毕业设计外文资料翻译-Node.js 框架比较 Express vs.Koa vs.Hapi

1、毕业设计外文资料翻译学 院： 专业班级： 学生姓名： 学 号： 指导教师： 外文出处：(外文) Node.js Framework Comparison: Express vs. Koa vs. Hapi.2014(1551) 附 件：1.外文资料翻译译文； 2.外文原文 指导教师评语：原文所涉及内容与课题有较好的关联，翻译难度适中。该生所作的译文，术语的使用基本准确，译文内容与原文含义基本相符，但部分译文语句不是很通顺。译文格式符合规范，按时完成了下达的外文翻译任务。签名： 年 月 日1外文资料翻译译文Node.js 框架比较: Express vs.Koa vs.Hapi1 介绍Expre

2、ss.js无疑是当前Node.js中最流行的Web应用程序框架。它几乎成为了大多数Node.js web应用程序的基本的依赖，甚至一些例如Sails.js这样的流行的框架也是基于Express.js。然而你还有一些其他框架的选择，可以给你带来“sinatra”一样的感觉（译注：sinatra是一个简单的Ruby的Web框架，可以参考 HYPERLINK /2014/11/27/sinatra-introduction/ t _blank 这篇博文）。另外两个最流行的框架分别是Koa和Hapi。这篇文章不是打算说服你哪个框架比另外一个更好，而是只是打算让你更好地理解每个框架能做什么，什么情况下一

3、个框架可以秒杀另外一个。2 框架的背景我们将要探讨的两个框架看起来都非常相似。每一个都能够用几行代码来构建一个服务器，并都可以非常轻易地构建REST API。我们先瞧瞧这几个框架是怎么诞生的。2.1 Express2009年6月26日，TJ Holowaychuk提交了Express的第一次commit，接下来在2010年1月2日，有660次commits的Express 0.0.1版本正式发布。TJ和Ciaron Jessup是当时最主要的两个代码贡献者。在第一个版本发布的时候，根据github上的readme.md，这个框架被描述成：疯一般快速（而简洁）的服务端JavaScript Web

4、开发框架，基于Node.js和V8 JavaScript引擎。差不多5年的时间过去了，Express拥有了4,925次commit，现在Express的最新版本是4.10.1，由StrongLoop维护，因为TJ现在已经跑去玩Go了。2.2 Koa大概在差不多一年前的2013年8月17日，TJ Holowaychuk（又是他！）只身一人提交了Koa的第一次commit。他描述Koa为“表现力强劲的Node.js中间件，通过 HYPERLINK /tj/co t _blank co使用generators使得编写web应用程序和REST API更加丝般顺滑”。Koa被标榜为只占用约400行源码空

5、间的框架。Koa的目前最新版本为0.13.0，拥有583次commits。2.3 Hapi2011年8月5日，WalmartLabs的一位成员Eran Hammer提交了Hapi的第一次commit。Hapi原本是Postmile的一部分，并且最开始是基于Express构建的。后来它发展成自己自己的框架，正如Eran在他的博客里面所说的：Hapi基于这么一个想法：配置优于编码，业务逻辑必须和传输层进行分离. Hapi最新版本为7.2.0，拥有3,816次commits，并且仍然由Eran Hammer维护。所有开发者要开发Node.js web应用程序的第一步就是构建一个基本的服务器。所以我们

6、来看看用这几个框架构建一个服务器的时候有什么异同。3 创建一个服务器所有开发者要开发Node.js web应用程序的第一步就是构建一个基本的服务器。所以我们来看看用这几个框架构建一个服务器的时候有什么异同。3.1 Express对于所有的node开发者来说，这看起来相当的自然。我们把express require进来，然后初始化一个实例并且赋值给一个为app的变量。接下来这个实例初始化一个server监听特定的端口，3000端口。app.listen()函数实际上包装了node原生的http.createServer()函数。3.2 Koa你马上发现Koa和Express是很相似的。其实差别只

7、是你把require那部分换成koa而不是express而已。app.listen()也是和Express一模一样的对原生代码的封装函数。3.3 HapiHapi是三者中最独特的一个。和其他两者一样，hapi被require进来了但是没有初始化一个hapi app而是构建了一个server并且指定了端口。在Express和Koa中我们得到的是一个回调函数而在hapi中我们得到的是一个新的server对象。一旦我们调用了server.start()我们就开启了端口为3000的服务器，并且返回一个回调函数。这个server.start()函数和Koa、Express不一样，它并不是一个http.C

8、reateServer()的包装函数，它的逻辑是由自己构建的。4路由控制现在一起来搞搞一下服务器最重要的特定之一，路由控制。我们先用每个框架分别构建一个老掉渣的“Hello world”应用程序，然后我们再探索一下一些更有用的东西，REST API。4.1 Hello WorldExpress我们用get()函数来捕获“GET /”请求然后调用一个回调函数，这个回调函数会被传入req和res两个对象。这个例子当中我们只利用了res的res.send()来返回整个页面的字符串。Express有很多内置的方法可以用来进行路由控制。get,post,put,head,delete等等这些方法都是Ex

9、press支持的最常用的方法（这只是一部分而已，并不是全部）。Koa和Express稍微有点儿不同，它用了ES6的generators。所有带有*前缀的函数都表示这个函数会返回一个generator对象。根本上来说，generator会同步地yield出数据（译注：如果对Python比较熟悉的话，应该对ES6的generator不陌生，这里的yield其实和Python的yield语句差不多一个意思），这个超出本文所探索的内容，不详述。在app.use()函数中，generator函数设置响应体。在Koa中，this这个上下文其实就是对node的request和response对象的封装。th

10、is.body是KoaResponse对象的一个属性。this.body可以设置为字符串, buffer, stream, 对象, 或者null也行。上面的例子中我们使用了Koa为数不多的中间件的其中一个。这个中间件捕获了所有的路由并且响应同一个字符串。Hapi这里使用了server对象给我们提供的server.route内置的方法，这个方法接受配置参数：path（必须），method（必须），vhost，和handler（必须）。HTTP方法可以处理典型的例如GET、PUT、POST、DELETE的请求，*通配符可以匹配所有的路由。handler函数被传入一个request对象的引用，它必须

11、调用reply函数包含需要返回的数据。数据可以是字符串、buffer、可序列化对象、或者stream。.4.2 REST APIHello world除了给我们展示了如何让一个应用程序运行起来以外几乎啥都没干。在所有的重数据的应用程序当中，REST API几乎是一个必须的设计，并且能让我们更好地理解这些框架是可以如何使用的。现在让我们看看这些框架是怎么处理REST API的。Express我们为已有的Hello World应用程序添加REST API。Express提供一些处理路由的便捷的方式。这是Express 4.x的语法，除了你不需要express.Router()和不能用app.use

12、r(/api, router)以外，其实上是和Express 3.x本质上是一样的。在Express 3.x中，你需要用app.route()替换router.route()并且需要加上/api前缀。Express 4.x的这种语法可以减少开发者编码错误并且你只需要修改少量代码就可以修改HTTP方法规则。Koa很明显，Koa并没有类似Express这样的可以减少编码重复路由规则的能力。它需要额外的中间件来处理路由控制。我选择使用koa-route因为它是由Koa团队维护的，但是还有很多由其他开发者维护的可用的中间件。Koa的路由和Express一样使用类似的关键词来定义它们的方法，.get()

13、,.put(),.post(), 和.delete()。Koa在处理路由的时候有一个好处就是，它使用ES6的generators函数来减少对回调函数的处理。Hapi对于Hapi路由处理的第一印象就是，相对于其它两个框架，这货是多么的清爽，可读性是多么的棒！即使是那些必须的method，path，handler和reply配置参数都是那么的赏心悦目（译注：作者高潮了）。类似于Koa，Hapi很多重复的代码会导致更大的出错多可能性。然而这是Hapi的有意之为，Hapi更关注配置并且希望使得代码更加清晰和让团队开发使用起来更加简便。Hapi希望可以不需要开发者进行编码的情况下对错误处理进行优化。如果

14、你尝试去访问一个没有被定义的REST API，它会返回一个包含状态码和错误的描述的JSON对象。.5 优缺点比较5.1 Express优点Express拥有的社区不仅仅是上面三者当中最大的，并且是所有Node.js web应用程序框架当中最大的。在经过其背后差不多5年的发展和在StrongLoop的掌管下，它是三者当中最成熟的框架。它为服务器启动和运行提供了简单的方式，并且通过内置的路由提高了代码的复用性。缺点使用Express需要手动处理很多单调乏味的任务。它没有内置的错误处理。当你需要解决某个特定的问题的时候，你会容易迷失在众多可以添加的中间件中，在Express中，你有太多方式去解决同一

15、个问题。Express自诩为高度可配置，这有好处也有坏处，对于准备使用Express的刚入门的开发者来说，这不是一件好的事情。并且对比起其他框架来说，Express体积更大。5.2 Koa优点Koa有着傲人的身材（体积小），它表现力更强；对比起其他框架，它使得中间件的编写变的更加容易。Koa基本上就是一个只有骨架的框架，你可以选择（或者自己写一个）中间件，而不用妥协于Express或者Hapi它们自带的中间件。它也是唯一一个采用ES6的框架，例如它使用了ES6的generators。缺点Koa不稳定，仍处于活跃的开发完善阶段。使用ES6还是有点太超前了，例如只有0.11.9+的Node.js版

16、本才能运行Koa，而现在最新的Node.js稳定版本是0.10.33。和Express一样有好也有坏的一点就是，在多种中间件的选择还是自己写中间件。就像我们之前所用的router那样，有太多类似的router中间件可供我们选择。5.3 Hapi优点Hapi自豪地宣称它自己是基于配置优于编码的概念，并且很多开发者认为这是一件好事。在团队项目开发中，可以很容易地增强一致性和可复用性。作为有着大名鼎鼎的WalmartLabs支持的框架和其他响当当的企业在实际生产中使用Hapi，它已经经过了实际战场的洗礼，企业们可以没有担忧地基于Hopi运行自己的应用程序。所有的迹象都表明Hapi向着成为的伟大的框架

17、的方向持续成熟。缺点Hapi绝逼适合用来开发更大更复杂的应用。但对于一个简单的web app来说，它的可能有点儿堆砌太多样板代码了。而且Hapi的可供参考样例太少了，或者说开源的使用Hapi的应用程序太少了。所以选择它对开发者的要求更高一点，而不是所使用的中间件。6 总结我们已经看过三个框架一些棒棒的而且很实际的例子了。Express毫无疑问是三个当中最流行和最出名的框架。当你要开发一个新的应用程序的时候，使用Express来构建一个服务器可能已经成为了你的条件反射了；但希望现在你在做选择的时候会多一些思考，可以考虑选择Koa或者Hapi。Koa通过超前拥抱ES6和Web component的

18、思想，显示了Web开发社区正在进步的对未来的承诺。对于比较大的团队和比较大的项目来说，Hapi应该成为首要选择。它所推崇的配置优于编码，对团队和对团队一直追求的可复用性都大有裨益。现在赶紧行动起来尝试使用一个新的框架，可能你会喜欢或者讨厌它，但没到最后你总不会知道结果是怎么样的，有一点无容置疑的是，它会让你成为一个更好的开发者。2.外文原文Node.js Framework Comparison: Express vs. Koa vs. Hapi1 IntroductionExpress.js is the most popular Node.js web application framew

19、ork used today. It seems to be the base dependency in most Node.js web applications, even some popular frameworks like Sails.js are built off of Express. However there are more options available that have the same sinatra-like feel to them. The next two most popular frameworks are Koa and Hapi respe

20、ctively.This is not going to persuade you to use one framework over the other, its merely going to help you get a better understanding of what each framework can do and where one might trump the other.2 Framework backgroundsAll three of the frameworks we will be looking at have a lot in common. All

21、can create a server with just a few lines of code and all make creating a REST API very simple. Lets look at how these frameworks began.2.1 ExpressThe initial commit for Express was made on June 26, 2009 by TJ Holowaychuk and 660 commits later version 0.0.1 was released on January 2, 2010. The two m

22、ain contributors at that time were TJ and Ciaron Jessup. At the time of the first release the framework was described as per the readme.md on githubInsanely fast (and small) server-side JavaScript web development framework built onnode.jsandV8 JavaScript engine. Fast forward almost 5 years and 4,925

23、 commits, now 4.10.1 is the latest version maintained by StrongLoop as TJ is now concentrating in the Go-Lang community.2.2 KoaThe initial commit for Koa was just over a year ago on August 17, 2013 by none other than TJ Holowaychuk. He describes it as Expressive middleware for node.js using generato

24、rs via HYPERLINK /visionmedia/co coto make writing web applications and REST APIs more enjoyable to write. Koa is advertised as having a small footprint of 400 SLOC. It is now on version 0.13.0 with 585 commits.2.3 HapiThe initial commit for Hapi was on August 5, 2011 by Eran Hammer a member of Walm

25、artLabs. Hapi was created by parts of HYPERLINK /hueniverse/postmile Postmileand was originally built on top of Express. Later it was developed into its own framework because of what Erin states in his blog: hapi was created around the idea thatconfiguration is better than code, thatbusiness logic m

26、ust be isolated from the transport layer. 3,816 commits later Hapi is is on version 7.2.0 and is still maintained by Eran Hammer.3 Creating a serverThe first step for any developer when working on a Node.js web application is to create a basic server. So lets create a server using each framework to

27、see their similarities and differences.3.1 ExpressThis is probably pretty natural to all node developers. We require express and then instantiate it by assigning it to the variableapp. Then instantiate a server to listen to a port, port 3000. Theapp.listen()is actually just a wrapper around nodeshtt

28、p.createServer().3.2 KoaRight away you can see that Koa is similar to Express. Essentally you just required koa instead of express. Alsoapp.listen()is the exact same wrapper function as used in Express.3.3 HapiHapi is the unique one of the group. First like always, hapi is required but instead of in

29、stantiating a hapiapp, you create a new Server and specify the port. In Express and Koa we get a callback function but in Hapi we get a newserverobject. Then once we callserver.start()we start the server on port 3000 which then returns a callback. However this is not like Koa and Express, it is not

30、a wrapper aroundhttp.CreateServer(), it is using its own logic.4 RoutesNow lets dig into one of the most important features of a server, routing. First lets create the cliche Hello world application for each framework and then move on to something a little more useful, REST API.4.1 Hello World Expre

31、ss We are using theget()method to catch the incoming request of GET / and then invoke a callback function that handles two parametersreqandres. For this example we are only utilizingresto return back to the page a string usingres.send(). Express has a variety of built in methods that are used to han

32、dle the routing functionality. The following are some of the more commonly used methods that are supported by Express (but not all of the methods):get,post,put,head,delete.Koa is slightly different than Express, it is using ES6 generators. Any function preceded by a*means the function will return a

33、generator object. Basically these generatorsyieldvalues synchronously but that is beyond the scope of this post. Within theapp.use()the generator functionsetstheresponsebody.InKoatheContextwhichisequivalenttothethisidentifierisanencapsulationofnodesrequestandresponseobjects.this.bodyisamethodintheKo

34、aResponseobject.this.bodycan be set to a string, buffer, stream, object, or null. This example we used one of the few middlewares provided in the Koa core. This middleware we used catches all routes and responds with the string provided.Hapi Here we are using the built in method that theserverobject

35、 provides usserver.route()whichhasthefollowingoptions:path(required),method(required),vhost,andhandler(required).TheHTTPmethodcanhandlethetypical requestsGET,PUT,POST,DELETE, and*which catches any route. The handler is passed a reference to therequestobject and must callreplywith the containing payl

36、oad. The payload can be a string, a buffer, a serializable object, or a stream.4.2 REST APIThe Hello world never really does much except show the most basic/simplest way to get an application up and running. REST APIs are almost a must in all data heavy applications and will help better understand h

37、ow these frameworks can be used. So lets take a look at how each handles REST APIs.Express So we added our REST API to our existing Hello World application. Express offers a little shorthand for handling routes. This is Express 4.x syntax but it is essentially the same in Express 3.x except you dont

38、 need theexpress.Router()and you will not be able to use the lineapp.use(/api, router). Instead you will replace therouter.route()s withapp.route()while prepending the existing verb with/api. This is a nice approach because it reduces the chance of developer errors and minimizes the places to change

39、 the HTTP method verbs.Koa Its pretty obvious that Koa doesnt have the ability to reduce the repetitive route verbs like Express. It also requires a separate middleware to handle routes. I chose to usekoa-routebecause it is maintained by the Koa team but there are a lot of routes available to use by

40、 other maintainers. The routes are very similar to Express with using the same keywords for their method calls like.get(),.put(),.post(), and.delete(). One advantage Koa has with handling its routes, is that it is using the ES6 generator functions which helps reduce the handling of callbacks.Hap iFi

41、rst impressions of the routes in Hapi are how clean and readable they are compaired to the other frameworks. Even the required optionsmethod,path,handler, andreplayfor the routes are easy to the eye. Like Koa, there is a lot of reuse of code making the room for error larger. However this is intentio

42、n, Hapi is more concerned about configuration and wants the code to be cleaner for easier use in a team. Hapi also wanted to improve error handling which it does without any code being written on the developers end. If you try to hit a route not described in the REST API it will return a JSON object

43、 with a status code and error description.5 The Good and The Bad5.1 ExpressThe GoodExpress has the biggest community not only out of the three frameworks compared here but out of all the web application frameworks for Node.js. It is the most matured framework out of the three, with almost 5 years of

44、 development behind it and now has StrongLoop taking control of the repository. It offers a simple way to get a server up and running and promotes code reuse with its built in router.The BadThere is a lot of manual tedious tasks involved in Express. There is no built in error handling, it is easy to

45、 get lost in all of the middleware that could be added to solve a solution, and there are many ways to do one thing. Express describes itself as being opinionated, this could be good or bad but for beginning developers who must likely chose Express, this is a bad thing. Express also has a larger foo

46、t print compared to the other frameworks.5.2 KoaThe GoodKoa has a small footprint, it is more expressive and it makes writing middleware a lot easier than the other frameworks. Koa is basically a barebone framework where the developer can pick (or write) the middleware they want to use rather than c

47、ompromising to the middleware that comes with Express or Hapi. Its the only framework embracing ES6, for instance its using ES6 generators.The BadKoa is still unstable and heavily in development. Using ES6 is still ahead of the game for example version 0.11.9+ of Node.js needs to be used to run Koa

48、and right now the latest stable version on Node.js is version 0.10.33. One thing that is in the good but could also be in the bad much like Express is the option of selecting multiple middlewares or writing your own middleware. Such as the router we looked at earlier, there are a lot of middleware routers to handle a variety of options.5.3 HapiThe GoodHapi is proud to say that their framework is based on configuration over code, and a lot of developers would argue that this is a good thing. This