Domain Oriented Data Access Layer Application And Research

The goal of this paper is to implement code generation tool for data access layer based on domain model. This tool can be used as the sub-function of data modeling platform called PowerDesigner. In the enterprise-level system, the split of multi-module is propitious to the deployment and upgrade. But, it's in the core of layer which calls database, so its codes will influent the system performance and stability. Traditional data access layer, it needs programmer to write code by hand, but in fact, the key point and most useful of the system is the business layer. How to design the data access layer is important. Its codes can be generated by different customer demands, even the different data source or demands changed, then the risk can be decreased. For customer demands, domain model can be shown directly. This papers does have a large number of research from domain model, according to O/R Mapping, and analyse the code generation rules.First of all, the papers have some research on current enterprise level system, and provide the code generaion process. Then, it analyses core module of data access level, based on domain model. Finally, it provides the performance of experiment.On association without middle table, because of bi-directional and uni-directional association, this papers comes from bi-directional one-to-many association's prototype, and then iteratively finishes other kinds of association of codes. Then, it provides"Three Level Object Tree"algorithm to provent bi-directional association from dead lock. Meanwhile, it provides"Inverse model"algorithm to resolve the inconsistent data.On association with middle table, the prototype addes the middle table generaion on the basic of one-to-many association prototype, and uses"Dual Protention Dead Lock"to provent repeatable operation for middle table.On inheritance, because of three kinds of O/R Mapping, this papers designs inheritance model which can meet all circumstances, following principle of"self duty link"and"Go Upward to Retrieve, Combind Repeat". To provent the consistence between database and domain object, it also adopts to the"Adapter Deletion"algorithm to provent dead lock as well.When searching object, this papers uses searcher to build object expression, and creates the sql language and parameter in core pare of data access layer.In this papers, it simplies the user development process and time. User needn't call database by hand, but pay more attention to the high-level layer, such as business layer. Once database schema is changed, user only re-generates the data access layer easily.