In Windows, Confluence can't start manually after an upgrade

Summary

In Windows, if Confluence is upgraded to 7.x, a subsequent attempt to start Confluence manually will not work.

Steps to reproduce

1. Install Confluence 7.0.x using the Windows installer.
   • The setjre.bat file should include the line: SET "JRE_HOME=C:
     Program Files\Atlassian\Confluence\jre
2. Verify basic functionality.
3. Download the Confluence 7.5.2 Windows installer.
4. Upgrade Confluence 7.0.x to 7.5.2
5. If the installer fails to shut down the 7.0.x instance, shut down the Windows service for 7.0.x.
6. Continue with upgrade installer.
7. If an error displays "...while attempting to remove the previous installation directory. Some files may be in use...", click Ignore.
8. Installer prompts to Start Confluence and then to launch the browser.
9. Confluence is accessible.
10. If you stop and start the Windows service that the installer built, Confluence should still start up ok.
11. However, if you stop Confluence via the service and then try starting it via the manual start-confluence.bat, the following error is displayed:

    C:\Program Files\Atlassian\Confluence\bin>start-confluence.bat
    
    To run Confluence in the foreground, start the server with start-confluence.bat /fg
    2020.06.25_12.40.32
    2020.06.25_12.40.32
    Neither the JAVA_HOME nor the JRE_HOME environment variable is defined
    At least one of these environment variable is needed to run this program
    Neither the JAVA_HOME nor the JRE_HOME environment variable is defined
    At least one of these environment variable is needed to run this program
    

Environment

Windows operating system
Upgrading from 7.0.x to 7.5.x

Expected result

Confluence can start manually.

Actual result

After executing <confluence-install>/bin/start-confluence.bat, an error is displayed in the command prompt and Confluence doesn't start.

Workaround

1. To get Confluence to start, ensure that the Confluence is not running.
2. Next update the <confluence-install>/bin/setenv.bat file so that the JAVA_HOME environment variable is set to either the packaged JRE location or a separate Java instance on the server within. Here's an example showing a set of JAVA_HOME to packaged JRE location and where to insert this line:

   SET "JAVA_HOME=C:\Program Files\Atlassian\Confluence\jre"
   
   rem IMPORTANT NOTE: Only set JAVA_HOME or JRE_HOME above this line
   

3. Execute <confluence-install>/bin/start-confluence.bat. You may still see the messaging, but Confluence will start.