Netbeans debugger doesn't support changing parameters in classes

[Eccenux]

Description

I just started testing jRebel and used jRebel's plugin. Everything seems to work fine on jRebel side.

Steps

Step 1. I've setup jRebel in large project (used the Maven plugin method).

Step 2. Deployed project via Netbeans (CTRL+F5).

Step 3. I add a parameter:

E.g. I have this method:

	@RequestMapping(method = RequestMethod.GET)
	@ResponseBody
	public ExtJSResultListGrid getList(
			@RequestParam(value = "query", required = false) String query,
			HttpSession session
	) throws RequestFailedException, IOException {
		final LibrarianContext librarianContext = librarianContextProvider.getLibrarianContext();
		checkContext(librarianContext, session);

		var listDTO = readerService.list(librarianContext, query);
		return new ExtJSResultListGrid(listDTO);
	}

Change it to add test11 param:

	public ExtJSResultListGrid getList(
			@RequestParam(value = "query", required = false) String query,
			@RequestParam(value = "test11", required = false) String test11,
			HttpSession session
	) throws RequestFailedException, IOException {
		LOG.warn("jRebel test11: {}", test11);

Step 4a. I get this in Tomcat log:

2025-09-29 17:22:21 JRebel: Reloading class 'pl.mol.molnet.ext.reader.ReaderController$UpdateManyParams'.
2025-09-29 17:22:21 JRebel: Reloading class 'pl.mol.molnet.ext.reader.ReaderController'.
2025-09-29 17:22:22 JRebel: Reconfiguring reprocessed bean 'readerController' [pl.mol.molnet.ext.reader.ReaderController]

Step 4b. But I also get this in Netbeans Debugger Console:

The debugger does not support Hot Fix action, details: delete method not implemented

Step 5. I refresh view and I get the new log:

2025-09-29 17:22:29.0050 WARN : pl.m.ext.reader.ReaderController jRebel test11: null

Use case/motivation

It seems like hot fix works on the server (Tomcat) but the Netbeans debugger cannot handle it. It seems like something Netbeans can fix, right? Or is the debugger replaceable by plugins (and perhaps there is better debugger already)?

As I understand same steps should work in InteliJ.

Related issues

No response

Are you willing to submit a pull request?

No

[Eccenux]

I think this fixed it (perhaps it should be the default option in NB?):

• Open file: „C:\Program Files\Apache NetBeans\etc\netbeans.conf”.
• Find options: „netbeans_default_options="..."”;
• Append before final quote: „-J--add-opens=jdk.jdi/com.sun.tools.jdi=ALL-UNNAMED”.

Either this or upgrading Tomcat 9, but my guess is it was this JDI option in NB conf.

[matthiasblaesing]

The normal "Apply Code Changes" execution as supported by OpenJDK work ok (tested with a trivial maven project).

This is hard to fix as jrebel can't be used without a payed license. Blindly adding add-opens will not work as this will clutter the codebase without a validation option. So someone with a jrebel license will need to step up to analyse the problem (what is the problem at its core) and what is the minimal required fix. The next question is then whether the fix is sustainable or not.

[mbien]

we are trying to reduce usage of JDK encapsulation breaking flags where possible (e.g one attempt would be #8739).

one of the log lines you posted is actually from NetBeans:

netbeans/java/debugger.jpda.projects/src/org/netbeans/modules/debugger/jpda/projects/Bundle.properties

Line 29 in d621d18

MSG_CanNotFix=The debugger does not support Hot Fix action.

If we could detect the situation in code we could potentially improve the log message and mention the JMS flag, but I would try to avoid adding more flags out of the box for functionality NB doesn't need during regular operation (without JRebel for example).