Thẻ này cũng quy định rằng ngôn ngữ sẽ được sử dụng trong các scriptlets Java. Bên trong scriptlet đầu tiên, chứa trong các yếu tố kịch bản, tôi thực hiện những hành động tiêu chuẩn tải trình điều khiển, mở một kết nối cơ sở dữ liệu, tạo ra một tuyên bố, | Chapter 19 Accessing Data with Enterprise JavaBeans by Johennie Helton In This Chapter Working with EJBs Introducing EJB classes and interfaces Understanding the EJB lifecycle Using the persistence options available for EJBs Exploring the benefits of data access and value objects Understanding transactions and the transaction attributes in EJBs Guidelines for working with EJBs J2EE Enterprise JavaBeans EJBs are components that provide a model for developing server-side enterprise applications. They encapsulate a part of the application s business logic and make building portable and distributed enterprise applications easier than it would otherwise be. EJBs are intended to provide a data-access platform for your enterprise application. I start with an introduction of the EJB tier and EJB in general and then show you with the aid of examples the different EJB types and their parts as well as the different options regarding data persistence. Finally I provide a set of guidelines that can help you avoid some common mistakes that developers make. Working with the EJB Tier As part of the J2EE standard architecture the Enterprise JavaBean tier provides the environment for the development deployment and life-cycle management of enterprise beans. It is in this tier that you find application-specific business objects and system services such as security and transaction management . Enterprise beans are components of enterprise applications that encapsulate a part of the business logic and typically communicate with resource managers such as database systems application clients servlets and other client types also access the enterprise bean. An application may include one or more entity beans deployed on EJB containers. When the application includes multiple enterprise beans deployment may occur either in a single container or in multiple containers located on the enterprise s network. It is this ability to deploy multiple entity beans on an enterprise s network that form .
