EJB基礎(chǔ)與會話Bean[外文翻譯]

包括中文翻譯和英文原文

EJB基礎(chǔ)與會話Bean

到目前為止，我們已經(jīng)討論了用戶界面，業(yè)務(wù)邏輯和開發(fā)Java EE應(yīng)用程序的數(shù)據(jù)庫連接方面的問題。討論的主要機制是為指出從JSP和Servlet代碼被訪問的JavaBeans所表達(dá)業(yè)務(wù)邏輯。Java EE有一個表達(dá)了一個應(yīng)用程序的業(yè)務(wù)邏輯和數(shù)據(jù)庫訪問使用一個JavaBeans一樣強大的概念專用設(shè)施。該設(shè)施是企業(yè)JavaBeans，EJB的已很少被認(rèn)知。
在這一章中，我們將開始探討EJB，這是一個對Java EE平臺很重要的能力世界。 EJB的開發(fā)和部署提供關(guān)鍵任務(wù)企業(yè)應(yīng)用的基礎(chǔ)設(shè)施。我們首先看一些EJB的基礎(chǔ)，然后集中在一個類型的EJB：會話bean。
在這一章中，你將學(xué)習(xí)以下內(nèi)容：
•使用EJB的好處
•EJB的三種好處：會話，實體和消息驅(qū)動beans
•會話beans的組成
•如何開發(fā)會話beans
•有狀態(tài)和無狀態(tài)會話beans的區(qū)別

EJB Fundamentals and Session Beans
So far, we’ve discussed the user interface, business logic, and database connection aspects of developing Java EE applications. The primary mechanism discussed to this point for expressing business logic has been JavaBeans accessed from JSP and Servlet code. Java EE has a powerful facility dedicated to expressing the business logic of an application and for accessing a database using a JavaBeans-like concept. That facility is Enterprise JavaBeans, known as EJBs for short.
In this chapter, we’ll begin exploring the world of EJBs, which is a very important capability of the Java EE platform. EJBs provide infrastructure for developing and deploying mission-critical,enterprise applications. We’ll first look at some EJB fundamentals, and then focus on one type of EJB: the session bean.
In this chapter, you will learn the following:
• The benefits of using EJBs
• The three kinds of EJBs: session, entity, and message-driven beans
• The makeup of session beans
• How to develop session beans
• Differences between stateful and stateless session beans