A proxy is a kind of "object reference". An object reference contains information that is used to identify a target object.
To enable clients to save references to remote objects (in a file system, for example) or exchange references to remote objects (with other application processes), DSOM must be able to externalize proxies. To "externalize a proxy" means to create a string ID for a proxy that can be used by any process to identify the remote target object. DSOM must also support the translation of string IDs back into proxies.
The DSOM Object Manager defines two methods for converting between proxies and their string IDs: somdGetIdFromObject and somdGetObjectFromId.
Here is an example client program that creates a remote "Car" object. It generates a string ID corresponding to the proxy, and saves the string ID to a file for later use.
#include <stdio.h>
#include <somd.h>
#include <Car.h>
main( )
{
Environment ev;
Car car;
string somdObjectId;
FILE* file;
SOM_InitEnvironment(&ev);
SOMD_Init(&ev);
/* create a remote Car object */
car = _somdNewObject(SOMD_ObjectMgr, &ev, "Car", "");
/* save the reference to the object */
somdObjectId = _somdGetIdFromObject(SOMD_ObjectMgr, &ev, car);
file = fopen("/u/joe/mycar", "w");
fprintf(file, "%s", somdObjectId);
...
Next is an example client program that retrieves the string ID and regenerates a valid proxy for the original remote "Car" object (assuming the remote "Car" object can still be found in the server).
...
Environment ev;
Car car;
char buffer[256];
string somdObjectId;
FILE* file;
...
/* restore proxy from its string form */
file = fopen("/u/joe/mycar", "r");
somdObjectId = (string) buffer;
fscanf(file, "%s", somdObjectId);
car = _somdGetObjectFromId(SOMD_ObjectMgr, &ev, somdObjectId);
...
Once the proxy has been regenerated, methods can be invoked on the proxy and they will be forwarded to the remote target object, as always.
Note: The somdGetIdFromObject and somdGetObjectFromId methods directly correspond to the CORBA methods ORB_object_to_string and ORB_string_to_object, defined on the ORB class.