Refuse to install openHAB 5 if no Java 21 (after potential Java install) (#2020)

Author: mstormi

functions/openhab.bash

@@ -31,7 +31,9 @@ openhab_setup() {
   local installVersion
   local repo
   local successText
+  local noJVMText="We were unable to install/upgrade your system to openHAB 5.\\nThis requires Java version 21, and we have been unable to identify and install a suitable Java JVM package for your hardware-OS combo."
   local ohPkgName="openhab"
+  local textsize=9
 
   if [[ $1 == "snapshot" || $1 == "unstable" ]]; then
     introText="Proceed with caution!\\n\\nYou are about to switch over to the latest $ohPkgName unstable snapshot build. The daily snapshot builds contain the latest features and improvements but might also suffer from bugs or incompatibilities. Please be sure to take a full openHAB configuration backup first!\\n\\nBeware that downgrading will not be possible, you can only re-install old software and re-important the config backup you should have made before the upgrade."
@@ -58,7 +60,7 @@ openhab_setup() {
   fi
 
   # date needs to be > Apr 1, 24 for openhab repo signing key to be valid
-  # note RPi have no RTC
+  # note RPis have no real time clock
   if [[ $(date +%y%m%d) -lt 240401 ]]; then
     systemctl stop systemd-timesyncd
     timedatectl set-time "2024-04-09 00:00:00"
@@ -89,6 +91,20 @@ openhab_setup() {
       fi
     fi
 
+    javaVersionNeu="$(java -version |& head -1 | awk -F'"' '{ print $2 }' | cut -d '.' -f1)"
+    if [[ $openhabMajorVersion = 5 ]] && [[ $javaVersionNeu -lt 21 ]] ; then
+      echo "FAILED (could not install required Java 21)"
+      if [[ -n $INTERACTIVE ]]; then
+        unset DEBIAN_FRONTEND
+        if is_arm && [[ "$(getconf LONG_BIT)" == "32" ]]; then
+          noJVMText+="\\n\\nThere is currently no suitable JVM package for ARM processors that works\\nwith a 32 bit OS image."
+	  textsize=12
+        fi
+        whiptail --title "Operation failed!" --msgbox "$noJVMText" ${textsize} 80
+      fi
+      return 1
+    fi
+
     if [[ -n $openhabVersion ]]; then
       installVersion="${ohPkgName}=${openhabVersion} ${ohPkgName}-addons=${openhabVersion}"
     else