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| JAVA - Read multi messages from a Queue with single access. |
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| kalpakci |
 Posted: Wed May 22, 2013 5:50 am Post subject: JAVA - Read multi messages from a Queue with single access. |
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Newbie
Joined: 19 Mar 2012
Posts: 3
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I'm new to Websphere MQ - Java operations. I use Java to read messages from a queue then process them.
First I connect to queue, read a single message, then disconnect. It opens and closes about 20 connections per second.
1 - How can i read more than one message per access.
2 - I use openOptions = 28. It is working but is it correct?
My running code:
| Code: |
MQMessage retrievedMessage = null;
private MQQueueManager qMgr = null;
public void run() throws InterruptedException {
Config.Get_Values();
MQQueue myQueue = null;
int openOptions = 28;
int queuedepth = 0;
com.ibm.mq.MQEnvironment.hostname = Config.MQHostname;
com.ibm.mq.MQEnvironment.port = Config.MQPort;
com.ibm.mq.MQEnvironment.channel = Config.MQchannel;
com.ibm.mq.MQEnvironment.CCSID = Config.MQCCSID;
this.qMgr = new MQQueueManager(Config.MQManagerName);
MQQueue queue_depth_access = this.qMgr.accessQueue(Config.MQQueueName, MQC.MQOO_SET | MQC.MQOO_INQUIRE);
queuedepth = queue_depth_access.getCurrentDepth();
if (queuedepth < 1) {
System.out.println("queue is empy");
queue_depth_access.close();
qMgr.disconnect();
return;
}
myQueue = this.qMgr.accessQueue(Config.MQQueueName, openOptions, null, null, null);
MQMessage myMessage = new MQMessage();
myMessage.correlationId = MQC.MQCI_NONE;
myMessage.messageId = MQC.MQMI_NONE;
myQueue.get(myMessage);
msg = myMessage.readString(myMessage.getMessageLength());
myQueue.close();
qMgr.disconnect();
if (msg.contains("PMovement")) {
//process
} else {
//nothing
}
}
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| Vitor |
| Posted: Wed May 22, 2013 6:06 am Post subject: Re: JAVA - Read multi messages from a Queue with single acce |
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Grand High Poobah
Joined: 11 Nov 2005
Posts: 26093
Location: Texas, USA
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| kalpakci wrote: |
| First I connect to queue, read a single message, then disconnect. It opens and closes about 20 connections per second. |
This is the wrong design. You should connect, do whatever queue access you need to do and then disconnect when you're done.
| kalpakci wrote: |
| 1 - How can i read more than one message per access. |
By changing the design.
| kalpakci wrote: |
| 2 - I use openOptions = 28. It is working but is it correct? |
No.
_________________
Honesty is the best policy.
Insanity is the best defence. |
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| mqjeff |
| Posted: Wed May 22, 2013 6:37 am Post subject: Re: JAVA - Read multi messages from a Queue with single acce |
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Grand Master
Joined: 25 Jun 2008
Posts: 17447
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| Vitor wrote: |
| kalpakci wrote: |
| First I connect to queue, read a single message, then disconnect. It opens and closes about 20 connections per second. |
This is the wrong design. |
You should not ask for the depth of the queue.
You should read until the get tells you there are no messages left. |
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| Vitor |
| Posted: Wed May 22, 2013 6:48 am Post subject: Re: JAVA - Read multi messages from a Queue with single acce |
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Grand High Poobah
Joined: 11 Nov 2005
Posts: 26093
Location: Texas, USA
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| mqjeff wrote: |
| Vitor wrote: |
| kalpakci wrote: |
| First I connect to queue, read a single message, then disconnect. It opens and closes about 20 connections per second. |
This is the wrong design. |
You should not ask for the depth of the queue.
You should read until the get tells you there are no messages left. |
Didn't even notice that in the code 
That's wrong as well.
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Honesty is the best policy.
Insanity is the best defence. |
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| hughson |
| Posted: Wed May 22, 2013 8:33 am Post subject: Re: JAVA - Read multi messages from a Queue with single acce |
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Padawan
Joined: 09 May 2013
Posts: 1959
Location: Bay of Plenty, New Zealand
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| kalpakci wrote: |
| I use openOptions = 28. It is working but is it correct? |
In order to help others to read your code in the future, you should avoid using numbers like this and instead use the constants MQ provides for you to use. You do this in other places in your code I see, so you are not unfamiliar with the idea.
openOptions of value 28 would be the same as adding together all these constants:-
- MQC.MQOO_INPUT_EXCLUSIVE (getting from a queue in a destructive manner with exclusive queue access)
- MQC.MQOO_BROWSE (getting from a queue in a non-destructive manner)
- MQC.MQOO_OUTPUT (putting to a queue)
So you should ask yourself, do you need all those options?
As already noted, you shouldn't need to inquire the depth of the queue, especially since all you are checking for is whether there is at least one message. Attempting to get the message will tell you the same information and you can look out for the reason code MQRC_NO_MSG_AVAILABLE which will tell you the same thing.
You should ensure you only do
| Code: |
..new MQQueueManager...
..qMgr.accessQueue... |
once at the beginning, and
| Code: |
myQueue.close();
qMgr.disconnect(); |
once at the end.
Everything else ought to go in a loop until you are given, MQRC_NO_MSG_AVAILABLE. You should also ensure you are using the ability to wait a little while for messages too.
Cheers
Morag
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Morag Hughson @MoragHughson
IBM MQ Technical Education Specialist
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| fjb_saper |
| Posted: Wed May 22, 2013 11:41 am Post subject: |
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Grand High Poobah
Joined: 18 Nov 2003
Posts: 20756
Location: LI,NY
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And you should ask yourself whether input exclusive is required or whether you could use input shared? 
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