@melany If you're still using GGTS probably not with the version of Grails you are using. You would have to upgrade to Grails 4, which has Groovy 2.5, which has support for Java 11, although there are still warning: https://dev.to/erichelgeson/removing-illegal-reflective-access-warnings-in-grails-4-393o Since you're still using GGTS I'm guessing you're probably using a Grails 2 version? Upgrading from Grails 2 to 3 can be difficult, the level of difficulty is a function of

how big your codebase is * how many bad practices you follow + converting from gant to gradle

. Upgrading from Grails 3 to 4 is a lot easier, however upgrading from Grails 2 to 4, would incur all that code debt. https://www.google.com/search?sxsrf=ALeKk01KEwQahJXmudygSX9E0PpKpVeeaQ%3A1587298127894&ei=Tz-cXriYNqivytMPvrea6Ac&q=upgrading+grails+2+to+3&oq=upgrading+grails+2+to+3&gs_lcp=CgZwc3ktYWIQAzIECAAQRzIECAAQRzIECAAQRzIECAAQRzIECAAQRzIECAAQRzIECAAQRzIECAAQR1AAWABgnKwCaABwAngAgAEAiAEAkgEAmAEAqgEHZ3dzLXdpeg&sclient=psy-ab&ved=0ahUKEwj4-8KouvToAhWol3IEHb6bBn0Q4dUDCAw&uact=5 https://docs.grails.org/3.0.0/guide/upgrading.html https://docs.grails.org/3.3.0/guide/upgrading.html https://www.google.com/search?sxsrf=ALeKk02r5MJbneTvdfl9xzoU69nnOiuQSw%3A1587298167074&ei=dz-cXoSPBLKHytMPg5qF0A8&q=upgrade+to+grails+4&oq=upgrading+grails+2+to+3&gs_lcp=CgZwc3ktYWIQAxgBMgQIABBHMgQIABBHMgQIABBHMgQIABBHMgQIABBHMgQIABBHMgQIABBHMgQIABBHUABYAGCXnwJoAHACeACAAQCIAQCSAQCYAQCqAQdnd3Mtd2l6&sclient=psy-ab https://docs.grails.org/snapshot/guide/upgrading.html https://dev.to/erichelgeson/grails-4-upgrade-notes-3cja I've upgraded two apps from 2.4/2.5 to Grails 3.0.11/3.3.11. Both times it took quite a bit of effort and a lot of QA cycles. Uprading from Grails 3.3.11 to 4 on the other hand was fairly easy, and only slightly complicated by some legacy code. If you are not up to doing the upgrade, you might want to contract OCI to get help. I would also ditch GGTS at this point as it hasn't been supported in years, and Intellij even with its faults is the best IDE for Grails Development.