Description

The BonoboTransient is used to create transient objects. These objects only exist during the lifetime of the method execution of the interface they implement: they are created on demand and destroyed after the method invocation finishes.

Transient objects are an optimization useful when it is possible for a very large set of object to exist but there is no need to have implementations of the servers running all the time, as they can be created on the demand to satisfy the requests of client applications.

For example, consider the case in which a large list of objects needs to be returned to a client application. For example, an object reference could be returned for every file on a directory. But it would be wasteful to keep one server running for each file. And given that the program has all the information available to create the servers on demand, you want to use this system.

This can be used for implementations of the IDL:Bonobo/PropertyBag interface, as there are in theories thousands of keys that could be returned, but the method invocations on each object is short-lived, so it is efficient to just create servers to satisfy an object request on demand, and destroy them when the request is done.

To create such object, you first need to create a BonoboTransient object, and then for every virtual object that you want to expose to the world, you invoke the bonobo_transient_create_objref() function to create a new CORBA object reference.

bonobo_transient_new() will create a new POA inside the POA you specify (you can use CORBA_OBJECT_NIL to get the POA to be created in the default Bonobo POA). All object references created with bonobo_transient_create_objref() will live in this new POA.

The bonobo_transient_new() function takes an argument that specifies the function that will be used to create the temporary CORBA servant that will satisfy an incoming request. And a function that will be used to destroy the servant when the request processing is done.

The bonobo_transient_create_objref() function takes a number of arguments:

• The name of the object you want to create. This name will be passed to the servant creation routine when an incoming request for that object comes in. Your servant creation routine should be able to create a servant from the data you expose as the name (it can be a stringified representation of an in-process pointer for all that we care).

• The interface name implemented by the object named before. This is the CORBA interface name that your object implements, for example "IDL:Echo/echo:1.0".

Here is an example of how to use BonoboTransient:

BonoboTransient *my_transient = NULL;

static PortableServer_Servant
create_servant (PortableServer_POA  poa,
                BonoboTransient    *bt,
                char               *name,
                void               *my_callback_data)
{
        MyServant *servant;

	if (!my_validate_name (name))
        	return NULL;

        servant = g_new0 (MyServant, 1);
        servant->vepv = my_servant_get_epv();
        servant->my_data = g_strdup ("Hello world!");
        POA_My_Iface__init ((PortableServer_Servant) servant, &ev);
        return servant;
}

void
destroy_servant (PortableServer_Servant servant, void *my_callback_data)
{
        CORBA_Environment ev;

        g_free (servant->my_data);
        CORBA_exception_init (&ev);
        POA_My_Iface__fini (servant, &ev);
        CORBA_exception_free (&ev);
}

CORBA_Object
impl_Some_Iface (PortableServer_Servant servant, CORBA_Environment *ev)
{
	return bonobo_transient_create_objref (
        	my_transient, "IDL:My/Iface:1.0",
                "hello",
                ev);
}

void
init_transient()
{
	my_transient = bonobo_transient_new (
		CORBA_OBJECT_NIL,
                create_servant,
                destroy_servant,
                NULL);
}


     

The previous example shows: how the my_transient object is first created, and what the implementations for the create_servant and destroy_servant look like. It does not make use of the user pointer, so it passes NULL. However, in practice, applications will most likely want to pass data here to the new_servant and destroy_servant methods.

The impl_Some_Iface is a method that we assume in the example will be part of the implementation of a CORBA server. This method will be invoked at some time to get an object reference to one of the transient objects (in this case, we have called our object "hello" and it implements the interface IDL:My/Iface:1.0).

Details

typedef struct {
	GtkObject parent;

	BonoboTransientPriv *priv;
} BonoboTransient;

typedef struct {
	GtkObjectClass parent_class;
} BonoboTransientClass;

PortableServer_Servant (*BonoboTransientServantNew)
                                            (PortableServer_POA,
                                             BonoboTransient*,
                                             char *name,
                                             void *data);

void        (*BonoboTransientServantDestroy)
                                            (PortableServer_Servant servant,
                                             void *data);

BonoboTransient* bonobo_transient_new       (PortableServer_POA poa,
                                             BonoboTransientServantNew new_servant,
                                             BonoboTransientServantDestroy destroy_servant,
                                             void *data);

BonoboTransient* bonobo_transient_construct (BonoboTransient *transient,
                                             PortableServer_POA poa,
                                             BonoboTransientServantNew new_servant,
                                             BonoboTransientServantDestroy destroy_servant,
                                             gpointer data);

CORBA_Object bonobo_transient_create_objref (BonoboTransient *transient,
                                             const char *iface_name,
                                             const char *name,
                                             CORBA_Environment *ev);

See Also

BonoboPropertyBag