My application is stucked when DB is down

My application is stucked when DB is down

I'm using Hibernate and Tomcat JDBC connection pool to use my MySQL DB.
When, from any reason, the DB is down, my application got stuck.
For example, I have REST resources (with Jersey), they are not getting any
requests.
I also using quartz for schedule tasks, they aren't running as well.
When I start my DB again, everything goes back to normal.
I don't even know where to start looking, anyone has an idea?
Thanks