exception EJB is already associated with an incomplete transaction

when I invoke list page I get this error ,also program running but some progresses arent working and redirect debug page ,I couldnt fix it ,anybody know this error,what does it mean

INFO: EJB5018: An exception was thrown during an ejb invocation on [EjbSynchronization开发者_如何转开发s] INFO: javax.ejb.EJBException: nested exception is: java.lang.IllegalStateException: EJB is already associated with an incomplete transaction java.lang.IllegalStateException: EJB is already associated with an incomplete transaction com.sun.enterprise.web.PESessionLockingStandardPipeline.invoke(PESessionLockingStandardPipeline.java:98) //lots of useless error info

The error means that two threads are attempting to call the same stateful session bean instance. A stateful session bean instance can only be associated with a single transaction (which are per thread) at a time. Without more information, it's impossible to know what is wrong with the application to make this happen. One possibility is that the application injects a stateful session bean into a servlet, so all requests on all threads are attempting to use the same instance. Either each request should create its own instance of the bean, or the bean should actually be stateless.