In a pipeline, how to check if a Jenkins item is a folder?

[ZillaYT]

I have the following function defined in a pipeline.

private boolean isFolder(Item j) {
  return j.getClass().getName() == "com.cloudbees.hudson.plugins.folder.Folder"  
}

When I run it, I get

an exception which occurred: in field com.cloudbees.groovy.cps.impl.BlockScopeEnv.locals in object com.cloudbees.groovy.cps.impl.BlockScopeEnv@ad9ba3c in field com.cloudbees.groovy.cps.impl.CpsClosureDef.capture in object com.cloudbees.groovy.cps.impl.CpsClosureDef@a44ee1a in field com.cloudbees.groovy.cps.impl.CpsClosure.def in object org.jenkinsci.plugins.workflow.cps.CpsClosure2@13b12418 in field org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.closures in object org.jenkinsci.plugins.workflow.cps.CpsThreadGroup@554cc3b1 in object org.jenkinsci.plugins.workflow.cps.CpsThreadGroup@554cc3b1 Caused: java.io.NotSerializableException: com.cloudbees.hudson.plugins.folder.Folder at org.jboss.marshalling.river.RiverMarshaller.doWriteObject(RiverMarshaller.java:926) at org.jboss.marshalling.river.RiverMarshaller.doWriteObject(RiverMarshaller.java:568) at org.jboss.marshalling.river.BlockMarshaller.doWriteObject(BlockMarshaller.java:65) at org.jboss.marshalling.river.BlockMarshaller.writeObject(BlockMarshaller.java:56) at org.jboss.marshalling.MarshallerObjectOutputStream.writeObjectOverride(MarshallerObjectOutputStream.java:50) at org.jboss.marshalling.river.RiverObjectOutputStream.writeObjectOverride(RiverObjectOutputStream.java:179) at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:344) at java.util.HashMap.internalWriteEntries(HashMap.java:1793) at java.util.HashMap.writeObject(HashMap.java:1363) at sun.reflect.GeneratedMethodAccessor65.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.jboss.marshalling.reflect.JDKSpecific$SerMethods.callWriteObject(JDKSpecific.java:156) at org.jboss.marshalling.reflect.SerializableClass.callWriteObject(SerializableClass.java:191) at org.jboss.marshalling.river.RiverMarshaller.doWriteSerializableObject(RiverMarshaller.java:1028) at org.jboss.marshalling.river.RiverMarshaller.doWriteObject(RiverMarshaller.java:920) at org.jboss.marshalling.river.RiverMarshaller.doWriteFields(RiverMarshaller.java:1082) at org.jboss.marshalling.river.RiverMarshaller.doWriteSerializableObject(RiverMarshaller.java:1040) at org.jboss.marshalling.river.RiverMarshaller.doWriteObject(RiverMarshaller.java:920) at org.jboss.marshalling.river.RiverMarshaller.doWriteFields(RiverMarshaller.java:1082) at org.jboss.marshalling.river.RiverMarshaller.doWriteSerializableObject(RiverMarshaller.java:1040) at org.jboss.marshalling.river.RiverMarshaller.doWriteObject(RiverMarshaller.java:920) at org.jboss.marshalling.river.RiverMarshaller.doWriteFields(RiverMarshaller.java:1082) at org.jboss.marshalling.river.RiverMarshaller.doWriteSerializableObject(RiverMarshaller.java:1040) at org.jboss.marshalling.river.RiverMarshaller.doWriteSerializableObject(RiverMarshaller.java:1019) at org.jboss.marshalling.river.RiverMarshaller.doWriteObject(RiverMarshaller.java:920) at org.jboss.marshalling.river.BlockMarshaller.doWriteObject(BlockMarshaller.java:65) at org.jboss.marshalling.river.BlockMarshaller.writeObject(BlockMarshaller.java:56) at org.jboss.marshalling.MarshallerObjectOutputStream.writeObjectOverride(MarshallerObjectOutputStream.java:50) at org.jboss.marshalling.river.RiverObjectOutputStream.writeObjectOverride(RiverObjectOutputStream.java:179) at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:344) at java.util.HashMap.internalWriteEntries(HashMap.java:1793) at java.util.HashMap.writeObject(HashMap.java:1363) at sun.reflect.GeneratedMethodAccessor65.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:498) at org.jboss.marshalling.reflect.JDKSpecific$SerMethods.callWriteObject(JDKSpecific.java:156) at org.jboss.marshalling.reflect.SerializableClass.callWriteObject(SerializableClass.java:191) at org.jboss.marshalling.river.RiverMarshaller.doWriteSerializableObject(RiverMarshaller.java:1028) at org.jboss.marshalling.river.RiverMarshaller.doWriteObject(RiverMarshaller.java:920) at org.jboss.marshalling.river.RiverMarshaller.doWriteFields(RiverMarshaller.java:1082) at org.jboss.marshalling.river.RiverMarshaller.doWriteSerializableObject(RiverMarshaller.java:1040) at org.jboss.marshalling.river.RiverMarshaller.doWriteObject(RiverMarshaller.java:920) at org.jboss.marshalling.AbstractObjectOutput.writeObject(AbstractObjectOutput.java:58) at org.jboss.marshalling.AbstractMarshaller.writeObject(AbstractMarshaller.java:111) at org.jenkinsci.plugins.workflow.support.pickles.serialization.RiverWriter.lambda$writeObject$0(RiverWriter.java:144) at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.GroovySandbox.runInSandbox(GroovySandbox.java:237) at org.jenkinsci.plugins.workflow.support.pickles.serialization.RiverWriter.writeObject(RiverWriter.java:143) at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.saveProgram(CpsThreadGroup.java:523) at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.saveProgram(CpsThreadGroup.java:499) at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.saveProgramIfPossible(CpsThreadGroup.java:486) at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.run(CpsThreadGroup.java:410) at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.access$200(CpsThreadGroup.java:93) at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:282) at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:270) at org.jenkinsci.plugins.workflow.cps.CpsVmExecutorService$2.call(CpsVmExecutorService.java:66) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at hudson.remoting.SingleLaneExecutorService$1.run(SingleLaneExecutorService.java:131) at jenkins.util.ContextResettingExecutorService$1.run(ContextResettingExecutorService.java:28) at jenkins.security.ImpersonatingExecutorService$1.run(ImpersonatingExecutorService.java:59) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) at java.util.concurrent.FutureTask.run(FutureTask.java:266) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) at java.lang.Thread.run(Thread.java:748) Finished: FAILURE

Is there a better/different way to check if an item is a folder?

[ZillaYT]

Or, if it's any easier, how can I get a list of folders in a Jenkins pipeline?

[Ivan Fernandez Calvo]

See https://github.com/cloudbees/jenkins-scripts/blob/master/findStaleFolders.groovy if you make it from a pipeline you would need to approve a bunch of methods in the script approval, also you probably need to use the @NonCPS see https://wiki.jenkins.io/plugins/servlet/mobile?contentId=175211277#content/view/175211277