Dequeuing Messages

This topic includes examples for dequeuing RAW (string of characters) and user-defined type messages.

Note: For more information about sample code, see Sample Code and Applications.

Dequeuing RAW (string of characters) Messages:

#include <oracl.h>

OSession osess ;

int DequeueRaw();

int main(int argc, char **argv)

{

int retVal = 0;

OStartup(OSTARTUP_MULTITHREADED);

try

{

osess.Open();

if ( ! osess.IsOpen() )

{

cout << "Session not opened: Error: " << osess.GetErrorText() << endl;

osess.Close();

OShutdown();

return -1;

}

retVal = DequeueRaw();

}

catch(OException oerr)

{

cout << "Exception while dequeuing message : " << oerr.GetErrorText() << endl;

retVal = -1;

}

OShutdown();

return retVal;

}

// This function dequeues a message of default

// type (string of characters) from the raw_msg_queue.

// Gets the message priority after dequeuing

// Checks if any message with correlation like 'AQ' is available

// on the queue.

int DequeueRaw()

{

ODatabase odb;

OAQ oaq;

OAQMsg oaqmsg;

OValue msg;

const char *msgid = 0;

odb.Open(osess, "ExampleDB", "SCOTT", "TIGER");

// Open the 'raw_msg_queue'

oaq.Open(odb,"raw_msg_queue");

// Get an instance of the default message(of RAW type)

oaqmsg.Open(oaq);

// Dequeue a message

msgid = oaq.Dequeue();

// Retrieve the message attributes

oaqmsg.GetValue(&msg);

const char *msgval = msg;

cout <<"Message '"<<msgval<<"' dequeued at priority : "<<oaqmsg.GetPriority()<<endl;

// Dequeue message with correlation like "AQ"

oaq.SetCorrelate("%AQ%");

oaq.SetDequeueMode(OAQ_DQ_REMOVE);

msgid = oaq.Dequeue();

// Retrieve the message attributes

char msgval[101];

long len = oaqmsg.GetValue(msgval,100);

msgval[len] = '\0';

cout<<"Message '"<<msgval<<"' dequeued at priority : "<<oaqmsg.GetPriority()<<endl;

//Close all of the objects

oaqmsg.Close();

oaq.Close();

odb.Close();

return 0;

}

Dequeuing User-Defined Type Messages:

// This function dequeues a message of user-defined type MESSAGE_TYPE

// from the msg_queue.

// Gets the message priority after dequeuing

// Checks if any message with correlation like 'SCOTT' is available on the queue.

int DequeueObject()

{

ODatabase odb;

OAQ oaq;

OAQMsg oaqmsg;

const char *msgid = 0;

OValue msg;

char subject[255];

char text[255];

odb.Open(osess, "ExampleDB", "SCOTT", "TIGER");

// Open the 'msg_queue'

oaq.Open(odb,"msg_queue");

// Get an instance of the udt MESSAGE_TYPE (check out schema for details)

oaqmsg.Open(oaq, OTYPE_OBJECT, "MESSAGE_TYPE");

// Dequeue message with correlation like "SCOTT"

oaq.SetCorrelate("%SCOTT%");

oaq.SetDequeueMode(OAQ_DQ_REMOVE);

msgid = oaq.Dequeue();

// Retrieve the message attributes

// Get the subject,text attributes of the message

OObject msgval;

oaqmsg.GetValue(&msgval);

msgval.GetAttrValue("subject", subject,255);

msgval.GetAttrValue("text", text,255);

cout<<"Message '"<<(subject ? subject :"")<<"' & Body : '"<<text<<"' dequeued at priority : "<<oaqmsg.GetPriority()<<endl;

msgid = 0;

oaq.SetNavigation(OAQ_DQ_FIRST_MSG);

oaq.SetCorrelate("");

// Dequeue a message

msgid = oaq.Dequeue();

// Retrieve the message attributes

OObject msgval;

oaqmsg.GetValue(&msg);

msgval = msg;

// Get the subject,text attributes of the message

msgval.GetAttrValue("subject", subject,255);

msgval.GetAttrValue("text", text,255);

cout<<"Message '"<<(subject ? subject :"")<<"' & Body : '"<<text<<"' dequeued at priority : "<<oaqmsg.GetPriority()<<endl;

// Close all of the objects

oaqmsg.Close();

oaq.Close();

odb.Close();

return 0;

}