this is a heads-up that minimum required Tomcat version will be 8.5.50 for DHIS version 2.34.
The main reason for this change is Tomcat 7.0 and 8.0 having several issues with certain application development frameworks (most importantly Jackson, used for JSON and XML serialization) used internally by DHIS 2. As part of our effort to keep DHIS 2 secure, we continuously upgrade such frameworks to receive security fixes and this lead to an incompatibility with older Tomcat versions.
All supported DHIS 2 versions are well-tested with Tomcat 8.5 and so we recommend implementors to upgrade their Tomcat version at their earliest convenience.
DHIS 2 dev team