RESTful API（RESTful APIs）

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(Representational Transfer State) 。 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谓词以及如何命名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。

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，因为它易于使用JavaScript并具有许多其他好处。 用以下内容替换index.js文件 -

INDEX.JS

var koa = require('koa');
var router = require('koa-router');
var bodyParser = require('koa-body');
var app = koa();
//Set up body parsing middleware
app.use(bodyParser({
   formidable:{uploadDir: './uploads'},
   multipart: true,
   urlencoded: true
}));
//Require the Router we defined in movies.js
var movies = require('./movies.js');
//Use the Router on the sub route /movies
app.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 /movies
var 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 here
module.exports = router;

GET路线

定义获取所有电影的GET路线。

router.get('/', sendMovies);
function *sendMovies(next){
   this.body = movies;
   yield next;
}

而已。 要测试这是否正常，运行您的应用程序，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

你会得到以下回应 -

[{"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

你会收到回复 -

{"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，它将产生404错误。

我们完成了GET路线。 现在，让我们继续进行POST路由。

POST路线

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;
}

这将创建一个新电影并将其存储在电影变量中。 要测试此路线，请在终端中输入以下内容 -

curl -X POST --data "name = Toy%20story&year = 1995&rating = 8.5" 
https://localhost:3000/movies

你会得到以下回应 -

{"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。 你会得到以下回应 -

{"id":105,"name":"Toy story","year":"1995","rating":"8.5"}

让我们继续创建PUT和DELETE路由。

PUT路线

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};
      }
   }
}

该路由将执行我们在上表中指定的功能。 它将使用新的详细信息更新对象（如果存在）。 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

响应 (Response)

{"message":"Movie id 101 updated.","location":"/movies/101"}

删除路线

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."};
   }
}

以与我们为其他人相同的方式测试路线。 删除成功后（例如id 105），您将获得 -

{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 /movies
var 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 here
router.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。