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 and, prepares the format name of the queue using the translated string, then 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
    }
     

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