Eric P wrote:
Hi all,
In my Tomcat app I'm looking for a good (or commonly used) method for
firing off an asynchronous task. For example, a user registers for an
account, and an a task to send a verification email to the user is
triggered w/o delaying the response to the user (i.e., task happens in
the background).
I'm somewhat aware that JMS could be used for this and is part of most
J2E environments, but I'd like to see if there's some way to pull this
off w/vanilla Tomcat.
I had a couple ideas that would probably work, but I'd like to see how
others have solved this problem.
One idea would be to insert a record into a database table that
signifies an email should be sent to the user. This table could be
regularly checked by a scheduled job (e.g., a TimerTask) that runs every
minute in the background.
Another (maybe not so good) idea would be to leverage perhaps a session
or request attribute listener that would check for a certain attribute
being added to a session or requests. Then if a 'send email' attribute
comes through, the listener could process an email. This seems like a
bad idea though as I believe the listener event class would be triggered
incessantly any time attributes are added/removed when in fact I'm only
actually interested in the 'send email' attribute.
My grain of salt :
It basically depends on how often you expect this to happen (e.g. a new user registering),
and the acceptable delay before the email is sent.
I like very much the first idea (the database record and separate job), for its simplicity
and robustness. It does not depend on any particular feature or library present in the
servlet engine or the Java version, it does not even depend on the programming language
used to write the email-sending job or the scheduling facilities available on the platform
(think Windows vs Unix/Linux), it makes it easy in the future to change the email to
something else, or add to it, or whatever. It makes it easy to split these tasks onto
separate servers if the need arises (think that host/user-id which runs Tomcat may not be
allowed to send emails; in most corporate environments, you need a "domain user" for that).
It also makes it possible for the emailing job to collect in one single loop all
recipients which need to receive an email, send them all at once, and warn the
administrator and the sales people that 15 new customers just signed up.
---------------------------------------------------------------------
To unsubscribe, e-mail: users-unsubscr...@tomcat.apache.org
For additional commands, e-mail: users-h...@tomcat.apache.org
