Exception in thread "main" java.lang.ClassNotFoundException: com.liferay.portal.tools.DBUpgrader

Issue

While attempting to upgrade to the Liferay Quarterly Release, the following error was encountered, and the upgrade process failed:

Exception in thread "main" java.lang.ClassNotFoundException: com.liferay.portal.tools.DBUpgrader
 at java.base/java.net.URLClassLoader.findClass(URLClassLoader.java:445)
 at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:593)
 at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:526)
 at com.liferay.portal.tools.db.upgrade.client.DBUpgraderLauncher.main(DBUpgraderLauncher.java:33)

Environment

All Quarterly Release

Resolution

To resolve this issue and ensure the upgrade proceeds smoothly, modify the dir property by removing the version of Tomcat in app-server.properties file: (Path: Liferay_Home> tools> portal-tools-db-upgrade-client> app-server.properties)
Incorrect:
- ```
dir=../../tomcat-9.0.xx
```
Correct:
- ```
dir=../../tomcat
```

The full corrected configuration looks like this:

dir=../../tomcat
extra.lib.dirs=/bin
global.lib.dir=/lib
portal.dir=/webapps/ROOT
server.detector.server.id=tomcat

After making this change, the upgrade completes successfully without throwing any errors.

Additional Information

Database Upgrade Tool Reference