For moderately complex Java Desktop app; should JavaDB connection be static?

Question

I am writing a moderately complex Java desktop app, including an embedded database. I do not see any reason why, after the app establishes a connection to the database, why it should close the connection until the app is going to shut down.

Practically everything one does with the database requires a connection; transactions can be started and completed serially in the connection, the app is not doing anything fantastically complicated with the database.

Is there any reason why I should not create the connection and put a reference to it in a static variable in a class known and used by database-specific classes? It would save having the connection have to be passed around among all kinds of methods without ever changing value.

Is there a design-level consideration I'm missing somewhere?

rc

Answer 1

I would suggest using a library such as c3p0 or dbcp which handles connection pooling for you. It gives you the flexibility to scale up your application later if necessary.

Anything static usually makes it harded to write proper test cases, since you never know if the static resource has been altered or not.

Answer 2

Three months down the road, you're going to want to be able to connect to two databases at the same time - maybe you're doing some import / export work, or an upgrade job, or merging two customers together. And then you're going to want two of them. And now suddenly that static field everyone uses is a nightmare.

You could look into an IoC container like Guice or Spring to ensure that you can keep track of "singleton" objects without abusing static fields to enforce their "Singleton"ness.

Answer 3

Avoid statics. Think on concurrency and multithread issues with this kind of variables. A good point is handle your connections with a database pool. Spring is your friend to reach a simple and nice configuration

Answer 4

I do not see any reason why, after the app establishes a connection to the database, why it should close the connection until the app is going to shut down.

That seems completely fine to me. It's an embedded database; it is at the service of your application. Create the connection when you start, use it as long as you need, shut it down when your application closes down.