The javax.activation classes this module needed were removed in Java 11, and unfortunately that is the version of Java that Mendix 8 and above uses.
The iCalendar module will need a rewrite before you can use it on Mendix 8 I’m afraid.
Sorry!
The error message i get is:
Buildfile: C:\Users\Nick\Documents\Mendix\Workspace Reservations App-main\deployment\build_core.xml
compile:
[javac] Compiling 13 source files to C:\Users\Nick\Documents\Mendix\Workspace Reservations App-main\deployment\run\bin
[javac] C:\Users\Nick\Documents\Mendix\Workspace Reservations App-main\javasource\icalendarmodule\actions\Appointment_SendNotification.java:18: error: package javax.activation does not exist
[javac] import javax.activation.CommandMap;
[javac] ^
[javac] C:\Users\Nick\Documents\Mendix\Workspace Reservations App-main\javasource\icalendarmodule\actions\Appointment_SendNotification.java:19: error: package javax.activation does not exist
[javac] import javax.activation.MailcapCommandMap;
[javac] ^
[javac] C:\Users\Nick\Documents\Mendix\Workspace Reservations App-main\javasource\icalendarmodule\actions\Appointment_SendNotification.java:96: error: cannot find symbol
[javac] MailcapCommandMap mc = (MailcapCommandMap) CommandMap.getDefaultCommandMap();
[javac] ^
[javac] symbol: class MailcapCommandMap
[javac] location: class Appointment_SendNotification
[javac] C:\Users\Nick\Documents\Mendix\Workspace Reservations App-main\javasource\icalendarmodule\actions\Appointment_SendNotification.java:96: error: cannot find symbol
[javac] MailcapCommandMap mc = (MailcapCommandMap) CommandMap.getDefaultCommandMap();
[javac] ^
[javac] symbol: class MailcapCommandMap
[javac] location: class Appointment_SendNotification
[javac] C:\Users\Nick\Documents\Mendix\Workspace Reservations App-main\javasource\icalendarmodule\actions\Appointment_SendNotification.java:96: error: cannot find symbol
[javac] MailcapCommandMap mc = (MailcapCommandMap) CommandMap.getDefaultCommandMap();
[javac] ^
[javac] symbol: variable CommandMap
[javac] location: class Appointment_SendNotification
[javac] 5 errors
BUILD FAILED
C:\Users\Nick\Documents\Mendix\Workspace Reservations App-main\deployment\build_core.xml:29: Compile failed; see the compiler error output for details.