Recently we migrated an ADF app from 12.1.3 to 12.2.1 and we faced a problem with the log messages in the application server.
Specifically, the deployed application returned zero log messages when navigating to em>application>Logs>view Log messages.
The log configuration and the search results are as you can see in the following screenshots:
After many checks and dummy applications we found out that this was not a migration issue as we first thought, but a 12.2.1 issue. The cause for this is the entry Weblogic-Application-Version in the MANIFEST.MF file that is used for the versioning of the application. If the deployed project does not include a manifest file, or if this specific entry is missing then the log messages in EM are queried correctly.
For some reason it seems that this entry causes a configuration issue on where EM needs to look for the logs.
Silver lining, the logs are not completely gone! If you check the diagnostic log files of the server you will find all the application logs (depending on how you have configured your loggings).
So, if you are using Weblogic-Application-Version in your Manifest file, you will probably need to configure your weblogic and check the logs from the diagnostic files instead of the provided query page for the application.