In my web application, I have a base class called Dao that contains the following:
Then I have subclasses that extend Dao and inherit the Connection, PreparedStatement, and ResultSet. Here is an example of how they are used:
The reason for doing this is simply that the subclasses always need those variables to do their work, so it seemed sensible to put them in a parent class. Is there any risk or drawback to doing it this way? Is it better to just always declare the Connection, PreparedStatement, and ResultSet as local variables? Thanks for your help.
Thanks for your reply. Can you explain the reason why they should be local variables? What is the danger of putting them in the base class?
I assume you're using a connection pool. In this case, you need to open and close all your database resources as part of servicing every request. This is somewhat obvious for connections, as you want the connection returned to the pool after servicing one request to be available when servicing another request. The other resources have to be closed simply because they are tied to the connection they came from. To reduce the overhead, some connection pools cache these objects (such as PreparedStatements) transparently.
Edit: therefore, you cannot keep these resources open outside of servicing a request, which means they do not belong to the class, but should be declared locally.
Joined: May 15, 2009
OK, sounds like using local variables is the standard way to do it, so I'll go that route. Thanks for your help.
subject: Is it OK to put Statement and ResultSet in DAO base class?