Supplying a different connection pool in IBM MQ classes for Java

This example shows how to use the class com.ibm.mq.MQSimpleConnectionManager to supply a different connection pool.

This class provides basic facilities for connection pooling, and applications can use this class to customize the behavior of the pool.

Once it is instantiated, an MQSimpleConnectionManager can be specified on the MQQueueManager constructor. The MQSimpleConnectionManager then manages the connection that underlies the constructed MQQueueManager. If the MQSimpleConnectionManager contains a suitable pooled connection, that connection is reused and returned to the MQSimpleConnectionManager after an MQQueueManager.disconnect() call.

The following code fragment demonstrates this behavior:

   MQSimpleConnectionManager myConnMan=new MQSimpleConnectionManager();
   myConnMan.setActive(MQSimpleConnectionManager.MODE_ACTIVE);
   MQQueueManager qmgr=new MQQueueManager("my.qmgr.1", myConnMan);
   :
   : (do something with qmgr)
   :
   qmgr.disconnect();
   
   MQQueueManager qmgr2=new MQQueueManager("my.qmgr.1", myConnMan);
   :
   : (do something with qmgr2)
   :
   qmgr2.disconnect();
   myConnMan.setActive(MQSimpleConnectionManager.MODE_INACTIVE);

The connection that is forged during the first MQQueueManager constructor is stored in myConnMan after the qmgr.disconnect() call. The connection is then reused during the second call to the MQQueueManager constructor.

The second line enables the MQSimpleConnectionManager. The last line disables MQSimpleConnectionManager, destroying any connections held in the pool. An MQSimpleConnectionManager is, by default, in MODE_AUTO, which is described later in this section.

An MQSimpleConnectionManager allocates connections on a most-recently-used basis, and destroys connections on a least-recently-used basis. By default, a connection is destroyed if it has not been used for five minutes, or if there are more than ten unused connections in the pool. We can alter these values by calling MQSimpleConnectionManager.setTimeout().

We can also set up an MQSimpleConnectionManager for use as the default connection pool, to be used when no Connection Manager is supplied on the MQQueueManager constructor.

The following application demonstrates this:

import com.ibm.mq.*;
public class MQApp4
{
      public static void main(String []args)
      {
         MQSimpleConnectionManager myConnMan=new MQSimpleConnectionManager();
         myConnMan.setActive(MQSimpleConnectionManager.MODE_AUTO);
         myConnMan.setTimeout(3600000);
         myConnMan.setMaxConnections(75);
         myConnMan.setMaxUnusedConnections(50);
         MQEnvironment.setDefaultConnectionManager(myConnMan);
         MQApp3.main(args);
      }
}

• Ends connections that are not used for an hour
• Limits the number of connections managed by myConnMan to 75
• Limits the number of unused connections in the pool to 50
• Sets MODE_AUTO, which is the default. This means that the pool is active only if it is the default connection manager, and there is at least one token in the set of MQPoolTokens held by MQEnvironment.

The new MQSimpleConnectionManager is then set as the default connection manager.

In the last line, the application calls MQApp3.main(). This runs a number of threads, where each thread uses IBM MQ independently. These threads use myConnMan when they forge connections.