N层与N层架构/设计

Question

N层和N层架构/设计是什么意思？

N层和N层架构/设计之间有什么区别吗？

若有，分别在哪里？

Answer 1

人们经常交替使用这两个术语，因为他们可以将体系结构描述为多层和多层。我的理解是，一般来说，层指的是某种物理分离，而层更多的是逻辑分离。

例如，我想说一个典型的web应用程序有一个前端-浏览器中显示的内容-以及在应用程序服务器上运行的实际应用程序逻辑，以及一个数据库。这可以被称为3层，因为有一个数据库服务器，一个应用服务器和客户机。然而，同样容易的是，可以引用数据库层、逻辑层和表示(或UI)层。

Answer 2

N层指的是系统的“分布式”层(即服务器和客户端)，而n层指的是自包含程序中的层；虽然这两个层经常可以互换使用，但有些人认为有一个显著的差异(就像我上面提到的那个)，就像维基百科上关于Multitier architecture和Multilayered architecture的第一段所看到的那样，解释了这种差异。

Answer 3

此SCEA Study Notes解释了分层体系结构和分层体系结构之间的JEE差异。

Java EE系统的层

* Client (GUI and Web): GUI directly interacts with web tier. Web uses browser, applets to interact with web server through HTTP. Responsible for direct presentation and interaction with user.
* Web components: processes web requests. Acts as mediator between clients and business components.
* Business: (solves domain-specific) business problems. The abstract business logic processing happens in this tier.
* Integration and Resource: handles connectivity with data stores and other (legacy) systems. 

Java EE系统的层

* Virtual platform (component APIs): used to implement/support business logic. API Components include: JavaBeans, Java Servlets, JavaServer Pages/Faces, Java Message Service API, Java Transaction API, etc.
* Application infrastructure (container): responsible for executing the application. Also provides services like: security, transactions, JNDI, and other connectivities.
* Enterprise services (OS): responsible for the execution environment of the application infrastructure. Provides computing time and access to (abstract) hardware.
* Compute and storage: the hardware or physical server. Provides computing power for the OS.
* Networking infrastructure: responsible for networking services.