"SEVERE: Error filterStart" - Occurs when starting Tomcat
This problem basically occurs when you've different java versions for compiling the source code and for starting the Tomcat server.
Checks you've to do:
1. Java version of your IDE with what you compile the source code
2. Java version used by Tomcat
If the above mismatches, you'll face the error "SEVERE: Error filterStart" during the Tomcat server start and your web application will not be deployed.