Based On Distributed Data Access Framework

With the wide use of computer technology, the scale of software becomes bigger and bigger, and datum deal with get more and more complicated. J2EE becomes the main platform of large-scale software development. Its mechanisms of data persistence becomes the data persistence standard of J2EE based development, and have got widely use. Nowadays , multi-database application and migratio database application must be solved, and the improvement of database access layer's design is also necessary , which is becoming into an important research field . Howerver , The large number of kinds and complicated datum need one uniform, high efficient mechanism; the mature data persistence mechanism from J2EE can not balance well between runtime efficiency and developing efficiency, and can not provide a uniform and straight forward management mode.Based on the above, the paper focuses on there search of Data Access Object(DAO) and Object relation Mapping(O/R Mapping), Then this thesis studies the many technologies for implementing O/R mapping in Java environment such as JDBC, Enterprise Entity Bean, JDO ( Java Data Object ) and third party O/R mapping tools. Also this thesis discusses the technologies in detail and brings forward own the framework of distributed data access , design and develop a framework named GDA , which can access most kinds of database .This framework offers an uniform interface for all application softwares, by which you can access most kinds of databases transparently. This thesis analyzes the rationale of O/R mapping focusing on the mapping taken between the Class with its instance and the SQL in RDBMS. TO simplify the use of JDBC and concealing some data access operations inside the target database. It should be possible to change an application's persistence strategy without rewriting its business logic.And also introduce the Aspect-Oriented Programming (AOP). It can reduce difficulty and complexity in developing middleware. Implementing tranactions module of the framework by using AOP. It should ensure correct behavior on concurrent attempts to access and manipulate the same data.This usually means preventing concurrent updates from compromising data integrity, while minimizing the impact of the necessary locking on application throughput. The tasks are:1.Analyze the Data Access framework in detail. 2.Design and develop a framework named GDA. 3 .ImplementSqlMapping,Logs and OID Generator module. 4.Design and implement tranactions module of GDA. 5.Make a testing plan of GDA .Finally, the summary and further research are given in theend of this dissertation.