Image Processing Reference
In-Depth Information
nORB Request message format
Two-way
flag
Op
Name
ObjectKey
Length
Request
Id
Parameters
ObjectKey
Priority
nORB Reply message format
Request Id
Status
Results
nORB Locate Request message format
Locate request Id
Corbaloc style Key
nORB Locate Reply message format
Locate Reply Id
IOR string
Profile-
n
Profile-1
nORB IOR format
Transport
address
Repository Id
ObjectKey
Priority
FIGURE .
nORB IOR and message formats.
2.3.2 Object Adapter
In standard CORBA, each server-side ORB may provide multiple object adapters []. Servant objects
register with an object adapter, which demultiplexes each client request to the appropriate servant.
Each object adapter may be associated with a set of policies, e.g., for servant threading, retention, and
lifespan[].InstandardCORBA,multipleobjectadaptersaresupportedbyeachORB.hisallows
heterogeneous object policies to be implemented in a client-server environment, which is desirable
in applications such as online banking, where each object on a server may be configured according
to preferences of the server administrator, or even the end user.
In nORB, however, there is no assumption of multiple object adapters. Instead, a single object
adapter per ORB is considered preferable for simplicity and footprint reduction. In nORB, the num-
ber of objects hosted on an embedded node is expected to be small, which reduces the need for
multiple policies and thus for multiple object adapters. Even though the resulting object adapter does
notconformtothePortableObjectAdapterspeciication,asigniicantdegreeoffootprintreduction
is achieved because of the reduced object adapter functionality.
We have also simplified the process of object registration, to free developers from writing repetitive
code as is seen in many CORBA programs. In the object adapter, we maintain a lookup table of object
IDs and pointers to servant implementation objects. he lookup table is synchronized using a Read-
ers/Writer lock. We have also consolidated object registration with other middleware initialization
functions, by moving it from the object adapter interface to the ORB interface.
2.3.3 Message Flow Architecture
The message flow architecture in nORB uses strategies and patterns similar to those in TAO. We
briefly mention the strategies we used and refer the interested reader to Ref. [], which discusses
these strategies in detail.
