I want to use HikariCP. I have a bunch of DAOs tha...

# getting-started

[Jasin Colegrove]

I want to use HikariCP. I have a bunch of DAOs that implement an interface for CRUD operations. What is the best way to pass around the DB connection to get the best use out of connection pooling?

[Rob Elliot]

You should construct a single instance of HikariDataSource at application startup:
https://github.com/brettwooldridge/HikariCP#rocket-initialization

Pass that single instance as a constructor parameter (with type javax.sql.DataSource) to the DAOs.

Then just use dataSource.getConnection().use { connection -> TODO("your code using the connection here") } inside the DAO - it will reuse a pooled connection as far as possible.

[Rob Elliot]

(This is a bare metal description - are you not using some higher level abstraction than java.sql.Connection inside your DAOs? And are you wiring up your application by hand?)

[Rob Elliot]

One neat trick - if you build your data source like this:

val dataSource = HikariDataSource(HikariConfig().apply {
        initializationFailTimeout = -1
        connectionTimeout = Duration.ofSeconds(1).toMillis()
    })

then it will not block on startup or blowup if the DB is inaccessible, only when you try to get a connection will you get an exception after 1 second. So your app will be resilient to the DB being there or not. The default connection timeout of 30 seconds is a bit long!

[Jasin Colegrove]

I am using ktorm. So I am constructing the datasource and passing it to ktorm. so should i still be passing in the datasource to my DAO classes or passing in the ktorm connection instance?

[Rob Elliot]

Reading the docs: https://www.ktorm.org/en/connect-to-databases.html#Connect-with-a-Pool

It looks like you want to do this at application startup:
val database = Database.connect(HikariDataSource(HikariConfig())
and then pass in database to your DAO classes.

[Rob Elliot]

Worth reading this on safe cleanup: https://github.com/brettwooldridge/HikariCP/issues/210#issuecomment-64896185

[Jasin Colegrove]

thank you