Jasper Studio Java version

Hi team

Following the instructions in 

"Authoring Jasper Report Using ReportTemplate"

https://domain/Windchill-HC/en/#page/Windchill_Help_Center%2FWCCG_BusLogicCust_ReportGeneration_JasperCustomization_AuthoringRTemplate.html%23

At step 12 Jasper Studio compiles some Java using class files exported from Windchill 12.0.2 and gives this error:

java.lang.UnsupportedClassVersionError: com/ptc/wbr/datasource/providers/Site_PartReportWNCProvider has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:763)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:467)
at java.net.URLClassLoader.access$100(URLClassLoader.java:73)
at java.net.URLClassLoader$1.run(URLClassLoader.java:368)
at java.net.URLClassLoader$1.run(URLClassLoader.java:362)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:361)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at java.net.FactoryURLClassLoader.loadClass(URLClassLoader.java:814)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at net.sf.jasperreports.eclipse.classpath.JavaProjectClassLoader.findClass(JavaProjectClassLoader.java:335)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at java.lang.ClassLoader.loadClass(ClassLoader.java:411)
at java.lang.ClassLoader.loadClass(ClassLoader.java:411)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:348)
at net.sf.jasperreports.engine.util.JRClassLoader.loadClassForRealName(JRClassLoader.java:190)
at net.sf.jasperreports.data.provider.DataSourceProviderDataAdapterService.getProvider(DataSourceProviderDataAdapterService.java:92)
at com.jaspersoft.studio.data.jrdsprovider.JrdsProviderDataAdapterDescriptor.getFieldProvider(JrdsProviderDataAdapterDescriptor.java:70)
at com.jaspersoft.studio.data.jrdsprovider.JrdsProviderDataAdapterDescriptor.getFields(JrdsProviderDataAdapterDescriptor.java:55)

It looks as if Jasper is compiling using Java8, but the classes exported from Windchill are Java11. I have changed the Jasper project to use Java11 but this error still occurs. 

The PTC documented steps don't seem to cover the steps needed to make the Java versions compatible. What is needed to get this working?

thanks -- Rick