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From "Jess Holle and Wendy Vidlak" <jessho...@mediaone.net>
Subject RE: Xalan2 in server environment (was Xalan2 Stree Module spans sec ondthread to do transform?)
Date Thu, 11 Jan 2001 04:15:23 GMT
Thanks, Scott.

I doubt it does the trick generally for EJB, but it does the trick for our
app server :-)

EJB is unkind to threaded algorithms to the point that I see this as a major
hole in EJB, though I suppose you could hide this in a Connector and
potentially skirt some of the restrictions....

Still, there *are* algorithms which should be threaded and EJB shouldn't
make it a supreme pain to do this!

--
Jess Holle

-----Original Message-----
From: Scott_Boag@lotus.com [mailto:Scott_Boag@lotus.com]
Sent: Tuesday, January 09, 2001 2:51 PM
To: xalan-dev@xml.apache.org
Cc: tomcat-user@jakarta.apache.org
Subject: Re: Xalan2 in server environment (was Xalan2 Stree Module spans
sec ondthread to do transform?)



In response to this I've created the following method in
org.apache.xalan.TransformerImpl:

  /**
   * Create a thread for the transform.  This can be overridden by derived
   * implementations to provide their own thread, for thread pooling and
the
   * like.
   *
   * @return thread suitable to use for the transformation.
   */
  public Thread createTransformThread()
  {
    return new Thread(this);
  }

Someone who is using XalanJ2 in an EJB environment or the like can set the
javax.xml.transform.TransformerFactory system property to provide a
derivation from TransformerImpl, and provide a thread suitable for the
environment.

I don't know if this will do the trick.  Please advise.

-scott





                    "Roytman,
                    Alex"                 To:
"'xalan-dev@xml.apache.org'" <xalan-dev@xml.apache.org>
                    <roytmana@peac        cc:
"'tomcat-user@jakarta.apache.org'"
                    etech.com>            <tomcat-user@jakarta.apache.org>,
(bcc: Scott Boag/CAM/Lotus)
                                          Subject:     Xalan2 in server
environment (was Xalan2 Stree Module spans
                    01/07/2001            sec ond thread to do transform?)
                    12:14 AM
                    Please respond
                    to xalan-dev






Scott,
Thank you very much for your reply.
One part which is sensitive to thread origin in my opinion is Extensions
In extensions people can do all sorts of things. I am not very experienced
with EJB implementation but I can imagine that many things (transactional
context, bean environment, etc.) depend on threads and some static
variables
which helps with setting /switching context for beans being managed by the
server.

Example: in J2EE it is recommended to create JNDI initial context using
default constructor InitialContext(). The result of the instantiation
depends on the context where it was executed and the context is set by the
server for the thread on which your component is running. So if you call
new
InitialContext() in your extension (in sql extension to get JDBC DataSource
for example ) it might fail.

Do extension run on the second (created by Xalan) thread?

I will forward your message to Tomcat news group lets see what Tomcat
developers think.

Alex

-----Original Message-----
From: Scott_Boag@lotus.com [mailto:Scott_Boag@lotus.com]
Sent: Saturday, January 06, 2001 11:39 PM
To: xalan-dev@xml.apache.org
Subject: Re: Xalan2 Stree Module spans second thread to do transform?



> In many
> cases component should not attempt to create its own threads.
> For example thread's ContextClassLoader or ThreadLocal variables might
need
> to be initialized by the server.
> Also it defeats thread pooling done by the server etc.
>
> Could you please comment on this issue

Yeah, I've been a bit worried about this.  However, I've not yet heard of
any problems that have been caused by it, and XalanJ1 has long had a two
threaded system (though not as effective as in XalanJ2).   Ultimately, I
would rather use a pull model for this, and only have one thread, but a)
there is no standard "pull" API for XML parsers, and b) this doesn't work
anyway when SAX events are used, for whatever reason.

I'm open to any input to how Xalan might request the thread from the
servlet environment, though it has to be able to be run outside a servlet
environment too.  Also, it would be good if someone with deep knowledge of
EJB's and the like could comment.  I talked this over in a hallway
conversation with someone who is fairly familiar with EJB's, and he didn't
think there was a problem, though I forget why.  It seems insane/crazy to
me that a component can't use a thread in it's internal modules.

-scott






                    "Roytman,

                    Alex"                 To:
"'xalan-dev@xml.apache.org'" <xalan-dev@xml.apache.org>
                    <roytmana@peac        cc:     (bcc: Scott
Boag/CAM/Lotus)
                    etech.com>            Subject:     Xalan2 Stree Module
spans second thread to do transform?


                    01/06/2001

                    10:48 PM
                    Please respond

                    to xalan-dev









Dear Xalan developers,
I have a question about using upcoming Xalan2 in server env.

In Xalan2 design specs it is said:

"The Stree module implements the default Source Tree for Xalan, that is to
be transformed. It implements read-only DOM2 interfaces, and provides some
information needed for fast transforms, such as document order indexes. It
also attempts to allow a streaming transform by launching the transform on
a
secondary thread as soon as the SAX2 StartDocument event has occurred."

In server environment server usually controls threads creation. In many
cases component should not attempt to create its own threads.
For example thread's ContextClassLoader or ThreadLocal variables might need
to be initialized by the server.
Also it defeats thread pooling done by the server etc.

Could you please comment on this issue

Thank you very much in advance

Alex Roytman








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