An example of node building a server through express

This article mainly introduces node to build its own server through express. The editor thinks it is quite good. Now I will share it with you and give it as a reference. Let’s follow the editor and take a look.

Preface

In order to simulate the project online, we need a server to provide an API for us to call data. This time I used the express framework to write the API interface. All requests are made through ajax requests to the server to return data. This is the first time I use node to write a backend. It's basically like crossing the river by feeling for the stones. If there are any deficiencies in the article, please point them out.

Install express framework

Portal: express official

Then introduce the middleware that needs to be introduced. Node itself provides some libraries. We can reference it directly through require. For libraries that are not provided, we can also install them through manual npm.

##

var fs = require('fs'); 操作文件模块
var http = require('http'); http模块
var url = require('url');  获取url信息模块
var qs = require('querystring'); 处理url参数模块
var path = require('path'); 文件路径模块
var bodyParser = require('body-parser'); 请求体对象化 （必须）否则后台无法解析前端发送的body内容

Then enable the module directly

app.use(bodyParser.json());

// 访问静态资源文件 这里是访问所有dist目录下的静态资源文件
app.use(express.static(path.resolve(__dirname, '../dist')))
app.use(express.static('public'));

// 因为是单页应用 所有请求都走/dist/index.html
app.get('／', function(req, res) {
 const html = fs.readFile(path.resolve(__dirname, '../dist/index.html'), 'utf-8');
 res.send(html)
});

//处理请求跨域

app.all('*', function(req, res, next) {
 res.header("Access-Control-Allow-Origin", "*");
 res.header("Access-Control-Allow-Headers", "X-Requested-With");
 res.header("Content-Type", "application/json;charset=utf-8");
 res.header("Access-Control-Allow-Headers", "content-type");
 next();
});

After the preparations are done, you can start writing the interface. Regarding the database, you can simulate a json, or you can actually simulate the online database.

The following will be divided into three parts for description-database docking, requested operations, and file request operations.

Database connection

Here I assume that you have installed the mongodb database and enabled it successfully. Read the express tutorial carefully and you will find that the framework provides support for mongodb. Mongodb has many extension plug-ins to use the database, such as mongoose. Here we use mongoskin officially provided by express to link to the database.

$ npm install mongoskin

＃＃＃＃＃官方实例

var db = require('mongoskin').db('localhost:27017/animals');

db.collection('mamals').find().toArray(function(err, result) {
 if (err) throw err;
 console.log(result);
});

After the installation is successful, we first introduce the database used, the code is as follows

##

var db = require('mongoskin').db('mongodb://localhost:27017/blog');
var ObjectId = require('mongodb').ObjectID;

The above code indicates that we successfully connected to the blog database and enabled the private ID. The objectID is the ID automatically added to the data generated by mongodb. It can be used directly. At this point, the database and server have been connected.

Process the request sent by the front end

Process the get request

/**
 * 获取文章信息
 */
app.get('/article/info', function (req, res) {
 >>> 获取请求参数
 var arg = qs.parse(url.parse(req.url).query);
 var id = arg.id;
 >>> 链接数据库根据参数查找文档并返回
 db.collection('articleList').find({ "_id": ObjectId(id)}).toArray(function(err, result) {
  if (err) throw err;
  console.log(result)
  res.end(JSON.stringify(result))
 });
});

The above code implements the processing of a get request, and obtains the parameters of the url through the parameter module. The db is the connected database. Search the data table of 'articleList' based on the ID. After processing, return the data through res.end() to complete the response.

Processing post requests

/**
 * 提交留言信息
 */
app.post('/board/post', function (req, res) {
 >>>> 获取请求参数
 var data = {
  date: req.body.date,
  name: req.body.name,
  content: req.body.content,
  time: req.body.time,
  position: req.body.position
 };
 
 >>> 链接数据库并插入数据
 
 db.collection('board').insert(data, function(err, result) {
  if(err) {
   res.end('Error:'+ err)
  }
  res.end('提交成功')
 });
});

The parameter acquisition of post request is different from get, which can be obtained directly through req.body The request body transmitted by the front end. Get parameters through js objects. Then perform database operations based on the parameters. At this point, the basic requests have been introduced. Let’s talk about how to handle common file operation requirements such as uploading images.

Processing front-end file requests

In order to simplify the operation, we can introduce the multer module to process files, the code is as follows

var multer = require('multer');
var storage = multer.diskStorage({
 //设置上传后文件路径，uploads文件夹会自动创建。
 destination: function (req, file, cb) {
  cb(null, './public/uploads')
 },
 //给上传文件重命名，获取添加后缀名
 filename: function (req, file, cb) {
  var fileFormat = (file.originalname).split(".");
  cb(null, file.fieldname + '-' + Date.now() + "." + fileFormat[fileFormat.length - 1]);
 }
});
／／生成上传模块，让API调用
var upload = multer({
 storage: storage
}).single('file');

The above code has successfully introduced the file upload module. Through this module, we can quickly generate corresponding content. For specific usage methods, you can view the official documentation. After the preparation work is completed, use it in the project:

/**
 * 图片上传
 */
app.post('/upload', function (req, res) {
 upload(req, res, function (err) {
  if (err) {
   console.log(err)
   return
  }
  console.log(req.file)
  res.end(JSON.stringify(req.file))
 })
});

／／图片上传到服务器 ，向客户端返回文件信息
  比如文件的存储位置，之后就可以通过地址访问服务器的图片

/**
 * 图片删除
 */
app.post('/image/delete', function (req, res) {
 fs.unlink(req.body.path, function(err) {
  if (err) {
   return console.error(err);
  }
  res.end("文件删除成功！");
 });
});

To upload pictures here, we directly use the upload module that has been written before. When the interface requests When successful, the file has been uploaded successfully. If you need a preview process, you should not call the upload interface directly. Through the native node fs module, we can also delete and modify the added files.

Going online and the history mode refresh problems encountered after going online

We can regard the online process as changing a computer to run the program. Here I use Alibaba Cloud server. Install a good environment on the cloud server, clone the project into it, install a permanent runtime library such as forever, start ~ ok, and your project will always run. If you need www access, you also need to buy a dns resolution and domain name to point to your server.

As mentioned above, if we run the project locally, it will basically be no problem. But it will be refreshed after the project goes online. Ala? ? 404 what the hell? Open Baidu and check. That's a lot of fire~~ History mode is enabled on the current end, and support for history must also be enabled on the backend. The express environment is as follows:

var history = require('connect-history-api-fallback');
var connect = require('connect');
／／／／／／／
app.use(history());

Update code refresh~OK perfect!

Summary

If you want to learn something well, you need long-term accumulation. As a front-end, some knowledge of server databases can not only help us better communicate with our brothers (back-end), but it is also like a fish in water for the front-end.

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