A Detailed Comparison of CORBA, DCOM and Java/RMI[6]

the cast to istockmarket forces the microsoft jvm to call the dcom server object's queryinterface() function to request a pointer to istockmarket. if the interface is not supported, a classcastexception is thrown. reference counting is handled automatically in java/com and the microsoft jvm takes up the responsibility of calling iunknown::addref() and java's garbage collector automatically calls iunknown::release(). once the client acquires a valid pointer to the dcom server object, it calls into its methods as though it were a local object running in the client's address space.

corba client - the corba client will first have to initialize the corba orb by making a call to orb.init(). it then instantiates a corba server object by binding to a server object's remote reference. though both inprise's visibroker and iona's orbix have a bind() method to bind and obtain a server object reference like,

stockmarket market = stockmarkethelper.bind( orb ); // this is visibroker or orbix specific

we will use the corba naming service to do the same thing so that we are compatible with any orb. we first look up a nameservice and obtain a corba object reference. we use the returned corba.object to narrow down to a naming context.

namingcontext root = namingcontexthelper.narrow( orb.resolve_initial_references("nameservice") );

we now create a namecomponent and narrow down to the server object reference by resolving the name in the naming context that was returned to us by the cosnaming (corba object services - naming) helper classes.

namecomponent[] name = new namecomponent[1] ;
name[0] = new namecomponent("nasdaq","");

stockmarket market = stockmarkethelper.narrow(root.resolve(name));

once the client has acquired a valid remote object reference to the corba server object, it can call into the server object's methods as if the server object resided in the client's address space.