You could set a five minutes timer to retrieve the data, but BlazeDS is a good choiche it'll give you greater flexibility and as you're confortable with Jave that'll be the way to go.
Thanks for your reply. Could you please pass me any working sample code that I can refer to?
For a Flex/Java/BlazeDS you can go to this blog http://coenraets.org/, there's a sample app named SalesBuilder that'll be very helpful for you I think. If you're looking for an example about the timer look at the docs what you need to do basically is add a timer setting the interval, add event listener when the timer gets the determined time and then call your services and so, then restart the timer.
I understand that Flex uses XML Files as data input for generating charts. How do I query MySQL Database and get the results in XML Files using JAVA and input them to Flex Charts?
Well Flex works pretty well with XML, but it's not the only way. that's a
pretty long question to answer, I recommend you to visit the Flex 3 Getting
Started to see a pretty simple example to create a Flex app with a JAVA
backend. That way will help you better understand how Flex integrates with
backend servers. I assume you know JAVA and how it interacts with MySQL so
that won't be that difficult for you.