UnsupportedClassVersionError When connecting drawio to self-hosted GitLab instance

Preflight Checklist

• I agree to follow the Code of Conduct that this project adheres to.
• I have searched the issue tracker for a feature request that matches the one I want to file, without success.

Describe the bug We recently updated our GitLab to version 15.1.0-ee, and drawio to version 20.0.4 (running in a docker container). With these updates, drawio can no longer connect to GitLab. (We were using GitLab 14.8.2-ee and drawio version 14.0.3, and these were working fine.)

I spent lots of time digging, checking other issues (https://github.com/jgraph/drawio/issues/2192 , https://github.com/jgraph/drawio/issues/2474) get to the bottom of this bug and updated several things following what other people have tried to try to get it to work:

• ensured that all our self-signed certificates are both on the gitlab server and in the drawio container
  • these work, I can curl gitlab from drawio and vice versa without any issues.
• ensured that my gitlab application settings are correct
  • callback to https://diagrams.xxxxxxx.local/gitlab (no .html at the end, and using https)
  • application has the correct scopes (api, read_repository, write_repository)
• set all the correct environment variables in my docker container:

DRAWIO_GITLAB_URL=https://gitlab.xxxxxxx.local
DRAWIO_GITLAB_ID=9b0axxxxxxxxxxxxxxxxxxxxxxxxxxda0a4aeb21c518fcad78517b26b
DRAWIO_GITLAB_SECRET=3867f5xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx96fc353da7ebb562696
DRAWIO_BASE_URL=https://diagrams.xxxxxxxx.local

And when I spin up the drawio page and try to connect, it raises an “Unknown error”. If I inspect the page and look at the actual request, I see that drawio tried to access endpoint https://diagrams.xxxxxxx.local/gitlab?getState=1 and returns a 500 error:

Exception

jakarta.servlet.ServletException: Error instantiating servlet class [com.mxgraph.online.GitlabAuthServlet]
	org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542)
	org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
	org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:690)
	org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:356)
	org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:399)
	org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
	org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:867)
	org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1760)
	org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
	org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
	org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
	org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	java.lang.Thread.run(Thread.java:750)
Root Cause

java.lang.UnsupportedClassVersionError: com/mxgraph/online/GitlabAuthServlet has been compiled by a more recent version of the Java Runtime (class file version 55.0), this version of the Java Runtime only recognizes class file versions up to 52.0 (unable to load class [com.mxgraph.online.GitlabAuthServlet])
	org.apache.catalina.loader.WebappClassLoaderBase.findClassInternal(WebappClassLoaderBase.java:2515)
	org.apache.catalina.loader.WebappClassLoaderBase.findClass(WebappClassLoaderBase.java:877)
	org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1413)
	org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1257)
	org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:542)
	org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
	org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:690)
	org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:356)
	org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:399)
	org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
	org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:867)
	org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1760)
	org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
	org.apache.tomcat.util.threads.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1191)
	org.apache.tomcat.util.threads.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:659)
	org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	java.lang.Thread.run(Thread.java:750)

Note: any subsequent attempts to connect raise a 404. I can only get the 500 error on the first connection attempt when I startup the container.

And at this point, I’m very far down the rabbit hole, I don’t know what to do anymore… Any help is greatly appreciated.

To Reproduce Steps to reproduce the behavior:

1. Install GitLab 15.1.0-ee (on an Ubuntu 20.04.4 LTS machine)
2. Create an application for drawio
3. Install drawio 20.0.4 in a docker container
4. add the application credentials in the container’s environment variables when starting it
5. Install self-signed certificates on GitLab server and drawio container
6. Try to connect to gitlab in the drawio page

Expected behavior Successful connection to gitlab to see, edit, and commit diagrams to repository D Screenshots

draw.io version (In the Help->About menu of the draw.io editor):

• draw.io version 20.0.4 (running in docker container)

[davidjgraph]

Oh, that’s not right, we’ll look.

[m-mohamedin]

Will be fixed in the next release. A manual fix is here https://github.com/jgraph/drawio/issues/2932