说明：  J2EE系统架构和设计。本文阐述了J2EE 平台的所有主要技术，围绕J2EE 规范所定义的四个层次： 客户端层（Client Tier）、Web 层(Web Tier)、业务层（Business Tier）及企 业信息系统层（Enterprise Information System Tier），介绍J2EE 所定义的丰 富的技术标准及符合这些标准的开发工具和API，这些技术涵盖了组件技术、 Servlets 和JSP、EJB 技术、数据库访问、分布式通信技术（Java RMI、Java IDL、 JNDI、JMS）、安全等；本文试图给出J2EE 平台技术概念理解上的一个较为清晰 的完整的思路，帮助大家掌握各技术间的相互关系和重要的思想。
(J2EE system architecture and design.In this doc, all the major J2EE platform technologies, focusing on J2EE specification defines four layers: client layer (Client Tier), Web tier (Web Tier), the business layer (Business Tier) and enterprise information system tier (Enterprise Information System Tier), describes the rich J2EE defined technical standards and development tools to meet these standards and the API, these technologies cover the component technology, Servlets and JSP, EJB, database access, distributed communication technology (Java RMI, Java IDL , JNDI, JMS), and safety This article attempts to give the concept of J2EE platform technology, a clearer understanding of the integrity of the ideas to help you grasp the relationship between the technology and important ideas.)