I think Rewrite will initialize before any ServletContextListeners, so your startup class won’t be ready when Rewrite initializes.
If you really need the startup class for Rewrite configuration, you should find some other way of initialization. If you are using CDI or Spring, there are many better ways to do this compared to a ServletContextListeners. And manually setting up a connection pool is also not very common. This should be done by the container which will take care of preparing it before the application is deployed.
If you show me the code of your startup class, I could try to give some thoughts for improvement.
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