FlowableClassLoadingException: Engine looking for classes at older class path

Flowable Engine
1

Recently, I’ve changed the classpath of my Spring boot application using embedded Flowable engine version 7.0.0.M1
For example, older class path was “com.a.b.c.GetItemsWorker” (GetItemsWorker is my class)
New class path is “com.x.y.z.GetItemsWorker”
When I try to run the existing Workflow which was created before changing the class path then I get below error,
org.flowable.common.engine.api.FlowableException: couldn’t instantiate class com.a.b.c.GetItemsWorker

            at org.flowable.common.engine.impl.util.ReflectUtil.instantiate(ReflectUtil.java:139)

            at org.flowable.engine.impl.bpmn.helper.AbstractClassDelegate.defaultInstantiateDelegate(AbstractClassDelegate.java:64)

            at org.flowable.engine.impl.bpmn.helper.AbstractClassDelegate.defaultInstantiateDelegate(AbstractClassDelegate.java:75)

            at org.flowable.engine.impl.bpmn.helper.AbstractClassDelegate.instantiateDelegate(AbstractClassDelegate.java:49)

            at org.flowable.engine.impl.bpmn.helper.ClassDelegate.getActivityBehaviorInstance(ClassDelegate.java:257)

            at org.flowable.engine.impl.bpmn.helper.ClassDelegate.execute(ClassDelegate.java:190)

            at org.flowable.engine.impl.agenda.ContinueProcessOperation.executeActivityBehavior(ContinueProcessOperation.java:298)

            at org.flowable.engine.impl.agenda.ContinueProcessOperation.executeSynchronous(ContinueProcessOperation.java:175)

            at org.flowable.engine.impl.agenda.ContinueProcessOperation.continueThroughFlowNode(ContinueProcessOperation.java:125)

            at org.flowable.engine.impl.agenda.ContinueProcessOperation.run(ContinueProcessOperation.java:88)

            at org.flowable.common.engine.impl.AbstractEngineConfiguration.lambda$new$0(AbstractEngineConfiguration.java:195)

            at org.flowable.engine.impl.interceptor.CommandInvoker.executeOperation(CommandInvoker.java:130)

            at org.flowable.engine.impl.interceptor.CommandInvoker.executeOperations(CommandInvoker.java:114)

            at org.flowable.engine.impl.interceptor.CommandInvoker.execute(CommandInvoker.java:72)

            at org.flowable.engine.impl.interceptor.BpmnOverrideContextInterceptor.execute(BpmnOverrideContextInterceptor.java:26)

            at org.flowable.common.engine.impl.interceptor.TransactionContextInterceptor.execute(TransactionContextInterceptor.java:53)

            at org.flowable.common.engine.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:105)

            at org.flowable.common.spring.SpringTransactionInterceptor.lambda$execute$0(SpringTransactionInterceptor.java:57)

            at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:140)

            at org.flowable.common.spring.SpringTransactionInterceptor.execute(SpringTransactionInterceptor.java:57)

            at org.flowable.common.engine.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:30)

            at org.flowable.common.engine.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:56)

            at org.flowable.common.engine.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:51)

            at org.flowable.job.service.impl.asyncexecutor.ExecuteAsyncRunnable.executeJob(ExecuteAsyncRunnable.java:127)

            at org.flowable.job.service.impl.asyncexecutor.ExecuteAsyncRunnable.run(ExecuteAsyncRunnable.java:115)

            at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136)

            at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)

            at java.base/java.lang.Thread.run(Thread.java:840)

Caused by: org.flowable.common.engine.api.FlowableClassLoadingException: Class not found: com.a.b.c.GetItemsWorker

            at org.flowable.common.engine.impl.util.ReflectUtil.loadClass(ReflectUtil.java:89)

            at org.flowable.common.engine.impl.util.ReflectUtil.instantiate(ReflectUtil.java:136)

            ... 27 common frames omitted

Caused by: java.lang.ClassNotFoundException: com.a.b.c.GetItemsWorker

            at org.springframework.boot.web.embedded.tomcat.TomcatEmbeddedWebappClassLoader.loadClass(TomcatEmbeddedWebappClassLoader.java:72)

            at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1165)

            at java.base/java.lang.Class.forName0(Native Method)

            at java.base/java.lang.Class.forName(Class.java:467)

            at org.flowable.common.engine.impl.util.ReflectUtil.loadClass(ReflectUtil.java:328)

            at org.flowable.common.engine.impl.util.ReflectUtil.loadClass(ReflectUtil.java:70)

I’m wondering why Flowable engine is looking for older class at older class path.
Interestingly, if I update and save the existing Workflow which was causing the issue, then I Don’t get this error

Could anyone let me know what is happening?

2

Hey @Shekhar,

Most likely, you still have some running process instances using the old process definition (the one with the old class) and when they reach the service task they’ll try to load the old class. You’ll need to migrate those instances to the newer process definition.

Cheers,
Filip

3

Hey @filiphr,
Thanks a lot for your inputs, could you please also suggest where i can find these instances or provide me some examples?

4

@Shekhar I don’t know what you are using to monitor your Flowable instances. You can use the REST API or the Java API to see what is running there.

Cheers,
Filip