CNTR0020E error during heavy load when using message-driven bean
 Technote (troubleshooting)
 
Problem(Abstract)
The following exception occurs during a heavy load on a message-driven bean (MDB):

CNTR0020E: Non-application exception occurred while processing method "method_name" on bean "BeanId(bean_name, null)". Exception data:
java.lang.NullPointerException
 
Cause
This error can be due to a fundamental programming error in an application. The error occurs when a connection object is used by a thread other than the one that created the object.. Because the connection object is a J2C object, it is transactional and must not be cached. At any given time, this resource might be given back to the resource pool to maintain resources. If the thread releases the resource, it becomes null. A separate thread that uses the cached information of the resource then receives a null pointer exception if it tries to access the resource. The connection object can be used by only the thread that creates it.
 
Resolving the problem
The application code must be changed to adhere to standard programming practice.

The ejbCreate() method of the MDB contains code to look up and create an instance of a Stateless Session bean. The ejbCreate() method of the Stateless Session bean contains the following code:

queueConnection = queueConnFactory.createQueueConnection();
queueSession = queueConnection.createQueueSession(false,
Session.AUTO_ACKNOWLEDGE);
queueConnection.start();
queueSender = queueSession.createSender(queue);
myMsg = queueSession.createMessage();


This code must be moved from the ejbCreate() method of the Stateless Session bean to the point where it is immediately required. In general, this code appears in a method that performs some type of business logic outside of the ejbCreate() method.
 
 
Cross Reference information
Segment Product Component Platform Version Edition
Application Servers Runtimes for Java Technology Java SDK
 
 


Document Information


Product categories: Software > Application Servers > Distributed Application & Web Servers > WebSphere Application Server > Java Message Service (JMS)
Operating system(s): Windows
Software version: 5.1.1
Software edition:
Reference #: 1166805
IBM Group: Software Group
Modified date: Sep 11, 2004