Java MQ Code to Clear a Queue of Messages

If you have done the following runmqsc command to clear a queue:

CLEAR QLOCAL( {QueueName} )

And you wanted to do the same thing via a program, here is a fully functioning Java MQ example that will connect to a remote queue manager, issue a PCF “Clear Queue” command, get the PCF response messages and output if the PCF command was successful or not. You can download the source code from here.

Note: The PCF “Clear Queue” command will fail if an application has the queue open.

For more information about the PCF “Clear Queue” command, go to MQ KnowLedge Center here.

import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.Hashtable;

import com.ibm.mq.MQException;
import com.ibm.mq.MQQueueManager;
import com.ibm.mq.constants.CMQC;
import com.ibm.mq.constants.CMQCFC;
import com.ibm.mq.constants.MQConstants;
import com.ibm.mq.headers.MQDataException;
import com.ibm.mq.headers.pcf.PCFMessage;
import com.ibm.mq.headers.pcf.PCFMessageAgent;

/**
 * Program Name
 *  MQClearQueue01
 *
 * Description
 *  This java class issues a PCF "Clear Q" command for a queue to delete all messages 
 *  in the queue of a remote queue manager.
 *    
 *  Note: The PCF "Clear Q" command will fail if an application has the queue open.
 *
 * Sample Command Line Parameters
 *  -m MQA1 -h 127.0.0.1 -p 1414 -c TEST.CHL -q TEST.Q1 -u UserID -x Password
 *
 * @author Roger Lacroix
 */
public class MQClearQueue01
{
   private static final SimpleDateFormat  LOGGER_TIMESTAMP = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss.SSS");

   private Hashtable<String,String> params;
   private Hashtable<String,Object> mqht;

   public MQClearQueue01()
   {
      super();
      params = new Hashtable<String,String>();
      mqht = new Hashtable<String,Object>();
   }

   /**
    * Make sure the required parameters are present.
    * @return true/false
    */
   private boolean allParamsPresent()
   {
      boolean b = params.containsKey("-h") && params.containsKey("-p") &&
                  params.containsKey("-c") && params.containsKey("-m") &&
                  params.containsKey("-q") &&
                  params.containsKey("-u") && params.containsKey("-x");
      if (b)
      {
         try
         {
            Integer.parseInt((String) params.get("-p"));
         }
         catch (NumberFormatException e)
         {
            b = false;
         }
      }

      return b;
   }

   /**
    * Extract the command-line parameters and initialize the MQ HashTable.
    * @param args
    * @throws IllegalArgumentException
    */
   private void init(String[] args) throws IllegalArgumentException
   {
      int port = 1414;
      if (args.length > 0 && (args.length % 2) == 0)
      {
         for (int i = 0; i < args.length; i += 2)
         {
            params.put(args[i], args[i + 1]);
         }
      }
      else
      {
         throw new IllegalArgumentException();
      }

      if (allParamsPresent())
      {
         try
         {
            port = Integer.parseInt((String) params.get("-p"));
         }
         catch (NumberFormatException e)
         {
            port = 1414;
         }

         mqht.put(CMQC.CHANNEL_PROPERTY, params.get("-c"));
         mqht.put(CMQC.HOST_NAME_PROPERTY, params.get("-h"));
         mqht.put(CMQC.PORT_PROPERTY, new Integer(port));
         mqht.put(CMQC.USER_ID_PROPERTY, params.get("-u"));
         mqht.put(CMQC.PASSWORD_PROPERTY, params.get("-x"));

         // I don't want to see MQ exceptions at the console.
         MQException.log = null;
      }
      else
      {
         throw new IllegalArgumentException();
      }
   }

   /**
    * Handle connecting to the queue manager, issuing PCF command then
    * looping through PCF response messages and disconnecting from
    * the queue manager.
    */
   private void doPCF()
   {
      MQQueueManager  qMgr   = null;
      PCFMessageAgent agent  = null;
      PCFMessage   request   = null;
      PCFMessage[] responses = null;
      String qMgrName  = (String) params.get("-m");
      String queueName = (String) params.get("-q");

      try
      {
         qMgr = new MQQueueManager(qMgrName, mqht);
         MQClearQueue01.logger("successfully connected to "+ qMgrName);

         agent = new PCFMessageAgent(qMgr);
         MQClearQueue01.logger("successfully created agent");

         // https://www.ibm.com/docs/en/ibm-mq/latest?topic=formats-clear-queue
         request = new PCFMessage(CMQCFC.MQCMD_CLEAR_Q);

         request.addParameter(CMQC.MQCA_Q_NAME, queueName);

         responses = agent.send(request);

         MQClearQueue01.logger("responses.length="+responses.length);

         for (int i = 0; i < responses.length; i++)
         {
            if ((responses[i]).getCompCode() == CMQC.MQCC_OK)
               MQClearQueue01.logger("Successfully cleared queue '"+queueName+"' of messages.");
            else
               MQClearQueue01.logger("Error: Failed to clear queue '"+queueName+"' of messages.");
         }
      }
      catch (MQException e)
      {
         MQClearQueue01.logger("CC=" +e.completionCode + " : RC=" + e.reasonCode + " [" + MQConstants.lookup(e.reasonCode, "MQRC_.*") + "]");
      }
      catch (IOException e)
      {
         MQClearQueue01.logger("IOException:" +e.getLocalizedMessage());
      }
      catch (MQDataException e)
      {
         if ( (e.completionCode == CMQC.MQCC_FAILED) && (e.reasonCode == CMQCFC.MQRCCF_OBJECT_OPEN) )
            MQClearQueue01.logger("Error: Failed to clear queue '"+queueName+"' of messages. An application has the queue open.");
         else
            MQClearQueue01.logger("CC=" +e.completionCode + " : RC=" + e.reasonCode + " [" + MQConstants.lookup(e.reasonCode, "MQRC_.*") + "]");
      }
      finally
      {
         try
         {
            if (agent != null)
            {
               agent.disconnect();
               MQClearQueue01.logger("disconnected from agent");
            }
         }
         catch (MQDataException e)
         {
            MQClearQueue01.logger("CC=" +e.completionCode + " : RC=" + e.reasonCode + " [" + MQConstants.lookup(e.reasonCode, "MQRC_.*") + "]");
         }

         try
         {
            if (qMgr != null)
            {
               qMgr.disconnect();
               MQClearQueue01.logger("disconnected from "+ qMgrName);
            }
         }
         catch (MQException e)
         {
            MQClearQueue01.logger("CC=" +e.completionCode + " : RC=" + e.reasonCode + " [" + MQConstants.lookup(e.reasonCode, "MQRC_.*") + "]");
         }
      }
   }

   /**
    * A simple logger method
    * @param data
    */
   public static void logger(String data)
   {
      String className = Thread.currentThread().getStackTrace()[2].getClassName();

      // Remove the package info.
      if ( (className != null) && (className.lastIndexOf('.') != -1) )
         className = className.substring(className.lastIndexOf('.')+1);

      System.out.println(LOGGER_TIMESTAMP.format(new Date())+" "+className+": "+Thread.currentThread().getStackTrace()[2].getMethodName()+": "+data);
   }

   public static void main(String[] args)
   {
      MQClearQueue01 mqcq = new MQClearQueue01();

      try
      {
         mqcq.init(args);
         mqcq.doPCF();
      }
      catch (IllegalArgumentException e)
      {
         MQClearQueue01.logger("Usage: java MQClearQueue01 -m QueueManagerName -h host -p port -c channel -q QueueName -u UserID -x Password");
         System.exit(1);
      }

      System.exit(0);
   }
}

Regards,
Roger Lacroix
Capitalware Inc.