要创建移动应用程序，单页面应用程序，使用AJAX调用并向客户端提供数据，您需要一个API.如何构造和命名这些API和端点的流行架构风格称为 REST(代表性传输状态). HTTP 1.1的设计考虑了REST原则. REST由 Roy Fielding 于2000年在他的论文Fielding Dissertations中介绍.
RESTful URI和方法为我们提供了处理请求所需的几乎所有信息.下表总结了如何使用各种动词以及如何命名URI.我们将在最后创建一个电影API，所以让我们讨论它将如何构建.
的详细信息
| 方法 | URI | 详细信息 | 功能 |
|---|---|---|---|
| GET | /movies | 安全，可缓存 | 获取所有电影及其详细信息的列表 |
| GET | /movies/1234 | 安全，可缓存 | 获取Movie id 1234 |
| POST | /movies | N/A | 创建一个提供详细信息的新电影. Response包含这个新创建的资源的URI. |
| PUT | /movies/1234 | Idempotent | 修改影片ID 1234(如果尚不存在，则创建一个). Response包含这个新创建的资源的URI. |
| DELETE | /movies/1234 | Idempotent | 如果存在，则应删除电影ID 1234.响应应该包含请求的状态. |
| DELETE或PUT | /movies | 无效 | 应无效. DELETE和PUT应该指定他们正在处理的资源. |
现在让我们在Koa中创建这个API.我们将使用JSON作为我们的传输数据格式，因为它易于在JavaScript中使用并具有许多其他好处.将index.js文件替换为以下 :
INDEX.JS
var koa = require('koa');var router = require('koa-router');var bodyParser = require('koa-body');var app = koa();//Set up body parsing middlewareapp.use(bodyParser({ formidable:{uploadDir: './uploads'}, multipart: true, urlencoded: true}));//Require the Router we defined in movies.jsvar movies = require('./movies.js');//Use the Router on the sub route /moviesapp.use(movies.routes());app.listen(3000);现在我们已经设置了应用程序，让我们专注于创建API.首先设置movies.js文件.我们没有使用数据库来存储电影，而是将它们存储在内存中，因此每次服务器重新启动时，我们添加的电影都将消失.这可以使用数据库或文件(使用节点fs模块)轻松模仿.
导入koa-router，创建路由器并使用module.exports导出它.
var Router = require('koa-router');var router = Router({ prefix: '/movies'}); //Prefixed all routes with /moviesvar movies = [ {id: 101, name: "Fight Club", year: 1999, rating: 8.1}, {id: 102, name: "Inception", year: 2010, rating: 8.7}, {id: 103, name: "The Dark Knight", year: 2008, rating: 9}, {id: 104, name: "12 Angry Men", year: 1957, rating: 8.9}];//Routes will go heremodule.exports = router;GET Routes
定义获取所有电影的GET路线.
router.get('/', sendMovies);function *sendMovies(next){ this.body = movies; yield next;}就是这样.要测试这是否正常，请运行您的应用，然后打开您的终端并输入 :
curl -i -H "Accept: application/json" -H "Content-Type: application/json" -X GET localhost:3000/movies
你会得到以下回复 :
[{"id":101,"name":"Fight Club","year":1999,"rating":8.1},{"id":102,"name":"Inception","year":2010,"rating":8.7},{"id":103,"name":"The Dark Knight","year":2008,"rating":9},{"id":104,"name":"12 Angry Men","year":1957,"rating":8.9}]我们有一条获得所有电影的路线.现在让我们创建一个通过其id获取特定电影的路线.
router.get('/:id([0-9]{3,})', sendMovieWithId);function *sendMovieWithId(next){ var ctx = this; var currMovie = movies.filter(function(movie){ if(movie.id == ctx.params.id){ return true; } }); if(currMovie.length == 1){ this.body = currMovie[0]; } else { this.response.status = 404;//Set status to 404 as movie was not found this.body = {message: "Not Found"}; } yield next;}这将根据我们提供的ID为我们提供电影.要对此进行测试，请在终端中使用以下命令.
curl -i -H "Accept: application/json" -H "Content-Type: application/json" -X GET localhost:3000/movies/101
您将获得响应为 :
{"id":101,"name":"Fight Club","year":1999,"rating":8.1}如果您访问无效路由，它将产生一个无法GET错误，而如果您访问一个ID不存在的有效路由，则会产生404错误.
我们完成了GET路线.现在，让我们转到POST路由.
POST路由
使用以下路由处理POSTed数据.
router.post('/', addNewMovie);function *addNewMovie(next){ //Check if all fields are provided and are valid: if(!this.request.body.name || !this.request.body.year.toString().match(/^[0-9]{4}$/g) || !this.request.body.rating.toString().match(/^[0-9]\.[0-9]$/g)){ this.response.status = 400; this.body = {message: "Bad Request"}; } else { var newId = movies[movies.length-1].id+1; movies.push({ id: newId, name: this.request.body.name, year: this.request.body.year, rating: this.request.body.rating }); this.body = {message: "New movie created.", location: "/movies/" + newId}; } yield next;}这将创建一部新电影并将其存储在电影变量中.要测试此路线，请在您的终端输入以下内容 :
curl -X POST --data "name = Toy%20story&year = 1995&rating = 8.5" https://localhost:3000/movies
您将得到以下回复 :
{"message":"New movie created.","location":"/movies/105"}要测试是否已将其添加到movies对象，请再次运行/movies/105的get请求.您将收到以下回复 :
{"id":105,"name":"Toy story","year":"1995","rating":"8.5"}让我们继续创建PUT和DELETE路线.
PUT路由
PUT路由几乎与POST路由完全相同.我们将指定要更新/创建的对象的id.以下列方式创建路线 :
router.put('/:id', updateMovieWithId);function *updateMovieWithId(next){ //Check if all fields are provided and are valid: if(!this.request.body.name || !this.request.body.year.toString().match(/^[0-9]{4}$/g) || !this.request.body.rating.toString().match(/^[0-9]\.[0-9]$/g) || !this.params.id.toString().match(/^[0-9]{3,}$/g)){ this.response.status = 400; this.body = {message: "Bad Request"}; } else { //Gets us the index of movie with given id. var updateIndex = movies.map(function(movie){ return movie.id; }).indexOf(parseInt(this.params.id)); if(updateIndex === -1){ //Movie not found, create new movies.push({ id: this.params.id, name: this.request.body.name, year: this.request.body.year, rating: this.request.body.rating }); this.body = {message: "New movie created.", location: "/movies/" + this.params.id}; } else { //Update existing movie movies[updateIndex] = { id: this.params.id, name: this.request.body.name, year: this.request.body.year, rating: this.request.body.rating }; this.body = {message: "Movie id " + this.params.id + " updated.", location: "/movies/" + this.params.id}; } }}此路由将执行我们在上表中指定的功能.如果对象存在，它将使用新的详细信息更新对象.如果它不存在，它将创建一个新对象.要测试此路由，请使用以下curl命令.这将更新现有的电影.要创建新电影，只需将ID更改为不存在的ID.
curl -X PUT --data "name = Toy%20story&year = 1995&rating = 8.5" https://localhost:3000/movies/101
Response
{"message":"Movie id 101 updated.","location":"/movies/101"}删除路由
使用以下代码创建删除路由.
router.delete('/:id', deleteMovieWithId);function *deleteMovieWithId(next){ var removeIndex = movies.map(function(movie){ return movie.id; }).indexOf(this.params.id); //Gets us the index of movie with given id. if(removeIndex === -1){ this.body = {message: "Not found"}; } else { movies.splice(removeIndex, 1); this.body = {message: "Movie id " + this.params.id + " removed."}; }}以与我们对其他人相同的方式测试路线.成功删除后(例如id 105)，您将获得 : 去;
{message: "Movie id 105 removed."}最后，我们的movies.js文件看起来像 :
var Router = require('koa-router');var router = Router({ prefix: '/movies'}); //Prefixed all routes with /moviesvar movies = [ {id: 101, name: "Fight Club", year: 1999, rating: 8.1}, {id: 102, name: "Inception", year: 2010, rating: 8.7}, {id: 103, name: "The Dark Knight", year: 2008, rating: 9}, {id: 104, name: "12 Angry Men", year: 1957, rating: 8.9}];//Routes will go hererouter.get('/', sendMovies);router.get('/:id([0-9]{3,})', sendMovieWithId);router.post('/', addNewMovie);router.put('/:id', updateMovieWithId);router.delete('/:id', deleteMovieWithId);function *deleteMovieWithId(next){ var removeIndex = movies.map(function(movie){ return movie.id; }).indexOf(this.params.id); //Gets us the index of movie with given id. if(removeIndex === -1){ this.body = {message: "Not found"}; } else { movies.splice(removeIndex, 1); this.body = {message: "Movie id " + this.params.id + " removed."}; }}function *updateMovieWithId(next) { //Check if all fields are provided and are valid: if(!this.request.body.name || !this.request.body.year.toString().match(/^[0-9]{4}$/g) || !this.request.body.rating.toString().match(/^[0-9]\.[0-9]$/g) || !this.params.id.toString().match(/^[0-9]{3,}$/g)){ this.response.status = 400; this.body = {message: "Bad Request"}; } else { //Gets us the index of movie with given id. var updateIndex = movies.map(function(movie){ return movie.id; }).indexOf(parseInt(this.params.id)); if(updateIndex === -1){ //Movie not found, create new movies.push({ id: this.params.id, name: this.request.body.name, year: this.request.body.year, rating: this.request.body.rating }); this.body = {message: "New movie created.", location: "/movies/" + this.params.id}; } else { //Update existing movie movies[updateIndex] = { id: this.params.id, name: this.request.body.name, year: this.request.body.year, rating: this.request.body.rating }; this.body = {message: "Movie id " + this.params.id + " updated.", location: "/movies/" + this.params.id}; } }}function *addNewMovie(next){ //Check if all fields are provided and are valid: if(!this.request.body.name || !this.request.body.year.toString().match(/^[0-9]{4}$/g) || !this.request.body.rating.toString().match(/^[0-9]\.[0-9]$/g)){ this.response.status = 400; this.body = {message: "Bad Request"}; } else { var newId = movies[movies.length-1].id+1; movies.push({ id: newId, name: this.request.body.name, year: this.request.body.year, rating: this.request.body.rating }); this.body = {message: "New movie created.", location: "/movies/" + newId}; } yield next;}function *sendMovies(next){ this.body = movies; yield next;}function *sendMovieWithId(next){ var ctx = this var currMovie = movies.filter(function(movie){ if(movie.id == ctx.params.id){ return true; } }); if(currMovie.length == 1){ this.body = currMovie[0]; } else { this.response.status = 404;//Set status to 404 as movie was not found this.body = {message: "Not Found"}; } yield next;}module.exports = router;这样就完成了我们的REST API.现在，您可以使用这种简单的架构风格和Koa创建更复杂的应用程序.