Finally, if you decide to use the extra rule to control the value generation of JSP attributes, you need also register the rule into UNICOM® Digital Transformation Toolkit (UDTT™) tooling extension to indicate the path of the configuration file which contains the mapping rules. For that, you could define an extension for the extension point 'com.ibm.btt.tools.xui.editor2.generator'. Then like the picture below, add a child option of type 'rule'.
Like the picture shown below, the required attributes 'name' and 'class' should be configured. Especially for the attribute 'class', you need to indicate the full path to a class which implements the interface 'com.ibm.btt.tools.xui.editor2.generator.IRule'. During the JSP generation, the class would be instantiated and executed for the configured mapping rules.
So, what you need to do is to add your codes for the attribute value conversion like the snippet above.