Supplying your own ConnectionManager

 

Under Java™ 2 v1.3, with JAAS 1.0 installed, applications and middleware providers can provide alternative implementations of connection pools. WebSphere MQ base Java provides a partial implementation of the J2EE Connector Architecture. Implementations of javax.resource.spi.ConnectionManager can either be used as the default Connection Manager or be specified on the MQQueueManager constructor.

WebSphere MQ base Java complies with the Connection Management contract of the J2EE Connector Architecture. Read this section in conjunction with the Connection Management contract of the J2EE Connector Architecture (refer to Sun's Web site at http://java.sun.com).

The ConnectionManager interface defines only one method:

package javax.resource.spi;
public interface ConnectionManager {
      Object allocateConnection(ManagedConnectionFactory mcf,
                                ConnectionRequestInfo cxRequestInfo);
}

The MQQueueManager constructor calls allocateConnection on the appropriate ConnectionManager. It passes appropriate implementations of ManagedConnectionFactory and ConnectionRequestInfo as parameters to describe the connection required.

The ConnectionManager searches its pool for a javax.resource.spi.ManagedConnection object that has been created with identical ManagedConnectionFactory and ConnectionRequestInfo objects. If the ConnectionManager finds any suitable ManagedConnection objects, it creates a java.util.Set that contains the candidate ManagedConnections. Then, the ConnectionManager calls the following:

ManagedConnection mc=mcf.matchManagedConnections(connectionSet, subject, 
cxRequestInfo);

The WebSphere MQ implementation of ManagedConnectionFactory ignores the subject parameter. This method selects and returns a suitable ManagedConnection from the set, or returns null if it does not find a suitable ManagedConnection. If there is not a suitable ManagedConnection in the pool, the ConnectionManager can create one by using:

ManagedConnection mc=mcf.createManagedConnection(subject, cxRequestInfo);

Again, the subject parameter is ignored. This method connects to a WebSphere MQ queue manager and returns an implementation of javax.resource.spi.ManagedConnection that represents the newly-forged connection. Once the ConnectionManager has obtained a ManagedConnection (either from the pool or freshly created), it creates a connection handle using:

Object handle=mc.getConnection(subject, cxRequestInfo);

This connection handle can be returned from allocateConnection().

A ConnectionManager must register an interest in the ManagedConnection through:

mc.addConnectionEventListener()

The ConnectionEventListener is notified if a severe error occurs on the connection, or when MQQueueManager.disconnect() is called. When MQQueueManager.disconnect() is called, the ConnectionEventListener can do either of the following:

• Reset the ManagedConnection using the mc.cleanup() call, then return the ManagedConnection to the pool

• Destroy the ManagedConnection using the mc.destroy() call

If the ConnectionManager is the default ConnectionManager, it can also register an interest in the state of the MQEnvironment-managed set of MQPoolTokens. To do so, first construct an MQPoolServices object, then register an MQPoolServicesEventListener object with the MQPoolServices object:

MQPoolServices mqps=new MQPoolServices();
mqps.addMQPoolServicesEventListener(listener);

The listener is notified when an MQPoolToken is added or removed from the set, or when the default ConnectionManager changes. The MQPoolServices object also provides a way to query the current size of the set of MQPoolTokens.

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