Build a simple query server using express.

Build a simple query server using express.

This article describes how to use express to set up a simple query server. The details are as follows:

The technology stacks used include express and mysql.

Project Structure:

service--node_modules--app.js--query.js

App. js supports service calling and uses body-parser to process requests.

Query. js allows you to connect to and query databases.

The app. js code is as follows:

Var express = require ('express '); var query = require ('. /query') var bodyParser = require ('body-parser '); var cookieParser = require ('cookie-parser'); var app = express (); app. use (bodyParser. urlencoded ({extended: false}) // The returned object is a key-value pair. When extended is false, the value in the key-value pair is in the 'string' or 'array' format. If it is true, it can be of any data type. App. use (bodyParser. json () // cross-origin support app. all ('*', function (req, res, next) {res. header ("Access-Control-Allow-Origin", "*"); res. header ('access-Control-Allow-Methods ', 'Put, GET, POST, DELETE, options'); res. header ("Access-Control-Allow-Headers", "X-Requested-With"); res. header ('access-Control-Allow-headers', 'content-type'); next () ;}); // log on to the app. post ('/login', (req, res) => {var opts = req. body; query ("SELE CT * FROM 'v _ users' WHERE userAcount =? ", Opts. userName). then (result) => {var response = result [0]; if (opts. password! = Response. u_password) {return res. send ({errorCode: '000000', errorMsg: 'logon password error'})} // generate a simulated logtailken var logtailken = response. userAcount + Math. random () * Math. pow (10, 16) res. send ({logtailken: logtailken}) var server = app. listen (3000, () => {console. log ('success ')})

The query. js code is as follows:

(function() {  var mysql = require('mysql');  // var session = require('cookie-session');  var query = (sql,key) => {    var connection = mysql.createConnection({      host: 'localhost',      user: 'root',      password: 'root123',      database: 'm_users'    });    connection.connect()    var promise = new Promise((resolve,reject)=>{      connection.query(sql,[key], function(error, results, fields) {        if(error){          reject(error)        }else{          resolve(results);        }      });      connection.end();    });    return promise;  }  module.exports = query;})()

Practice summary:

1. Entry-level usage of express and the usage of the body-parser and mysql plug-ins.

2. Try to use Inspector to debug the node program and implement debugger. by the way, I am more accustomed to using gulp for debugging.

3. The difference between Content-Type and the client-side's post interface is as follows:

Content-Type: application/json; charset = UTF-8 parameter placed in requestPayload

Content-Type: Do not set or place the application/x-www-form-urlencoded parameter in Form Data

The above is all the content of this article. I hope it will be helpful for your learning and support for helping customers.