I was able to successfully migrate Custom Wrapper from Denodo Platform 7.0 to Denodo Platform 8.0 by performing the following steps in the Virtual DataPort Administration Tool of Denodo Platform 7.0:
* In the VQL shell execute the following commands
SET 'com.denodo.exportMigrationCompatibility' = 'true';
SET 'com.denodo.exportOnlyResourcesAndJars' = 'true';
* In the **Server Explorer Tab**, right-click on the desired Virtual Database that has to be exported and select **Export**.
* In the export dialog box, select the option **Include Jars** and select ok after providing the **Output File**.
* Import the same to Denodo Platform 8.0.
You can take a look at the [Upgrading from Denodo 7.0: Export the Settings and Metadata of the Current Installation](https://community.denodo.com/docs/html/browse/8.0/en//platform/upgrade/export_the_metadata_of_the_current_installation) section of the Denodo Platform Upgrade Guide for more information.
Hope this helps!