How to ensure a MySql connection through Tomcat 8?

Question

I have a webapp that is running properly in Tomcat without the database.

If I add the following to tomcat context.xml it seems to kill the whole server, I get a blank page and connection refused for my app and the tomcat manager app:

<Context docBase="${catalina.base}/webapps/ROOT.war">
    <Parameter name="application.properties" value="/home/users/tomcat/application.properties"/>
</Context>

There is an application.properties file in /home/users/tomcat/ which is the same user that runs tomcat. So how come this line is bringing my server down?

MySQL 5.5 is running and the properties file I used is:

spring.datasource.url=jdbc:mysql://localhost:3306/springboot
spring.datasource.username=automation
spring.datasource.password=xxxxxxxxxxxx
spring.datasource.driver-class-name=com.mysql.jdbc.Driver
#comment out below line to create schema on new database
spring.jpa.hibernate.ddl-auto=update

How do I troubleshoot the database connectivity?

I know mysql is configured for port 3306 and it will let me login with the details in that file, if I use SSH.