Originally, MID Servers were bundled with Oracle's Java Runtime Environment (JRE). ServiceNow MID Servers included our own OpenJDK based JRE build from Madrid onward. This JRE has been what all MID Server-related release testing has been done with since. Since London Patch 8 and Kingston Patch 14b Hot Fix1, the same OpenJDK JRE is tested with and included in those older versions, and can also be used with previous London and Kingston MID Servers. From Paris, the bundled Java 8 OpenJDK will be updated to a more recent patch with every major release. 

The bundled JRE does not have to be used. You may have a requirement to use the latest Java 8 patch or Java 11 instead, for security reasons, or because you need to customise the JRE. You may also need an external JRE in order to preserve cacerts or other JRE settings from being overwritten when the bundled JRE is automatically upgraded. As of the Orlando release, MID Server officially documents that it supports all Oracle and OpenJDK JREs of Java 8 (patch 161 and above) and Java 11. If there is a problem running ServiceNow features and code on a MID Server with one of those non-bundled JREs then it will be treated as a product defect and we will try to provide a workaround or fix.

All

If you do need to use your own OpenJDK JRE with the MID Server, then follow these instructions:

1. Using the vendor's own instructions, Install the JRE in the normal way but be sure to install it outside of the MID Server's "agent" install folder. MID Server upgrades can replace anything included within the agent folder, and do regularly delete and replace everything in the bundled JRE's agent/jre/ folder.
2. Edit the agent/conf/wrapper-override.conf file to tell the MID Server to use the newly installed external JRE. (Use Wordpad and not Notepad on windows, as this is a Unix format file)
3. Restart the MID Server service.

################################################################################
# External JRE
################################################################################
# Uncomment and edit if an external JRE is preferred. By default,
# the internal JRE distribution is used.
#
# OPTIONAL: The path (relative to agent dir or absolute) to the java bin
wrapper.java.command=C:\ServiceNow_MID_Servers\OpenJDK\8u251\jre\bin\java

Warnings:

• You are now responsible for keeping the JRE maintained. ServiceNow upgrades will not touch this JRE.
• If you customise the JRE, perhaps by swapping .jar files within the jre for different versions, then this JRE will no longer be supported by servicenow.