Way to know table is modified

There are two different processes developed in Java running independently, If any of the process modifyies the table开发者_StackOverflow社区, can i get any intimation? As the table is modified. My objective is i want a object always in sync with a table in database, if any modification happens on table i want to modify the object. If table is modified can i get any intimation regarding this ? Do Database provide any facility like this?

We use SQL Server and have certain triggers that fire when a table is modified and call an external binary. The binary we call sends a Tib rendezvous message to notify other applications that the table has been updated.

However, I'm not a huge fan of this solution - Much better to control writing to your table through one "custodian" process and have other applications delegate to that. To enforce this you could change permissions on your table so that only your custodian process can write to the database.

The other advantage of this approach is being able to provide a caching layer within your custodian process to cater for common access patterns. Granted that a DBMS performs caching anyway, but by offering it at the application layer you will have more control / visibility over it.

No, database doesn't provide these services. You have to query it periodically to check for modification. Or use some JMS solution to send notifications from one app to another.

• You could add a timestamp column (last_modified) to the tables and check it periodically for updates or sequence numbers (which are incremented on updates similiar in concept to optimistic locking).
• You could use jboss cache which provides update mechanisms.

One way, you can do this is: Just enclose your database statement in a method which should return 'true' when successfully accomplished. Maintain the scope of the flag in your code so that whenever you want to check whether the table has been modified or not. Why not you try like this???

If you're willing to take the hack approach, and your database stores tables as files (eg, mySQL), you could always have something that can check the modification time of the files on disk, and look to see if it's changed.

Of course, databases like Oracle where tables are assigned to tablespaces, and tablespaces are what have storage on disk it won't work.

(yes, I know this is a bad approach, that's why I said it's a hack -- but we don't know all of the requirements, and if he needs something quick, without re-writing the whole application, this would technically work for some databases)