Electrical computers and digital processing systems: multicomput – Distributed data processing – Client/server
Reexamination Certificate
1997-12-18
2001-06-19
Harrell, Robert B. (Department: 2152)
Electrical computers and digital processing systems: multicomput
Distributed data processing
Client/server
C709S229000
Reexamination Certificate
active
06249803
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
The following U.S. patent applications are related to the present application and are incorporated by reference herein in their entirety:
U.S. patent application Ser. No. 08/554,794, filed Nov. 7, 1995 as a continuation to U.S. patent application Ser. No. 07/995,863, filed Dec. 21, 1992 (now abandoned);
U.S. patent application Ser. No. 08/670,682, filed Jun. 26, 1996;
U.S. patent application Ser. No. 08/673,181, filed Jun. 26, 1996;
U.S. patent application Ser. No. 08/670,700, filed Jun. 26, 1996;
U.S. patent application Ser. No. 08/670,681, filed Jun. 26, 1996;
U.S. patent application Ser. No. 08/670,684, filed Jun. 26, 1996;
U.S. patent application Ser. No. 08/669,782, filed Jun. 26, 1996;
U.S. Patent Application entitled “Method and Apparatus for Deferred Throwing of Exceptions in C++”, filed by Christian J. Callsen and Ken M. Cavanaugh, assigned attorney docket no. 6205491 and filed on an even date herewith;
U.S. Patent Application entitled “Method and Apparatus for Fast, Local CORBA Object References”, filed by Christian J. Callsen and Ken M. Cavanaugh, assigned attorney docket no. 08/993,800 and filed on an even date herewith;
U.S. Patent Application entitled “Method and Apparatus for Constructing Stable Iterators in a Shared Data Collection”, filed by Christian J. Callsen and Ken M. Cavanaugh, assigned attorney docket no. 6016489 and filed on an even date herewith;
U.S. Patent Application entitled, “Method and Apparatus for Enforcing Locking Invariants in Multi-Threaded Systems”, filed by Christian J. Callsen and Ken M. Cavanaugh, assigned attorney docket no. 08/993,206 and filed on an even date herewith;
U.S. Patent Application entitled, “Method and Apparatus for Efficient Representation of Variable Length Identifiers in a Distributed Object System”, filed by Ken M. Cavanaugh, assigned attorney docket no. 08/993,204 and filed on an even date herewith; and
U.S. Patent Application entitled, “Marshaling And Unmarshaling Framework For Supporting Filters In A Distributed Object System”, filed by Anita Jindal, Ken M. Cavanaugh and Sanjeev Krishnan, assigned attorney docket no. 08/993,263 and filed on an even date herewith.
FIELD OF THE INVENTION
This invention relates to distributed object systems using common object request broker architecture (CORBA) and, more particularly, to a method and apparatus for providing a filter framework for the execution of code during a method invocation.
BACKGROUND OF THE INVENTION
Software programs are continually becoming more complicated. Early programs consisted of straightforward procedural code that presented a simple, command line interface and text display to the user. These simple programs have gradually been replaced with complex programs that have graphical user interfaces and multiple features.
As programs have grown in complexity, the amount of effort which is required to write and debug the programs has also increased drastically. Consequently, major efforts have been made to reduce the amount of programming necessary to produce a modern, full-featured product. One of the most successful of these efforts has been the development of object-oriented programming in which programs are designed as collections of discrete elements called “objects”. The objects can be modified and re-used in many cases, thereby reducing the development effort.
As will be understood by those skilled in the art, objects in the context of object-oriented programming are software entities comprising data and methods or operations on that data. The methods of an object collectively form an interface for manipulating the data in the object. The objects exist only at program runtime and are created, or instantiated, from object “classes” which are actually written by the programmer. The class code written by a programmer can be “reused” by another programmer by instantiating objects from that code.
In order to further reduce the programming burden, distributed object systems have been developed in which methods in objects resident on a server can be executed or invoked remotely over a network from a client application. In this manner, the objects can be developed and maintained by a party different from the party that developed the client application. In such a system information is routed or streamed between the client and the server. This information includes requests from the client to invoke an object on the server and results and data from the method invocation returning from the server to the client. In addition, object-oriented programs often communicate by streaming objects from one program to another.
In such streaming operations, a stream writer organizes, or marshals, the information to form a serial data stream. The serial data stream is then sent to the server where a stream reader unmarshals the serial data stream to reconstruct a copy of the original information. The stream reader must operate such that the unmarshaling exactly “undoes” the effect of the marshaling so that the original information can be reconstructed. Ordinarily, such an operation does not present a problem, but when the stream reader is not written by the same author as the stream writer there can be incompatibilities.
In order to standardize the marshaling and unmarshaling and data transfer process, an industry consortium called the Object Management Group (OMG) was formed whose mission is to define a set of interfaces for inter-operable software. Its first specification, the Common Object Request Broker Architecture (CORBA) specification, is an industry consensus standard that hides all differences between programming languages, operating systems, and object location. The CORBA standard defines an object request broker (ORB) that handles the marshaling, transport and unmarshaling of information between applications. The ORB functions as a communication infrastructure, transparently relaying object requests across distributed heterogeneous computing environments. Inter-operability is accomplished through well-defined object interface specifications which allow client applications to connect to the ORB. CORBA provides an implementation independent notation for defining interfaces called the OMG Interface Definition Language (IDL).
The OMG CORBA specification defines an implementation independent object model which is actually built with a programming language, such as C++ or Java. In this model CORBA objects (also called “servants”), which are implemented by servers, have references that can be exported to clients. Clients and servers are roles, not mutually exclusive tasks for a single program, so that any one program can be both a client and a server. Objects and object references are typically different programming language objects, although they do not have to be.
In a server, the implementation of an actual object which can be used to satisfy an invocation on a CORBA object is generally both platform and language dependent and various models are possible for implementing objects in servers. The original CORBA standard defined a Basic Object Adapter (or BOA) which is a framework that adapts the server implementation to the implementation independent ORB. A newer OMG portability standard defines a Portable Object Adapter (or POA), which replaces the BOA and is intended to be platform independent. Many ORBs also support other proprietary frameworks for implementing CORBA objects. All of these frameworks are commonly referred to as Object Adapters (or OAs).
An application programmer using object request broker technology may want to execute code segments as a part of the method invocation process, specifically during the marshaling and unmarshaling processes. Such code segments may operate to monitor and debug a program, or to implement security mechanisms, for example. Filters, that is, sections of code which execute during the method invocation process before or after marshaling or unmarshaling of arguments in an object request broker system, are known. Filters may be used to perform a variety of tasks, such as c
Cavanaugh Ken M.
Garg Rohit
Jindal Anita
Krishnan Sanjeev
Harrell Robert B.
Kurdirks & Jobse, LLP
Sun Microsystems Inc.
Vu Thong
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