topic Re: java.util.ConcurrentModificationException in Alfresco Archive

java.util.ConcurrentModificationException

hardik_thakkar1 — Thu, 28 Aug 2014 04:48:18 GMT

Hello,I am getting below exception while running code from Web-app. Please help.SEVERE: Servlet.service() for servlet appServlet threw exceptionjava.util.ConcurrentModificationException at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793) at java.util.HashMap$ValueIterator.next(HashMap.

Re: java.util.ConcurrentModificationException

martin_grofcik — Thu, 28 Aug 2014 10:23:54 GMT

Hi,
exception is connected to the deployment.
Could you create jUnit test for it?

http://www.jorambarrez.be/blog/2012/09/24/how-to-write-a-unit-test/

Regards
Martin

Re: java.util.ConcurrentModificationException

hardik_thakkar1 — Tue, 30 Sep 2014 05:50:46 GMT

Thanks Martin.

I am not getting this exception every time. Sometimes it works fine.

What can be root cause of this? I can see it occurs while calling org.activiti.engine.impl.interceptor.CommandContext.flushSessions(CommandContext.java:210). Not sure how to overcome this issue.

I also tested this from standalone program, it's working fine. But getting issue while running it from container, Tomcat.

Any help much appreciated.

Re: java.util.ConcurrentModificationException

hardik_thakkar1 — Tue, 30 Sep 2014 10:49:27 GMT

Adding more logs..

INFO : org.springframework.beans.factory.xml.XmlBeanDefinitionReader - Loading XML bean definitions from class path resource [activiti.cfg.xml]
INFO : org.activiti.engine.impl.ProcessEngineImpl - ProcessEngine default created
INFO : org.activiti.engine.impl.jobexecutor.JobExecutor - Starting up the JobExecutor[org.activiti.engine.impl.jobexecutor.DefaultJobExecutor].
INFO : org.activiti.engine.impl.jobexecutor.AcquireJobsRunnable - JobExecutor[org.activiti.engine.impl.jobexecutor.DefaultJobExecutor] starting to acquire jobs
Event received: ENGINE_CREATED
INFO : org.activiti.engine.impl.bpmn.deployer.BpmnDeployer - Processing resource FinancialReportProcess.bpmn20.xml
Event received: ENTITY_CREATED
Event received: ENTITY_INITIALIZED
Event received: ACTIVITY_STARTED
Event received: ACTIVITY_COMPLETED
Event received: SEQUENCEFLOW_TAKEN
Event received: ACTIVITY_STARTED
Event received: ENTITY_CREATED
Event received: ENTITY_INITIALIZED
Event received: ENTITY_CREATED
Event received: ENTITY_INITIALIZED
Event received: TASK_CREATED
30-Sep-2014 16:14:20 org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet appServlet threw exception
java.util.ConcurrentModificationException
at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793)
at java.util.HashMap$ValueIterator.next(HashMap.java:822)
at org.activiti.engine.impl.interceptor.CommandContext.flushSessions(CommandContext.java:210)
at org.activiti.engine.impl.interceptor.CommandContext.close(CommandContext.java:137)
at org.activiti.engine.impl.interceptor.CommandContextInterceptor.execute(CommandContextInterceptor.java:66)
at org.activiti.engine.impl.interceptor.LogInterceptor.execute(LogInterceptor.java:31)
at org.activiti.engine.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:40)
at org.activiti.engine.impl.cfg.CommandExecutorImpl.execute(CommandExecutorImpl.java:35)
at org.activiti.engine.impl.RuntimeServiceImpl.startProcessInstanceByKey(RuntimeServiceImpl.java:69)
at com.rbos.marketrisk.service.impl.WFManagementServiceImpl.initiateWorkflow(WFManagementServiceImpl.java:18)
at com.rbos.marketrisk.controllers.WFManagementController.initiateWorkflow(WFManagementController.java:43)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:214)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:132)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:748)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:689)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:945)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:876)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:931)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:822)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)

Re: java.util.ConcurrentModificationException

martin_grofcik — Tue, 30 Sep 2014 19:37:10 GMT

Hi,

It seems that another thread has modified sessions map concurrently. (I think that I have read related topic on this forum already some time ago - try to search for it).

Regards
Martin

Re: java.util.ConcurrentModificationException

hardik_thakkar1 — Wed, 01 Oct 2014 05:26:00 GMT

Thanks Martin.

While debugging Activiti code I found that there is one daemon thread which calls repeatedly and it flushes session by calling CommandContext. So It seems that this is the thing which is creating issue.

Shall I modify Activiti code for method flushSessions() by making it synchronized? Please suggest me possible workaround as it's road blocker for my project.

Just to give you idea about what we are trying to achieve, we are developing our own REST wrapper using activiti.jar which will be used by our clients. We are using Tomcat as container.

Re: java.util.ConcurrentModificationException

hardik_thakkar1 — Wed, 01 Oct 2014 05:33:47 GMT

How can we make context reusable? I can see every time it tries to flush sessions. I want to flush them once context is destroyed. Is there any configuration for making context as reusable? Please suggest.