Entity Bean Container And Container-managed Persistence

The Enterprise JavaBeans architecture is a component architecture for the development and deployment of component-based distributed business applications. Applications written using the Enterprise JavaBeans architecture are scalable, transactional, and multi-user secure. Programmed with pure Java, The EJB component is independent of the platform. For this independence, the EJB is more fittable to develop distributed application than other component-based technology.The entity bean is one type of EJB. Because it can persist its state, it is often used to represent the business entity. There are many kinds of technology that can be used to persist object, but none of them except the entity bean can be efficiently used to develop a distributed application. One reason is that they don't have a complete specification. But the entity bean has one.The EJB specification defines how to develop an entity bean and what support is necessary for it to run. However, it is not specified how to provide those supports. There are many application servers that implement the functions defined in the sepecification. However, as the entity bean is more and more widely used, the deficiency and inconvenience is more and more clear. A better implementation is expected.This paper represents an implementation of parts of the specification for the entity bean. In the implementation, we try to avoid the known deficiencies. So we adopt the following mechanisms: an object cache, a configurable synchronize policy and a dead-lock-detection algorithem. Besides, we also try to improve the persistent mechanism by adopting the following: selection of the best OR mapping, optimization of the database-access operation. In one word, the implementation is high performance, EJB2.0 compliant and easy to configure.The implementation is a key component of OnceAS, which is a J2EE1.3 compliant application server developed independently by TCSE, ISCAS.