What's interval to validate the idle object in Apache Commons Pool 2

I am using Apache Commons Pool 2, I have set the configuration testWhileIdle to true, which means that the Pool framework will check whether the idle objects they are valid.

I would ask whether this check occurs periodically, if so, what's the default interval, and how i can change it.

I ask so because the objects in the pool should periodically connect to the server to keep alive, and I think pool's validateObject method is a good place to fulfill this.

Per @user7294900's comments,there are two configuration parameters:

1. timeBetweenEvictionRunsMillis, default value is -1
2. minEvictableIdleTimeMillis, default value is 1800*60*30

I have following two question:

1. What's the difference between these two parameters?
2. I set both of them to 5000, and I have 8 objects in the pool, I print the object's hashcode in my PooledObjectFactory's validateObject method, I found that only 3 objects'hash code has been printed out, then there is no more messages printed again, looks the validateObject 's is not called every 5 seconds or the call to validateObject is stuck?

I figured out the problem, please see the comments

You can use\update timeBetweenEvictionRunsMillis for changing time of idle validation, see Tomcat JDBC Connection Pool.

timeBetweenEvictionRunsMillis (int) The number of milliseconds to sleep between runs of the idle connection validation/cleaner thread. This value should not be set under 1 second. It dictates how often we check for idle, abandoned connections, and how often we validate idle connections. The default value is 5000 (5 seconds).