Introduction
As of IBM® App Connect Operator v12.16.0, operand version 13.0.5.0-r1, you can now configure the Java version used by the App Connect Enterprise runtime via the IntegrationRuntime custom resource (CR). This enhancement introduces a new "java" field in the IntegrationRuntime CR, which includes a "version" subfield. By setting "version" to either "8" or "17", you can control which Java version the runtime uses.
This blog provides step-by-step instructions for setting and modifying the Java version when creating or updating an IntegrationRuntime instance using both the OpenShift and Dashboard user interfaces.
Note: Only Java versions 8 and 17 are supported. Leaving the version undefined or empty will default to the runtime's built-in Java version. Any unsupported value will result in an error.
OpenShift user interface
Creating IntegrationRuntime using form view
Expand the 'advanced configuration' section at the bottom of the page and then expand the revealed Java section.

Enter a supported Java version (8 or 17) in the "Java version" field and click "Create".
An unsupported value will result in an error.

Creating IntegrationRuntime using YAML view

Add 'java.version' into the outer 'spec' section (not inside 'template').
Set 'version' to '8' or '17' in single quotes, and click "Create".
An unsupported value will result in an error.

Modifying IntegrationRuntime using YAML view
Note: The OpenShift user interface only allows you to edit in the YAML view.

Edit the YAML view to change "spec.java.version" to '8' or '17'.
Click "Save" to apply the change.
An unsupported value will result in an error.

Dashboard user interface
Creating IntegrationRuntime using common settings tab
Enable the "Advanced settings" switch to reveal the Java section.

Click 'Java - Advanced' in the left menu or scroll to the bottom.

Enter a supported Java version and click "Create".
An unsupported value will result in an error.

Creating IntegrationRuntime using YAML editor tab

Add 'java.version' into the outer 'spec' section (not inside 'template').
Set "version" to '8' or '17' in single quotes and click "Create".
An unsupported value will result in an error.

Modifying IntegrationRuntime using common settings tab
Enable the "Advanced settings" switch to reveal the Java section.

Click 'Java - Advanced' or scroll to the bottom.

Enter a supported Java version and click "Create".
An unsupported value will result in an error.

Modifying IntegrationRuntime using YAML editor tab

Edit 'spec.java.version to '8' or '17' in sigle quotes.
Click "Update" to apply the change.
An unsupported value will result in an error.

Troubleshooting Tips
If your application fails to start, check the Java version compatibility.
Ensure 'java.version' is placed correctly in the YAML under rge outer 'spec' section. Indentation matters.
Use single quotes around the version numbers (e.g. '8' or '17').