@li...
> https://lists.sourceforge.net/lists/listinfo/jython-users
> 

[Jython-users] Threads

[Stephen N. <ste...@co...>]

I'm not sure as to how to go about threading a jython program.  I am
trying to use from java.lang import Thread, extending the Thread class
and overriding thr run method.  However, when I do this in jython, I get
an error telling me the __call__ attribute has not been set.

If anyone can provide a small example of how to create a threaded app in
jython I would be very grateful.

Thanks

Stephen

Re: [Jython-users] Threads

[Kevin B. <kb...@ca...>]

Stephen Naicken wrote:
> 
> I'm not sure as to how to go about threading a jython program.  I am
> trying to use from java.lang import Thread, extending the Thread class
> and overriding thr run method.  However, when I do this in jython, I get
> an error telling me the __call__ attribute has not been set.

As a design principle, it is often better to implement Runnable rather than extending Thread (you have Runnable jobs to do, rather than anything that would change the semantics of a Thread).

> If anyone can provide a small example of how to create a threaded app in
> jython I would be very grateful.

Four small examples (Jython tends to violate Python's "one obvious way to do it" principle), ordered as Python over Java, then preferred over less preferred:

def greet( name ):
    print "greetings", name

count = 0

# newer Python way
import threading
count += 1
t = threading.Thread(
    target=greet,
    name="MyThread %d" % count,
    args=( "threading.Thread", )
    )
t.start()

# older Python way
# has no thread naming feature
import thread
thread.start_new_thread(
    greet,
    ( "thread.start_new_thread", )
    )

# preferred Java way
from java.lang import Thread, Runnable
class GreetJob( Runnable ):
    def __init__( self, name ):
        self.name = name
    def run( self ):
        greet( self.name )
count += 1
t = Thread( GreetJob( "Runnable" ), "MyThread %d" % count )
t.start()

# other Java way
from java.lang import Thread
class GreetThread( Thread ):
    def __init__( self, name, count ):
        Thread.__init__( self, "MyThread %d" % count )
        self._name = name  # Thread has a 'name' attribute
    def run( self ):
        greet( self._name )
count += 1        
t = GreetThread( "Thread subclass", count )
t.start()

*whew*

BTW, the thread naming stuff is good practice but not required.

kb