Research On The Relational-object Mapping And Pooled Resources Based On The NCCS Database Middleware

With the growing of database application development, applications are becoming more and more in-depth and complex. In order to solve the unification of heterogeneous database access, to achieve the integration of distributed data and to provide functional unified data applications, resulting in the Database Middleware.The Navy Combat Command System (NCCS) Database Middleware is a Persistence Framework applying the Object-relational Mapping (ORM) technology providing a persistence solution for the C++ database application. Differently with the Traditional database middleware, it applies the object-relational mapping technology, and has real-time characteristic. So, the author studies of the ORM technology and Pooled Resources technology.ORM is to resolve the mismatch of the relational database and the object-oriented technology. In short, ORM is a description of the object by using the mapping between databases and metadata, the objects in the process will automatically be saved to the relational databases. In essence it is to convert data from one form to another form. The NCCS Database Middleware applies the C/S structure, including client and server-side. It applies several key technologies, such as the objects dynamic creation, the XML technique, the completion-port model, the realization of object relations theory, the code automatic generation, and so on. The NCCS Database Middleware packs the most of the technical details in database persistence layer, such as transaction management, database connection management, SQL generation, and so on. In this case it liberates the programmers from the ADO code, so that they can put energy and creativity into the real valuable work. And also by the realization of the Object-relational Mapping theory, programmers can apply object-oriented approach to the design of database applications and the system design is provided a more natural way to achieve.The realization of the ORM Persistence Framework implies the additional process spending. However, the NCCS Database Middleware is a middleware, that there will be a lot to do optimization. NCCS Database Middleware applies the Pooled Resources technique such as the Thread Pool and the Connection Pool to improve system performance. Experiments show that: the Thread Pool reduces the overhead of threads during the visiting of numeric customers well, and the Connection Pool technique reduces the spending time to open and close connections during the database access. Finally the two techniques significantly enhance the performance of the system.