would be worth checking if the behavior is different on JDK 17 or older NB versions, since Java changed some defaults of the xml APIs in recent releases.

Validated XML against XSD today with a master build from a few week ago. Worked. This need precise steps to reproduce. And I mean starting from a clean user dir, where to download which XSD, demonstration XML. From my POV XML validation works as it should.

would be worth checking if the behavior is different on JDK 17 or older NB versions, since Java changed some defaults of the xml APIs in recent releases.

Tested this, it does not help. I'll attach files

Validated XML against XSD today with a master build from a few week ago. Worked. This need precise steps to reproduce. And I mean starting from a clean user dir, where to download which XSD, demonstration XML. From my POV XML validation works as it should.

The xsd's with catalog:

xsd.zip

The xml that should validate:

E1-BEm.zip

Validation works, saving does not.

0. I downloaded both zip and put contents into the folder /home/matthias/Downloads/test/:

   matthias@enterprise:~/src/netbeans$ ls -lh /home/matthias/Downloads/test/
   insgesamt 1016K
   -rw-rw-r-- 1 matthias matthias 721K Feb  7 09:03 corpora_linguistics.xsd
   -rw-rw-r-- 1 matthias matthias 259K Apr 26 07:59 E1-BEm.xml
   -rw-rw-r-- 1 matthias matthias 1,1K Apr 28 12:38 fa_tei_catalog.xml
   -rw-rw-r-- 1 matthias matthias  22K Feb  7 09:03 t.xsd
   -rw-rw-r-- 1 matthias matthias 2,3K Feb  7 09:03 xml.xsd
   matthias@enterprise:~/src/netbeans$
   

1. Run NetBeans with a clean user + cachedir nbbuild/netbeans/bin/netbeans --userdir xml-userdir --cachedir xml-cachedir
2. In "Tools -> Plugins -> Installed" select "Java SE" and activate the cluster
3. Go to "Tools -> DTDs and XML Schemas"
4. Choose "Add catalog"
5. Choose "OASIS Catalog Resolver" as Type
6. Enter file:/home/matthias/Downloads/test/fa_tei_catalog.xml as Catalog URL
7. Leave "Prefer Public ID" selected and confirm with "OK"
8. Close Dialog "DTDs and XML Schemas"
9. Open E1-BEm.xml
10. Right click into document choose "Validate XML`

I get:

XML validation started.
Checking file:/home/matthias/Downloads/test/E1-BEm.xml...
Referenced entity at "file:/home/matthias/Downloads/test/corpora_linguistics.xsd".
Referenced entity at "file:/home/matthias/Downloads/test/t.xsd".
Referenced entity at "file:/home/matthias/Downloads/test/xml.xsd".
XML validation finished.

12. Stop NetBeans, start again as in step 2
13. Check "Tools -> DTDs and XML Schemas"

=> Catalog is not there anymore

Problem is there since at least NB 9 (I suspect this never worked).

I can confirm that when choosing OASIS catalog resolver, validation works, also when running netbeans with non-empty user and cache dirs. When choosing XML catalog, validation does not work.

@eduarddrenth a fix is available from #8489, which should cover the problems raised here. A dev/nightly build is available from the checks page or directly: https://github.com/apache/netbeans/suites/38113223012/artifacts/3064311337. It would be great if you could test it.

Tested with the dev build. Validation works with oasis catalog (which is now the default when adding a catalog). After closing and reopening netbeans, validation still works.
Thanks!