Introduction To Corba
- 1. Introduction to CORBA Course Outline Distributed Applications Data are Distributed Computation is Distributed Users are Distributed Fundamental Realities of Distributed Systems Distributed Object Systems What is CORBA? The OMG CORBA Architecture The ORB CORBA as a Standard for Distributed Objects CORBA Services CORBA Products The Stock Application Some Objects in the Stock Application Implementing a CORBA Client CORBA Objects are Described by IDL Interfaces Object References and Requests IDL Type System IDL Type Operations Request Type Checking IDL to Java Binding
- 2. IDL to Java Compiler Obtaining Object References The Client's Model of Object Creation Exceptions Object Implementations Providing an Implementation Interface versus Implementation Hierarchies Implementation Type Checking Implementing a Server Using the Java 2 ORB Implementing a Server Using VisiBroker 3.x Differences Between Server Implementations Packaging Object Implementations Object Adapters Activation on Demand by the Basic Object Adapter (BOA) Portable Object Adapter (POA) Resources Web Sites Documentation and Specs Books Miscellaneous About The Java 2 ORB idltojava Notes System Properties VisiBroker 3.x
- 3. VisiBroker Tools Using VisiBroker with Java 2 Portable Stubs and Skeletons Using the BOA with VisiBroker Using the VisiBroker Smart Agent Distributed Applications CORBA products provide a framework for the development and execution of distributed applications. But why would one want to develop a distributed application in the first place? As you will see later, distribution introduces a whole new set of difficult issues. However, sometimes there is no choice; some applications by their very nature are distributed across multiple computers because of one or more of the following reasons: The data used by the application are distributed The computation is distributed The users of the application are distributed Data are Distributed Some applications must execute on multiple computers because the data that the application must access exist on multiple computers for administrative and ownership reasons. The owner may permit the data to be accessed remotely but not stored locally. Or perhaps the data cannot be co-located and must exist on multiple heterogeneous systems for historical reasons. Computation is Distributed Some applications execute on multiple computers in order to take advantage of multiple processors computing in parallel to solve some problem. Other applications may execute on multiple computers in order to take advantage of some unique feature of a particular system. Distributed applications can take advantage of the scalability and heterogeneity of the distributed system. Users are Distributed Some applications execute on multiple computers because users of the application communicate and interact with each other via the application. Each user executes a piece of the distributed application on his or her computer, and shared objects, typically execute on one or more servers. A typical architecture for this kind of application is illustrated below.
- 4. Prior to designing a distributed application, it is essential to understand some of the fundamental realities of the distributed system on which it will execute. Fundamental Realities of Distributed Systems Distributed application developers must address a number of issues that can be taken for granted in a local program where all logic executes in the same operating system process. The following table summarizes some of the basic differences between objects that are co-located in the same process, and objects that interact across process or machine boundaries.
- 5. Co-located Distributed Communication Fast Slow Failures Objects fail together Objects fail separately Network can partition Concurrent access Only with multiple threads Yes Secure Yes No The