JDBC Event

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Rob McDonald - 28 Jun 2004 19:50 GMT

I'm using Java & JDBC to work with a mySQL database.

I'd like my application to be set off on a course of action when something
in the database is changed. i.e. I'd like the Java app to be an event
listener that listens to the mySQL database for an entry to be updated or
added.

What is the best way to make this happen?

Thanks,

Rob

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Roedy Green - 28 Jun 2004 20:08 GMT

>I'd like my application to be set off on a course of action when something
>in the database is changed. i.e. I'd like the Java app to be an event
>listener that listens to the mySQL database for an entry to be updated or
>added.
>
>What is the best way to make this happen?

You need a database that has triggers -- application code that runs
when various things happen. You need a more advanced SQL engine for
that. I don't know if any of the free ones support them.

For a list of possibilities see http://mindprod.com/jgloss/sql.html

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Canadian Mind Products, Roedy Green.
Coaching, problem solving, economical contract programming.
See http://mindprod.com/jgloss/jgloss.html for The Java Glossary.

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Robert Klemme - 29 Jun 2004 09:27 GMT

> >I'd like my application to be set off on a course of action when something
> >in the database is changed. i.e. I'd like the Java app to be an event
[quoted text clipped - 8 lines]
>
> For a list of possibilities see http://mindprod.com/jgloss/sql.html

Even then the question is whether you could make the trigger call back
into you Java application. I doubt that. I could imagine that this is
somehow possible with Oracle's server side Java support.

Alternatively if your application is the only client of the database you
could put some code in the persistence layer or write a JDBC wrapper that
does the triggering.

Regards

robert

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Tod Landis - 29 Jun 2004 15:05 GMT

Check out:
http://dev.mysql.com/doc/mysql/en/ANSI_diff_Triggers.html

- Tod

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Roedy Green - 29 Jun 2004 16:50 GMT

>Even then the question is whether you could make the trigger call back
>into you Java application. I doubt that.

If your DB Trigger language is Java, you are likely running in a
different JVM than the method you want to talk to, but that does not
mean communication is impossible. You still have sockets, pollable
records, RMI etc. as possible routes of communication.

see http://mindprod.com/jgloss/remotefileio.html

Signature

Canadian Mind Products, Roedy Green.
Coaching, problem solving, economical contract programming.
See http://mindprod.com/jgloss/jgloss.html for The Java Glossary.

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Robert Klemme - 29 Jun 2004 17:23 GMT

> >Even then the question is whether you could make the trigger call back
> >into you Java application. I doubt that.
[quoted text clipped - 3 lines]
> mean communication is impossible. You still have sockets, pollable
> records, RMI etc. as possible routes of communication.

Yes, of course. But I chances are you'll have to implement the
communication on your own (using plain sockets, RMI, CORBA or whatever).

If SP language != Java, then it's even more difficult, although I guess
it's possible to implement SP's in C or some other language where you can
do IO and networking.

Regards

robert

> see http://mindprod.com/jgloss/remotefileio.html

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