Research And Implementation Of CORBA Reflection Mechanism To Obtain Interface Metadata Information

Developing distributed application has to due to three major problems: complexity, heterogeneity and dynamic character. Middleware addresses the first two problems to some extent by hiding the underlying details of interprocess communication and the heterogeneities of platforms, networks and operating systems. At present, distributed application is not only in the static LAN but in dynamic condition more frequently. The problems with dynamic character are becoming more than before. Traditional middleware is lack in flexibility and adaptability because it uses a"black-box"paradigm and encapsulates details of implementation, so it is limited its ability in solving the third problem above. Therefore, researchers apply reflection technique to middleware. That is reflective middleware. It solves the third problem to some extent for the ability to check and adjust behavior of system by using opening implement and causally connected self-representation.CORBA is one of the current middleware technologies. Due to the proliferation of different middleware technologies, the need to integrate disparate middleware systems is becoming more common. The key thing in integrating CORBA systems with other systems is metadata. Interface Repository (IFR) is the only standard way to obtain metadata for dynamic CORBA. However it has disadvantages, such as its own complexity, needing additional resource in running and easily going to stale. These limit CORBA to integrate with non-CORBA systems. This promotes CORBA reflection with XML. It solves the problem of IFR by allowing an application to ask an object for its interface metadata easily.In this paper, we do extent and deep studies in the center CORBA reflection. Firstly analysis the reflection technique including definition, opening feature, causal connection, character and class, study reification and Meta-Object Protocol (MOP) and study the use of reflection in Java and Object Oriented Programming (OOP) .Then study and analysis reflective middleware, discuss the key techniques in reflective middleware such as reflective, design of MOP and keeping consistency and class the current reflective middleware projects, especially introduce a few typical CORBA reflective middleware projects. Thirdly, analysis the possibility of getting metadata not using IFR in CORBA, and study and design CORBA reflection mechanism with XML including how to get information of interface and how to format the metadata to XML document according IFR XMLSchema specification. At last, implement an original system of this mechanism including IFRProvider operation to get metadata and XMLFormatter operation to format metadata, and test and certify the system using a simple case. The original system supports opening implement in interface definition level. Client can obtain metadata information easily.