Research And Implementation Of Data Persistence Layer Based On Object Relation Mapping Technology

Nowdays Object-oriented development method has been widely used in the most enterprise-level applications while RDBMS is the predominant storage mechanism to persist data.As object-oriented technology based on object theory and relational database based on set theory,which led to problem of”impedance mismatch”between the object model and the relational model.To solve this problem,ORM(Object-Relational Mapping)technology emerges.This paper throughly studies the ORM technology.In its application,there is a persistence layer framework based on.NET.This paper makes two aspects improvement on the basis of the framework,one is the improvement of the query method of persistent object,the other is the improvement of object prefetch way,and the paper applies the improved framework in the actual system.The major focues of this paper are as follows:1)It explains the concept and the method of data persistence,and analyzes the cause of the “impedance mismatch” problem between the object model and the relational model.Based on this issue introduces the popular ORM technology to solve this problem,and analyzes its theroy.2)It studies deeply NHibernate,which is widely used as ORM framework.This paper focuse on the analysis of NHibernate,and puts forward the disadvantages of NHibernate.Based on the disadvantage,this paper improved the NHibernate,mainly includes the improvement of caching and prefetching technology.In the mode of object query,adopts the way of lazy loading;In the mode of prefetching,applies the incremental prefetching technique based on log.It compares the performance before and after improvement through the experiment,proves the improvement effect of significant.3)In virtue of UML,in.NET platform,using C# language and other developing means,this paper elaborates the design and implementation of Car Modify Information Management System,designs a data persistence model framework based on NHibernate and Three-tier architecture,introduces the persistence layer implementation of the system in detail.It takes inventory management model as example,illustrates how to use the improved NHibernate framework in actual system.The system is running in good condition,fully demonstrated the effectiveness of the improved framework.