Reading Messages in a Queue Journal

The functions used to read messages in a queue journal are the same as those used to read messages in other queues. The only difference is that the format name used to open the queue journal has a special format.

    To read messages in a queue journal

1. Obtain the queue journal's format name.

   wsprintf( wszFormatNameBuffer,
             L"%s;JOURNAL",
             QueueFormatName
             );     
       

2. Call MQOpenQueue to open the queue with receive access.

   QUEUEHANDLE hQueue;
   hr= MQOpenQueue(
       wszFormatNameBuffer,
       MQ_RECEIVE_ACCESS,
       0,
       &hQueue
       );
   if (FAILED(hr))
   {
    //  Handle failure
   }
       

3. Specify the message properties to be retrieved.

   MQMSGPROPS MsgProps;
   MQPROPVARIANT aVariant[10];
   MSGPROPID aPropId[10];
   DWORD PropIdCount = 0;
   #define MSG_BODY_LEN    500
   unsigned char ucMsgBody[MSG_BODY_LEN];
   DWORD dwAppspecificIndex;
       
   // Set the PROPID_M_BODY property.
   aPropId[PropIdCount] = PROPID_M_BODY;             //PropId
   aVariant[PropIdCount].vt = VT_VECTOR|VT_UI1;      //Type
   aVariant[PropIdCount].caub.cElems = MSG_BODY_LEN; //Value
   aVariant[PropIdCount].caub.pElems = ucMsgBody;
   PropIdCount++;
       
   // Set the MQMSGPROPS structure
   MsgProps.cProp = PropIdCount;       //Number of properties.
   MsgProps.aPropID = aPropId;         //Ids of properties.
   MsgProps.aPropVar = aVariant;       //Values of properties.
   MsgProps.aStatus  = NULL;           //No Error report.
       

4. Call MQReceiveMessage to read the first message in the queue.

   hr = MQReceiveMessage(
        hQueue,              // handle to the Queue.
        5 * 60 * 1000,       // Max time (msec) to wait for msg.
        MQ_ACTION_RECEIVE,   // Action.
        &MsgProps,           // properties to retrieve.
        NULL,                // No overlapped structure.
        NULL,                // No callback function.
        NULL,                // NO cursor.
        NULL                 // No transaction.
       );
       

Example

This example reads the first message in the queue journal. It takes the queue's identifier (GUID), translates it into a string, prepares the format name of the queue using the translated string, and opens the queue and reads the first message.

HRESULT hr;
#define FORMAT_NAME_LEN 80
WCHAR wszFormatNameBuffer[ FORMAT_NAME_LEN];
DWORD dwFormatLen = FORMAT_NAME_LEN;


wsprintf( wszFormatNameBuffer,
      L"%s;JOURNAL",
      QueueFormatName
      );     
    
///////////////////////////////////
// Open queue with receive access.
///////////////////////////////////

QUEUEHANDLE hQueue;
hr= MQOpenQueue(
    wszFormatNameBuffer,
    MQ_RECEIVE_ACCESS,
    0,
    &hQueue
    );
if (FAILED(hr))
{
 //  Handle failure
}


///////////////////////////////////
// Specify the message properties 
// you want to receive.
///////////////////////////////////

MQMSGPROPS MsgProps;
MQPROPVARIANT aVariant[10];
MSGPROPID aPropId[10];
DWORD PropIdCount = 0;
#define MSG_BODY_LEN    500
unsigned char ucMsgBody[MSG_BODY_LEN];
DWORD dwAppspecificIndex;

// Set the PROPID_M_BODY property.
aPropId[PropIdCount] = PROPID_M_BODY;             //PropId
aVariant[PropIdCount].vt = VT_VECTOR|VT_UI1;      //Type
aVariant[PropIdCount].caub.cElems = MSG_BODY_LEN; //Value
aVariant[PropIdCount].caub.pElems = ucMsgBody;
PropIdCount++;

// Set the MQMSGPROPS structure
MsgProps.cProp = PropIdCount;       //Number of properties.
MsgProps.aPropID = aPropId;         //Ids of properties.
MsgProps.aPropVar = aVariant;       //Values of properties.
MsgProps.aStatus  = NULL;           //No Error report.


//////////////////////////
// Read a message.
//////////////////////////

hr = MQReceiveMessage(
     hQueue,              // handle to the Queue.
     5 * 60 * 1000,       // Max time (msec) to wait for msg.
     MQ_ACTION_RECEIVE,   // Action.
     &MsgProps,           // properties to retrieve.
     NULL,                // No overlapped structure.
     NULL,                // No callback function.
     NULL,                // NO cursor.
     NULL                 // No transaction.
    );
if (FAILED(hr))
{
 //Handle failure
}