| This article mainly discusses the research and development of data access layer in management and control system of thermal power plants. Methods for designing light-weight ORM architecture and DAO architecture are put forward in this article.It presents background of the engineering project, meaning of research, related theory of data access technology on J2EE. With the analysis of thermal power plants'management and control system, paradigm non-matching problem between object model and relational model emerges in the field of business entity.To resolve the paradigm non-matching problem and decouple data access logic form business logic, several core components of light-weight ORM architecture are brought forward.Through these components'integration,a universal and light data access layer which can be used as a plug-in of J2EE application is developed.Using XML as metadata to configure system,the JDBC SQL statements embedded in Java programs separate from business logic codes.The article aims to design a light-weight ORM mechanism and implement the object-persistence solution based on J2EE. Data access layer decoupled from the origin system provides transaction control on data access to ensure data consistency and access security. Also, it utilizes technologies such as lazy-loading and object cache to improve the performance of data access layer.To decouple data access much more, DAO pattern is introduced into ORM architecture.DAO divides data access logic into abstract layer and implemented layer.It separates data use from details about data access, so system can extend flexibly.Combined with DTO pattern, DAO architecture encapsulates data access objects and hides concrete implementation of object persistence from business logic layer.The light-weight data access layer composed of ORM mechanism and DAO architecture is deployed in practical enterprise business applications.It exerts a profound function as data access middleware and reinforces the origin system. |
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