原文：http://docs.oracle.com/javaee/7/tutorial/doc/overview002.htm
翻译：石卓林 shizhuolin@hotmail.com

1.2 Java EE Application Model

The Java EE application model begins with the Java programming language and the Java virtual machine. The proven portability, security, and developer productivity they provide forms the basis of the application model. Java EE is designed to support applications that implement enterprise services for customers, employees, suppliers, partners, and others who make demands on or contributions to the enterprise. Such applications are inherently complex, potentially accessing data from a variety of sources and distributing applications to a variety of clients.

To better control and manage these applications, the business functions to support these various users are conducted in the middle tier. The middle tier represents an environment that is closely controlled by an enterprise’s information technology department. The middle tier is typically run on dedicated server hardware and has access to the full services of the enterprise.

The Java EE application model defines an architecture for implementing services as multitier applications that deliver the scalability, accessibility, and manageability needed by enterprise-level applications. This model partitions the work needed to implement a multitier service into the following parts:

• The business and presentation logic to be implemented by the developer
• The standard system services provided by the Java EE platform

The developer can rely on the platform to provide solutions for the hard systems-level problems of developing a multitier service.

1.2 Java EE 应用模型

Java EE应用模型使用Java程序语言和Java虚拟机,事实证明以应用模型为基础提供了轻量,安全,和更高的开发效率.Java EE旨支持实现为客户,员工,供应商,合作伙伴或其他人提出的要求服务或对企业需求服务的企业应用.这样的应用本身就很复杂.从多种来源都可能访问数据和应用并且要分发到不同的客户端.

为了更好的控制和管理这些应用, 设计在中间层的业务功能支持各种各样的用户和条件.中间层描述了一个受到企业信息技术部门严格控制的环境.中间层通常是运行在一个专用的服务器硬件上提供全部的服务供企业.

Java EE应用模型定义了一个符合可行性,可扩展性,可访问性和可管理性的需求的企业级多层应用架构.这种模式把多层服务分割为以下几个部分:

• 由开发者实现业务逻辑和表示逻辑
• 由Java EE 平台提供标准系统服务

开发者可以信任平台提供的硬系统级多层服务解决方案