[转]nodeJs--koa2 REST API

本文转自：https://blog.csdn.net/davidPan1234/article/details/83413958

REST API规范
编写REST API，实际上就是编写处理HTTP请求的async函数，不过，REST请求和普通的HTTP请求有几个特殊的地方：

REST请求仍然是标准的HTTP请求，但是，除了GET请求外，POST、PUT等请求的body是JSON数据格式，请求的Content-Type为application/json；
REST响应返回的结果是JSON数据格式，因此，响应的Content-Type也是application/json。
1、工程结构

2、目录详解
package.json:项目描叙

{
"name": "rest-koa",
"version": "1.0.0",
"description": "rest-koa project",
"main": "app.js",
"scripts": {
"dev": "node --use_strict app.js"
},
"keywords": [
"koa",
"rest",
"api"
],
"author": "david pan",
"dependencies": {
"koa": "2.0.0",
"koa-bodyparser": "3.2.0",
"koa-router": "7.0.0"
}
}
app.js

const Koa = require('koa');
const app = new Koa();

const bodyParser = require('koa-bodyparser');
const controller = require('./controller');
const rest = require('./rest');

// parse request body:
app.use(bodyParser());
// bind .rest() for ctx:
app.use(rest.restify());
// add controller:
app.use(controller());

app.listen(3000);
console.log('app started at port 3000...');
(1). controller.js--- 路由集中处理

const fs = require('fs');

// add url-route in /controllers:

function addMapping(router, mapping) {
for (var url in mapping) {
if (url.startsWith('GET ')) {
var path = url.substring(4);
router.get(path, mapping[url]);
console.log(`register URL mapping: GET ${path}`);
} else if (url.startsWith('POST ')) {
var path = url.substring(5);
router.post(path, mapping[url]);
console.log(`register URL mapping: POST ${path}`);
} else if (url.startsWith('PUT ')) {
var path = url.substring(4);
router.put(path, mapping[url]);
console.log(`register URL mapping: PUT ${path}`);
} else if (url.startsWith('DELETE ')) {
var path = url.substring(7);
router.del(path, mapping[url]);
console.log(`register URL mapping: DELETE ${path}`);
} else {
console.log(`invalid URL: ${url}`);
}
}
}

function addControllers(router, dir) {
fs.readdirSync(__dirname + '/' + dir).filter((f) => {
return f.endsWith('.js');
}).forEach((f) => {
console.log(`process controller: ${f}...`);
let mapping = require(__dirname + '/' + dir + '/' + f);
addMapping(router, mapping);
});
}

module.exports = function (dir) {
let
controllers_dir = dir || 'controllers',
router = require('koa-router')();
addControllers(router, controllers_dir);
return router.routes();
};
(2). rest.js--- 支持rest的中间件middleware

a.定义错误码的统一处理

b.统一输出REST

如果每个异步函数都编写下面这样的代码：

// 设置Content-Type:
ctx.response.type = 'application/json';
// 设置Response Body:
ctx.response.body = {
products: products
};
很显然，这样的重复代码很容易导致错误，例如，写错了字符串'application/json'，或者漏写了ctx.response.type = 'application/json'，都会导致浏览器得不到JSON数据。

写这个中间件给ctx添加一个rest()方法，直接输出JSON数据

module.exports = {
APIError: function (code, message) {
this.code = code || 'internal:unknown_error';
this.message = message || '';
},
restify: (pathPrefix) => {
pathPrefix = pathPrefix || '/api/';
return async (ctx, next) => {
if (ctx.request.path.startsWith(pathPrefix)) {
console.log(`Process API ${ctx.request.method} ${ctx.request.url}...`);
ctx.rest = (data) => {
ctx.response.type = 'application/json';
ctx.response.body = data;
}
try {
await next();
} catch (e) {
console.log('Process API error...');
ctx.response.status = 400;
ctx.response.type = 'application/json';
ctx.response.body = {
code: e.code || 'internal:unknown_error',
message: e.message || ''
};
}
} else {
await next();
}
};
}
};
(3). controllers/api.js--- rest api的定义

具体的api定义，这里可以优化下：不同模块建立文件夹，如products/Api.js, car/api.js ...这样更清晰

const products = require('../model/products');

const APIError = require('../rest').APIError;

module.exports = {
'GET /api/products': async (ctx, next) => {
ctx.rest({
products: products.getProducts()
});
},

'POST /api/products': async (ctx, next) => {
var p = products.createProduct(ctx.request.body.name, ctx.request.body.manufacturer, parseFloat(ctx.request.body.price));
ctx.rest(p);
},

'DELETE /api/products/:id': async (ctx, next) => {
console.log(`delete product ${ctx.params.id}...`);
var p = products.deleteProduct(ctx.params.id);
if (p) {
ctx.rest(p);
} else {
throw new APIError('400', 'product not found by id.');
}
}
};
(4). model/products.js--- 具体的model逻辑处理

模拟数据库操作

// store products as database:

var id = 0;

function nextId() {
id++;
return 'p' + id;
}

function Product(name, manufacturer, price) {
this.id = nextId();
this.name = name;
this.manufacturer = manufacturer;
this.price = price;
}

var products = [
new Product('iPhone 7', 'Apple', 6800),
new Product('ThinkPad T440', 'Lenovo', 5999),
new Product('LBP2900', 'Canon', 1099)
];

module.exports = {
getProducts: () => {
return products;
},

getProduct: (id) => {
var i;
for (i = 0; i < products.length; i++) {
if (products[i].id === id) {
return products[i];
}
}
return null;
},

createProduct: (name, manufacturer, price) => {
var p = new Product(name, manufacturer, price);
products.push(p);
return p;
},

deleteProduct: (id) => {
var
index = -1,
i;
for (i = 0; i < products.length; i++) {
if (products[i].id === id) {
index = i;
break;
}
}
if (index >= 0) {
// remove products[index]:
return products.splice(index, 1)[0];
}
return null;
}
};
3、postman调试

npm run dev

postman测试增、查、删

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作者：空谷足音 -จุ
来源：CSDN
原文：https://blog.csdn.net/davidPan1234/article/details/83413958
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