A brief discussion on the types of node.js middleware

Overview
1. Application-level middleware
2. Built-in middleware
3. Third-party middleware

(1) body-parser, parses post request data into objects
(2) mysql module

Overview

Node middleware is the function of encapsulating http requests in the program. Node middleware is executed in the pipeline. Middleware sits on top of the client/server operating system and manages computer resources and network communications.

Middleware serves the main logical business and can be divided into: application-level middleware, routing-level middleware, built-in middleware, third-party middleware, and error-level middleware.

1. Application-level middleware

Each middleware calls a function and needs to be used with other middleware or routing.

server (function) intercepts all routes

server.use('/reg', function); intercept specific routes

const express = require('express');
var server = express();
server.listen(3000);
//Middleware interception registration route/reg
server.use('/reg',(req,res,next)=>{
    console.log('Registration verification');
    next();
});

server.use('/login',(req,res)=>{
    console.log('Log recorded');
})
server.get('/reg',(req,res,next)=>{
    res.send('Registration successful');
    next();
});

server.get('/login',(req,res)=>{
    res.send('Login successful');
})

2. Built-in middleware

server.use(express.static('目录'))

Host static resource files in a certain directory. If the browser requests static resources, it will automatically search in this directory.

3. Third-party middleware

(1) body-parser, parses post request data into objects

const express = require('express');
//Introduce body-parser middleware const bodyParser=require('body-parser');

var server = express();
server.listen(3000);
// Host static resources to public
server.use(express.static('./public'));

//Use body-parser middleware to parse the post request data into an object //Extended Whether to use the extended qs module to parse into an object //If false, do not use it, and use the querystring module instead server.use(bodyParser.urlencoded(
    {extended:false}
))

server.post('/mylogin',(req,res)=>{
    console.log(req.body);
    res.send('Login successful');
})

(2) mysql module

Normal connection

//Introduce the mysql module const mysql =require('mysql');
//1. Normal connection //1.1 Create a connection var connection = mysql.createConnection({
    host:'127.0.0.1',
    port:'3306',
    user:'root',
    password:'1234',
    database:'tedu'
});
//1.2 Execute connection connection.connect();
//Execute SQL statement connection.query('select * from emp',(err,result)=>{
    if(err) throw err;
    console.log(result);
});
//Close the connectionconnection.end();

Connection Pool

const mysql = require('mysql');
//Use connection pool //Create connection pool object var pool = mysql.createPool(
    {
        host:'127.0.0.1',
        port:'3306',
        user:'root',
        password:'1234',
        database:'tedu',
        connectionLimit:20
    }
);
//Execute SQL statement pool.query('select * from emp where eid=2',(err,result)=>{
    if(err) throw err;
    console.log(result);
})
const mysql = require('mysql');
var pool = mysql.createPool({
    'host':'127.0.0.1',
    port:'3306',
    user:'root',
    password:'1234',
    database:'tedu',
    connectionLimit:20
})
//Use placeholders to insert data // pool.query("insert into emp values(?,?,?,?,?,?)",[null,'yt','1','1995-12-24','9000','20'],(err,result)=>{
// if(err) throw err;
// console.log(result);
// });
//Use object to insert data//var emp={
// eid:null,
// ename:'html',
// sex:1,
// birthday:'1995-12-25',
//salary:10000,
//deptid:30
// }
// pool.query('insert into emp set ?',[emp],(err,result)=>{
// if(err) throw err;
// console.log(result);
// })
//Use the placeholder to delete the data numbered 10 pool.query('delete from emp where eid=?',[10],(err,result)=>{
    if(err) throw err;
    console.log(result);
    if(result.affectedRows>0){
        console.log('Deleted successfully');
    }
    else{
        console.log('deletion failed');
    }
})

The above is a brief discussion of the detailed types of node.js middleware. For more information about node.js middleware, please pay attention to other related articles on 123WORDPRESS.COM!

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