Continuous page reload while debugging using hotswap

Flow
1

Hi,

When I’m using hotswap on my project I get continuous page reloads and I don’t understand why. The moment I log in it starts.

You can see how my network console looks like while not doing anything on a page with just a grid and a couple of rows.

When I set a breakpoint in an onAttach method for example, I see that it continuously arrives there.

I’m using 21.0.5 jbr (installed by sdkman) and Vaadin 24.5.2. I followed the instructions on the vaadin documentation to enable live reload in Intellij. The JBR already has the hotswap-agent shipped with it, and I’ve set the additional flags en enable it in the Run configuration.

The page reloading doesn’t happen when I do a regular debug without Hotswap

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Any ideas what could be happening here?

Kind regards!
Kristof

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2

Which version of Hotswap agent is shipped with the JDK?
The problem may relate to this agent issue that has been fixed in 2.0.1

3

Hmmm,

The logs state that that is the version it’s using

HOTSWAP AGENT: 23:48:23.625 INFO (org.hotswap.agent.HotswapAgent) - Loading Hotswap agent {2.0.1} - unlimited runtime class redefinition.
4

You can try to set logs at debug level for both Flow Hotswapper ( category com.vaadin.flow.hotswap) and the Hotswap agent Vaadin plugin ( LOGGER.org.hotswap.agent.plugin.vaadin=DEBUG in hotswap-agent.properties) to see what is causing the reload.
Another option is to put a breakpoint in com.vaadin.flow.hotswap.Hotswapper.onHotswapInternal() where triggerClientUpdate is called and check what’s in the classes HashSet.

5

Thank you Marco,

I get two breakpoint hits:

  • class com.oriumfit.web.ui.manager.UserOverview$SpringCGLIB$633
  • class com.oriumfit.web.ui.ManagerPage$SpringCGLIB$637

I see the same in the logs

HOTSWAP AGENT: 09:46:29.364 DEBUG (org.hotswap.agent.plugin.vaadin.VaadinPlugin) - Reloading class com.oriumfit.web.ui.ManagerPage$$SpringCGLIB$$305 because of DEFINE
HOTSWAP AGENT: 09:46:29.364 DEBUG (org.hotswap.agent.plugin.vaadin.VaadinPlugin) - Reloading class com.oriumfit.web.ui.ManagerPage$$SpringCGLIB$$305 because of DEFINE
HOTSWAP AGENT: 09:46:29.395 DEBUG (org.hotswap.agent.plugin.vaadin.VaadinPlugin) - Reloading class com.oriumfit.web.ui.manager.UserOverview$$SpringCGLIB$$305 because of DEFINE
HOTSWAP AGENT: 09:46:29.396 DEBUG (org.hotswap.agent.plugin.vaadin.VaadinPlugin) - Reloading class com.oriumfit.web.ui.manager.UserOverview$$SpringCGLIB$$305 because of DEFINE
HOTSWAP AGENT: 09:46:29.911 DEBUG (org.hotswap.agent.plugin.vaadin.VaadinPlugin) - Reloading class com.oriumfit.web.ui.ManagerPage$$SpringCGLIB$$306 because of DEFINE
HOTSWAP AGENT: 09:46:29.912 DEBUG (org.hotswap.agent.plugin.vaadin.VaadinPlugin) - Reloading class com.oriumfit.web.ui.ManagerPage$$SpringCGLIB$$306 because of DEFINE

When I click around in the app, this basically changes to whatever page I’m on, and it’s parent.

I don’t see anything that refers to why it’s happening though :/

Kind regards,
Kristof

6

It seems like Spring is constantly creating and loading new proxy classes for those views.
It could be that fix: trigger refresh on hotswap only for redefined classes by mcollovati · Pull Request #20684 · vaadin/flow · GitHub fixes this issues.
Do you mind upgrading to Vaadin 24.5.9?

1 Like
7

That indeed fixed it!

Thank you Marco! :-)

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