IT07964: WMQ MULTITHREADED JAVA APPLICATION THROWS NULLPOINTEREXCEPTION WHEN USING CCDT

APAR status

• Closed as program error.

Error description

• A WebSphere MQ classes for Java application throws a
  java.lang.NullPointerException when two (or more) threads
  attempt to establish a connection to WebSphere MQ using the same
  CCDT URL. The stack of the exception is:
  
  java.lang.NullPointerException
   at
  com.ibm.mq.jmqi.remote.internal.RemoteFAP.jmqiConnect(RemoteFAP.
  java:1697)
   at
  com.ibm.mq.jmqi.remote.internal.RemoteFAP.jmqiConnect(RemoteFAP.
  java:1305)
   at com.ibm.mq.MQSESSION.MQCONNX_j(MQSESSION.java:924)
   at
  com.ibm.mq.MQManagedConnectionJ11.(MQManagedConnectionJ11.
  java:233)
   at
  com.ibm.mq.MQClientManagedConnectionFactoryJ11._createManagedCon
  nection(MQClientManagedConnectionFactoryJ11.java:487)
   at
  com.ibm.mq.MQClientManagedConnectionFactoryJ11.createManagedConn
  ection(MQClientManagedConnectionFactoryJ11.java:529)
   at
  com.ibm.mq.StoredManagedConnection.(StoredManagedConnectio
  n.java:96)
   at
  com.ibm.mq.MQSimpleConnectionManager.allocateConnection(MQSimple
  ConnectionManager.java:208)
   at
  com.ibm.mq.MQQueueManagerFactory.obtainBaseMQQueueManager(MQQueu
  eManagerFactory.java:882)
   at
  com.ibm.mq.MQQueueManagerFactory.procure(MQQueueManagerFactory.j
  ava:772)
   at
  com.ibm.mq.MQQueueManagerFactory.constructQueueManager(MQQueueMa
  nagerFactory.java:723)
   at
  com.ibm.mq.MQQueueManagerFactory.createQueueManager(MQQueueManag
  erFactory.java:173)
   at
  com.ibm.mq.MQQueueManager.(MQQueueManager.java:1066)
   ... ...
  

Local fix

• Do not share a CCDT file across multiple threads.
  
  For example, if using the WebSphere MQ classes for Java, you can
  pass the CCDT file as a URL value on the constructor of the
  class:
  
  com.ibm.mq.MQQueueManager(
          java.lang.String queueManagerName,
          java.util.Hashtable properties,
          java.net.URL url
  )
  
  If you copy the CCDT file to a new file for each new thread
  which is creating the MQQueueManager object, and pass that new
  file URL into each contructor's argument, the problem is worked
  around.
  

Problem summary

• ****************************************************************
  USERS AFFECTED:
  This issue affects users of the WebSphere MQ classes for JMS or
  classes for Java who create multiple connections to WebSphere MQ
  using the same CCDT file.
  
  
  Platforms affected:
  MultiPlatform
  
  ****************************************************************
  PROBLEM DESCRIPTION:
  A timing windows existed in the WebSphere MQ classes for JMS and
  classes for Java whereby two threads could share and manipulate
  the same MQCD structure, parsed from a CCDT file. This resulted
  in the following processing:
  
  
  Thread 1:
      Check Property A on the MQCD object is not null.
  
  Thread 2:
      Check Property A on the MQCD object is not null.
  
  Thread 1:
      Perform some action on Property A from the MQCD object
  
  Thread 1:
      Set Property A on the MQCD object to null.
  
  Thread 2:
      Perform some action on Property A from the MQCD object.
  
  
  The last in the above steps resulted in a
  java.lang.NullPointerException to be thrown on Thread 2, because
  Thread 1 set the MQCD property to null between Thread 2 having
  checked whether the property was null and then performing some
  action on it.
  

Problem conclusion

• The WebSphere MQ classes for JMS and classes for Java have been
  updated such that each thread creates a copy of the MQCD object,
  parsed from a shared CCDT file, to use when establishing a
  connection to WebSphere MQ.
  
  ---------------------------------------------------------------
  The fix is targeted for delivery in the following PTFs:
  
  Version    Maintenance Level
  v7.0       7.0.1.14
  v7.1       7.1.0.7
  v7.5       7.5.0.6
  v8.0       8.0.0.4
  
  The latest available maintenance can be obtained from
  'WebSphere MQ Recommended Fixes'
  http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006037
  
  If the maintenance level is not yet available information on
  its planned availability can be found in 'WebSphere MQ
  Planned Maintenance Release Dates'
  http://www-1.ibm.com/support/docview.wss?rs=171&uid=swg27006309
  ---------------------------------------------------------------
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  WMQ WINDOWS V7

• Fixed component ID

  5724H7220

Applicable component levels

• R701 PSY

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