Creating a "context" for an application...or something like that

Question

hey all. I've got a console program that runs all the time, on a TimerTask. What I would like to do is create objects in the main class and have those objects available to other classes and threads generated by the stuff the TimerTask's thread creates, but without passing objects around. Sort of like one would do with servlet/jsp programming with contexts and the request scope and such.
I come from a web background, and so I think about this very much like a "scope" thing, where objects can be created and put in the request scope, and then other objects can avail themselves of stuff in the request scope.
What i'm really trying to do is create a DB Connection pool in the main class and have threads and such use the connections, but i don't want to pass the pool object around to all the different objects within the TimerTask's thread. But this is more a question of scoping or availability of objects than it is about DBCP, per se.
I feel like I should have learned this stuff in java 101 way back when, but I didn't, or I forgot, and now i need to gitterdone.
Any tips? Thanks os much.

Answer 1

hey all. I've got a console program that runs all
the time, on a TimerTask. What I would like to do is
create objects in the main class and have those
objects available to other classes and threads
generated by the stuff the TimerTask's thread
creates, but without passing objects around. Sort of
like one would do with servlet/jsp programming with
contexts and the request scope and such.In fact, with servlets and JSPs, the objects are passed around via a ServletConfig object (the servlet's public void init(ServletConfig config) method) for the application (ServletContext) scope. The request scope of course is passed along to the service methods in the ServletRequest object, as is the HttpSession scope. The PageContext is generated in a JSP at the beginning of the _jspService method...
But anyway, that is not what you need to do... If you want one context that the whole application can use, you can create a Singleton class, and use a static method from the class (of a Factory Object) to generate the Context/pass around the already generated Context. Take a www.google.com search for Singleton and you should see what I mean. But, since you will be working with multiple threads, make sure you sinchronise your methods...
I come from a web background, and so I think about
this very much like a "scope" thing, where objects
can be created and put in the request scope, and then
other objects can avail themselves of stuff in the
request scope.If you want more than one Context, then that is a bit more difficult. What I would do is have some sort of TaskFactory that generates your classes (Tasks) that run in the Timer. Follow the Servlet example of having a TaskConfig object that will hold a reference to the single ApplicationContext that all tasks share, then generates a new TaskContext that will serve individual threads. Pass this TaskConfig object into each of your class's init(...) methods. (Maybe have an AbstractTask that has an init(TaskConfig ) method that stores it in a protected class variable so each individual Task doesn't have to worry about it - like the GenericServlet does...)
What i'm really trying to do is create a DB
Connection pool in the main class and have threads
and such use the connections, but i don't want to
pass the pool object around to all the different
objects within the TimerTask's thread. I think this is usually done with a Singlton, I could be wrong though... I beleive a search through the forums for Connection Pooling may provide some examples...
But this is
more a question of scoping or availability of objects
than it is about DBCP, per se.
I feel like I should have learned this stuff in java
101 way back when, but I didn't, or I forgot, and now
i need to gitterdone.
Any tips? Thanks os much.