Howdy,
>How to implement notifying all online user when the record in database
has
>been changed? I am using Servlet and JSP to build a small Supply-Chain
>system running on Tomcat with MySQL.
Cool design question ;) You probably can't do it immediately on change,
but on the next page the user loads after the change. Here's an
approach:
- Have a Filter mapped to all requests (url-pattern /*) that polls the
DB or listens for the DB change event from another source.
- Have a servlet that displays the contents of this change, let's call
it ServletA
- When the DB changes, the filter is notified and does the following:
- Puts a "notified" attribute with value "false" in every
incoming request
- Gets a RequestDispatcher for ServletA and includes its
contents in the response
- Sets the "notified" attribute to value "true" after
chain.doFilter, i.e. on the response's way back to the browser
It's just an idea, doubtless others will have a different take ;
Yoav Shapira
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