Purpose

The Confluence installer comes with its own JRE hence Confluence won't use the system JRE when it has been installed using the Installer. To configure Confluence to use the system JRE please follow the steps below:

Solution 

1. Shutdown Confluence
2. Edit <Confluence_Installation_Directory>/bin/setjre.bat for Windows or setjre.sh for Linux

3. Find the following lines

   setjre.bat

   SET "JRE_HOME=<Confluence_Installation_Directory>\jre"

   or

   setjre.sh

   JRE_HOME="<Confluence_Installation_Directory>/jre"; export JRE_HOME

4. Change the JRE_HOME value with the absolute path of your system JRE (or comment out if JAVA_HOME is set.)

5. Save
6. Restart Confluence