Thomas,
There are two parts - the polling part and the JDBC part. For the polling part - what kind of application is it? If JEE, you can use the timer service. Otherwise, you can start a thread.
Examples of what? You haven't said which approach you are looking at.
Also, what about transaction management? Polling is a read only activity. The other processes that are writing to the database would protect the data's ACID properties.