transactions.cpp

Transactions example application.

This example illustrates how to perform transaction on objects in GizmoDistribution. A publisher client update attributes on objects using transactions and a subscriber client receive the updates in notifications.

The source code can also be found in the examples directory of the GizmoDistribution installation.

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//*****************************************************************************
// File         : transactions.cpp
// Module       : transactions
// Description  : transactions (example application)
// Author       : Anders Sandblad       
// Product      : GizmoDistribution
//      
// Copyright © 2004- Saab Training Systems AB, Sweden
//          
// NOTE:    GizmoDistribution is a toolkit used for implementing distributed 
//          objects and events in C++
//
//
// Revision History...                          
//                                  
// Who  Date    Description                     
//                                  
// XAA  040421  Created file    
//
//*****************************************************************************

// Includes
#include <stdio.h>
#include "gzBaseLibrary.h"
#include "gzDistLibrary.h"


// Common constants
static const gzString EXAMPLE_SESSION = "example";
static const gzString EXAMPLE_OBJECT = "example";


//-----------------------------------------------------------------------------

// A client that publish objects
class Publisher : public gzDistClientInterface
{
    public:

        Publisher();

        virtual ~Publisher();


    private:

        // callbacks

        gzVoid onClientTick();

        gzVoid onNewObject(gzDistObject* object, gzDistSession* session);

        gzVoid onRemoveObject(gzDistObject* object, gzDistSession* session);

        gzVoid onSystemShutdown();


    private:

        // members

        gzDistSessionPtr m_session;

        gzDistObjectPtr m_object;

        gzULong m_tickCount;

};


Publisher::Publisher()
 :  gzDistClientInterface("publisher"),
    m_tickCount(0)
{
    // initialize client
    initialize(2);

    // create and join session 
    m_session = getSession(EXAMPLE_SESSION, TRUE);
    joinSession(m_session);

    // subscribe for objects
    subscribeObjects(gzDistObject::getClassType(), m_session);

    // add  object
    addObject(new gzDistObject(EXAMPLE_OBJECT), m_session);
    
}


Publisher::~Publisher()
{
    // unsubscribe objects
    unsubscribeObjects(gzDistObject::getClassType(), m_session);

    // resign the session
    resignSession(m_session);

    // uninitialize client
    uninitialize();
}


gzVoid Publisher::onNewObject(gzDistObject* object, gzDistSession* session)
{
    if (!m_object)
    {
        m_object = object;
    }
}


gzVoid Publisher::onRemoveObject(gzDistObject* object, gzDistSession* session)
{
    if (object == m_object)
    {
        m_object = NULL;
    }
}


gzVoid Publisher::onClientTick()
{
    if (!m_object)
    {
        return;
    }

    if (m_tickCount%5 != 0)
    {
        // add and/or update attributes

        // notifications will be received on callbacks
        // onNewAttributes() for new attributes and
        // onUpdateAttributes for updated attributes
        
        gzDistTransactionPtr transaction = new gzDistTransaction;
        
        gzULong count = (gzULong)(10.0 * gzRandom() + 1.0);

        for (gzUInt i = 0; i < count; i++)
        {
            transaction->setAttributeValue(gzString(i), gzString(m_tickCount));
        }

        GZMESSAGE(GZ_MESSAGE_NOTICE, "%u attributes in update transaction", count);

        updateObject(transaction, m_object);

    }
    else
    {
        // remove attributes 

        // notification will be received on callback onRemoveAttributes()

        gzDistTransactionPtr transaction = new gzDistTransaction;
        
        gzULong count = (gzULong)(10.0 * gzRandom() + 1.0);

        for (gzUInt i = 0; i < count; i++)
        {
            transaction->setAttributeName(gzString(i));
        }

        GZMESSAGE(GZ_MESSAGE_NOTICE, "%u attributes in remove transaction", count);

        removeAttributes(transaction, m_object);

    }

    ++m_tickCount;
}


gzVoid Publisher::onSystemShutdown()
{
    // GizmoDistribution is shutting down
    // free all references to enable the library to be unloaded properly
    // it is recommended to always implement this callback
    m_object = NULL;
    m_session = NULL;   
}


//-----------------------------------------------------------------------------

// A client that subscribe for objects and attributes
class Subscriber : public gzDistClientInterface
{
    public:

        Subscriber();

        virtual ~Subscriber();


    private:

        // callbacks

        gzVoid onNewObject(gzDistObject* object, gzDistSession* session);
        
        gzVoid onRemoveObject(gzDistObject* object, gzDistSession* session);

        gzVoid onNewAttributes(const gzDistNotificationSet& attributes, gzDistObject* object, gzDistSession* session);
        
        gzVoid onUpdateAttributes(const gzDistNotificationSet& attributes, gzDistObject* object, gzDistSession* session);

        gzVoid onRemoveAttributes(const gzDistNotificationSet& attributes, gzDistObject* object, gzDistSession* session);

        gzVoid onSystemShutdown();


    private:

        // members

        gzDistSessionPtr m_session;

};


Subscriber::Subscriber()
 : gzDistClientInterface("subscriber")
{
    // initialize client
    initialize();

    // create and join session
    m_session = getSession(EXAMPLE_SESSION, TRUE);
    joinSession(m_session);

    // subscribe for objects
    subscribeObjects(gzDistObject::getClassType(), m_session);
}


Subscriber::~Subscriber()
{
    // unsubscribe objects
    unsubscribeObjects(gzDistObject::getClassType(), m_session);

    // resign the session
    resignSession(m_session);

    // uninitialize client
    uninitialize();
}


gzVoid Subscriber::onNewObject(gzDistObject* object, gzDistSession* session)
{
    GZMESSAGE(GZ_MESSAGE_NOTICE, "New object '%s' on session '%s'",
                (const char*)object->getName(), (const char*)object->getSession()->getName());
    
    // subscribe for attributes on the new object
    // notifications will be received in the onNewAttributes() and onRemoveAttributes()
    // callbacks when attributes are created or removed from this object
    subscribeAttributes(object, TRUE);
    
}


gzVoid Subscriber::onRemoveObject(gzDistObject* object, gzDistSession* session)
{
    // an object was removed
    // all subscriptions associated with the object are automatically removed

    GZMESSAGE(GZ_MESSAGE_NOTICE, "Removed object '%s' from session '%s'",
                (const char*)object->getName(), (const char*)session->getName());
}


gzVoid Subscriber::onNewAttributes(const gzDistNotificationSet& attributes, gzDistObject* object, gzDistSession* session)
{
    // attributes were added to an object

    GZMESSAGE(GZ_MESSAGE_NOTICE, "%u new attributes on object '%s' on session '%s'",
                attributes.entries(), (const char*)object->getName(), (const char*)object->getSession()->getName());


    gzDistNotificationSetIterator iter(attributes);

    gzDistNotificationData* data;

    while (data = iter())
    {
        // subscribe for updates of the attribute value
        // notifications will be received in the onUpdateAttributes() callback
        subscribeAttributeValue(data->getAttributeName(), object);
    }
    
}


gzVoid Subscriber::onRemoveAttributes(const gzDistNotificationSet& attributes, gzDistObject* object, gzDistSession* session)
{
    // attributes were removed form an object

    GZMESSAGE(GZ_MESSAGE_NOTICE, "%u removed attributes from object '%s' on session '%s'",
                attributes.entries(), (const char*)object->getName(), (const char*)object->getSession()->getName());
}


gzVoid Subscriber::onUpdateAttributes(const gzDistNotificationSet& attributes, gzDistObject* object, gzDistSession* session)
{
    // attribute values were updated

    GZMESSAGE(GZ_MESSAGE_NOTICE, "%u attributes updated on object '%s' on session '%s'",
                attributes.entries(), (const char*)object->getName(), (const char*)object->getSession()->getName());
}


gzVoid Subscriber::onSystemShutdown()
{
    // GizmoDistribution is shutting down
    // free all references to enable the library to be unloaded properly
    // it is recommended to always implement this callback
    m_session = NULL;
}


//-----------------------------------------------------------------------------

// Application entry point
int main(int argc, char* argv[])
{
    // setup default message receiver
    gzMessage::setMessageLevel(GZ_MESSAGE_NOTICE);

    // create manager and start
    gzDistManagerPtr manager = gzDistManager::getManager(TRUE);
    manager->start();

    GZMESSAGE(GZ_MESSAGE_NOTICE, "Hit return to quit!\n");

    // create publisher and subscriber
    Subscriber* subscriberA =  new Subscriber;
    gzSleep(GZ_SLEEP_SECOND);
    Publisher* publisherA =  new Publisher;


    // wait for return
    getchar();


    // delete publisher and subscriber
    delete publisherA;
    gzSleep(GZ_SLEEP_SECOND);
    delete subscriberA;


    // shut down and release manager
    manager->shutDown();
    manager = NULL;

    gzSleep(GZ_SLEEP_SECOND);

    return 0;

}

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