I would say you need to configure JDBC connection pool to test availability of connections.
For example in glassfish you can use is-connection-validation-required="true" connection-validation-method="table" validation-table-name="dual". You need to find out how to configure it in Tomcat.
Then when your application acquires new connection from pool, server should test it before giving it to you.
When connection error occurs during some processing, just treat it as error.
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