I need to know why we need a connection pool for a standalone application. According to my knowledge, a standalone application needs only one database connection instance. That's why we use the singleton pattern while creating the connection object using JDBC. So what's the use of having a connection pool for a standalone application? If I am using a connection pool, do I need to specify the max size as 1? Here I am trying to use the CP30 connection pool with native Hibernate.
3 Answers
A major reason for using a connection pool is that it makes it easier for your application to recover in case the connection goes bad. The only time I would not use a connection pool was if it was acceptable for the program to fail if the connection stopped working. An example could be a very simple batch job that executed one transaction and the job framework running it would retry it if it failed.
I agree you have a stand-alone application, but that does not mean, you always need to use a Singleton design pattern. How about a single application spinning up multiple threads and each thread connecting to the database. In that case, Singleton won't be of any help, and you should implement connection pool, you are gracefully handling the db operations.
Connection pool and applications (stand-alone or distributed), are related to some extent, but it majorly depends on the use case. Suppose you are working on a stand-alone desktop based application, which is a simple CRUD one, in that case, I agree you need not implement connection pool, but in case we are talking about multiple user, and that too parallel, I think we should always leverage connection pool.
Not sure what your use-case talks about, but generalizing the statement, "Stand-alone application, does not need connection pooling", does not stand true always.
The cost of using a connection pool is usually insignificant.
Your data access layer does not need to know whether it's being called from a standalone application or, say, a multithreaded web application. So there's a good case for always using connection pooling, which doesn't hurt in the first case and is probably necessary in the second.
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