Purpose

Jira 8.0/8.1 supports Oracle JDK 8 however it also contains the majority of changes required for the OpenJDK 11 support. It means you can already run Jira 8.0/8.1 on OpenJDK 11 however Java 11 features are not supported in the source code. The official support will be announced in one of the upcoming Jira 8.x versions.

To run Jira 8.0/8.1 on Java 11, you need to manually update the JDBC driver so that it's compatible with OpenJDK 11. This means replacing the bundled SQL Server driver with the one compliant with either both Java 8 and Java 11 or only Java 11. 

If the driver is not replaced, you will not be able to use SQL Server with Jira 8.0/8.1 running on OpenJDK 11.

Versions

This knowledge base article applies only to Jira 8.0 and 8.1. Jira 8.2 is bundled with the correction version of the JDBC driver, 7.2.1.

Solution

1. Shut down your Jira or, if you're upgrading Jira at the same time, upgrade the driver, before you re-apply modifications. See: Upgrading Jira.
2. Download Java 11 compatible JDBC driver for SQL Server from the Microsoft site. See Microsoft JDBC Driver for SQL Server.
3. Extract the driver jar files.
4. Go to the <Jira-install>/lib  folder.
5. Replace the current mssql-jdbc-6.2.1.jre8.jar driver with the downloaded jar driver. You can use mssql-jdbc-7.x.x.jre8.jar if you need it to be compatible with both Java 8 and Java 11 or mssql-jdbc-7.x.x.jre11.jar if you need Java 11 compatibility only.
6. Go to <installation-directory>/bin, and run start-Jira.bat or start-jira.sh to start Jira. 
7. Open Jira in your browser.