Java: Sharing a connection pool accross other J2SE Apps...?

Question

So I have a connection pool setup. Which is great and all since I have an application that really needs it. However what I would like to know is if it is possible to share this connection pool with other J2SE apps? Would this even be worth it, as opposed to creating a connection pool based on each apps needs? If it would be prudent, how can I accomplish this?

Answer 1

It is not hard having connection pools in a single JVM doing multiple things - that is what applications servers do everyday (using JNDI to throw objects across classloaders)

The interesting part is when you have the connection pool in a separate JVM from the client code needing it, as this does not immediately allow simply asking for and getting a connection from the pool and returning it afterwards.

Basically you have two options:

1. Doing remote requests for all your JDBC commands over the network. This will most likely mean that the data will travel over the network twice, from the database to the connection pool, and then from the connection pool to your application. If the database connections are very expensive objects then this might be a viable solution.

2. Use RMI to get the connection object from the connection pool JVM to your own machine. This is a very expensive operation, but can as far as I know include the actual driver classes, allowing your connection pool to provide connections to databases not known to your application JVM. To me this would only make sense if the database connections were ridiculoulusly expensive or it was a requirement to be able to support additional databases after deployment without changing the original deployments.

Note that the primary reason for having connection pools at all is because connections are expensive to create, use shortly and then discard. Some databases more than others, e.g. MySQl is (or was when I tried) very cheap so it might be the simplest just to do that.

So. First of all: Measure what your connection pool buys you in time, and then consider if it is worth your while to centralize this further.