JRE vs JDK vs 32-bit vs 64-bit

Eric Carbone April 15, 2019

I have JIRA and Confluence running on the same Windows 2016 Server. JIRA must be using JRE because at the time I last updated JIRA, I did not have JDK installed. It also appears to be using the 32 bit version of JRE. (boo)

This weekend I attempted to upgrade Confluence. It has been working fine all this time, but I just wanted to upgrade. I suppose I should have read the release notes because I am thinking at some point Confluence switched from JRE to JDK. It wasn't until after I upgraded Confluence that I started coming across one stumbling block and another. Somewhere along the way I got a message stating that I need to have JDK. Because JIRA (running on this same server) is using 32-bit JRE I thought it would probably be best to install 32-bit JDK. I did that, followed the instructions to set %JAVA_HOME% to the correct path, reinstalled the Confluence service. It would not start. Gave an error and told me to refer to log files.

I uninstalled the Confluence Service, uninstalled 32-bit JDK, installed the 64-bit JDK, reinstalled the Confluence Service, rebooted the server and now Confluence is working.

So now, onto my questions...

I believe both JIRA and Confluence ship with their own version of JRE and/or JDK. Aside from that, I notice that if I run 'where java' in the command prompt it tells me there are 2 paths:   C:\Program Files (x86)\Common Files\Oracle\Java\javapath\java.exe and C:\ProgramData\Oracle\Java\javapath\java.exe.

Where did these versions come from and why are there two?

And now in addition to that, apparently I have the 32-bit version of JRE which I installed, and the 64-bit version of JDK which I installed. Neither of these are located in the paths mentioned above.

The whole setup just seems messy. Is there a way to get JIRA to run on JDK instead of JRE and if so, can it run on the exact same instance of JDK that I installed for Confluence? (Seems logical that if the OS is 64 bit and the applications (JIRA and Confluence) are 64-bit then I should be using one (and only one) 64-bit Java). And since Confluence requires JDK and JDK includes JRE, why not just have one (and only one) instance of JDK installed, and then how can I (should I) get rid of the other lingering instances of Java?

Just trying to wrap my head around what is used and what isn't, and also make sure I am running the correct version of Java for JIRA and Confluence.

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