什么是 N 层架构? [英] What is N-Tier architecture?

问题描述

我最近看到不少开发人员职位发布，其中包含或多或少这样的句子:必须具有 N 层架构经验"或必须能够开发 N 层应用程序".

这让我想问，什么是 N 层架构?如何获得经验?

解决方案

类或 Web 服务协议，如 SOAP 是在电线上飞行物体的少数尝试.

I've seen quite a few developer job postings recently that include a sentence that reads more or less like this: "Must have experience with N-Tier architecture", or "Must be able to develop N-Tier apps".

This leads me to ask, what is N-Tier architecture? How does one gain experience with it?

解决方案

Wikipedia:

In software engineering, multi-tier architecture (often referred to as n-tier architecture) is a client-server architecture in which, the presentation, the application processing and the data management are logically separate processes. For example, an application that uses middleware to service data requests between a user and a database employs multi-tier architecture. The most widespread use of "multi-tier architecture" refers to three-tier architecture.

It's debatable what counts as "tiers," but in my opinion it needs to at least cross the process boundary. Or else it's called layers. But, it does not need to be in physically different machines. Although I don't recommend it, you can host logical tier and database on the same box.

Edit: One implication is that presentation tier and the logic tier (sometimes called Business Logic Layer) needs to cross machine boundaries "across the wire" sometimes over unreliable, slow, and/or insecure network. This is very different from simple Desktop application where the data lives on the same machine as files or Web Application where you can hit the database directly.

For n-tier programming, you need to package up the data in some sort of transportable form called "dataset" and fly them over the wire. .NET's DataSet class or Web Services protocol like SOAP are few of such attempts to fly objects over the wire.

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