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This article mainly introduces the example analysis of Express connection MySQL and database connection pool, which is very detailed and has certain reference value. Interested friends must read it!

Express connection MySQL preparation work

Open webstorm New Project and select express to create an express project.

After successful creation, the page is as follows:

You also need to import the mysql module in order to connect to the mysql database.

Create a profile

Create a config file in the project, create a congfigdb.js file in the config file to connect to the database, and write in the file:

Var mysql = {host: "127.0.0.1", / / this is the address of the database user: "root", / / requires the user's name password: "root23", / / user password, if you do not have a password, the direct double quotation marks are database: "info", / / database name port:3306// database port number} module.exports = mysql / / using module.exports to expose the interface file const express = require ('express'); const router = express.Router (); / / Import MySQL module const mysql = require (' mysql'); / / Import configuration file const db = require ('.. / config/configdb'); router.get ('test', (req,res) = > {/ / create database connection object let conn = mysql.createConnection (db) / / query all data conn.query in bookinfo ('select * from student', (err,results,fieldes) = > {/ / fieldes indicates a specific field if (err) {throw err;} res.send (results);}) / / close the database link conn.end ((err) = > {console.log (err);}) module.exports = router

Add to the app.js file when you are finished:

Var dbRouter = require ('. / routes/option') app.use ('/ db',dbRouter)

Test in Postman as follows:

Database connection Pool Technology what is Database connection Pool

Database connection pool is that a sufficient number of database connection objects are established when the program starts, and these connection objects are formed into a pool, and the program dynamically applies, uses and releases the connection objects in the pool.

What is the purpose of the database connection pool?

The connection pool of the database is responsible for allocating, managing, and releasing database connection objects. It allows applications to reuse connection objects from an existing database. Instead of recreating one.

Database connection pool technology example 1, import mysql module var mysql = require ('mysql'); 2, create database connection pool

Create a connection pool

Var pool = mysql.createPool (options)

The options parameter is an object with a number of property configurations that are used to specify various options for uniform use of connections in the connection pool.

/ / create database connection pool const pool = mysql.createPool ({connectionLimit:20, host:'localhost', port:3306, user:'root', password:'123456', database:'info'}) / / Export database connection pool object module.exports = pool

ConnectionLimit: used to specify the maximum number of links in the connection pool, with a default attribute value of 10. 0.

QueueLimit: used to specify the maximum number of connections allowed to be suspended. If the number of suspended connections exceeds this value, an error is thrown immediately. The default property value is 0. Represents the maximum number of connections that are not allowed to be suspended.

MultipleStatements: whether to allow the execution of multiple sql statements. The default is false.

Host: the address of the database server

User: the user name to connect to the database

Password: the password to connect to the database

Database: database name

3. Get the database link object pool.getConnection ((err, conn) = > {if (err) {console.log (err)} else {let sql = 'select * from bookinfo'; conn.query (sql, (err, results) = > {if (err) {console.log (err)} else {res.send (results)) Conn.release ();}})}}) 4. Release the database connection object conn.release (); complete instance const express = require ('express'); const pool = require ('.. / config/dbmysql'); const router = express.Router () / * * http://localhost:3000/dbmysql/books* * / router.get ('/ books', (req,res) = > {/ / get the database connection object pool.getConnection from the database connection pool ((err,conn) = > {if (err) {console.log (err)} else {let sql = 'select * from bookinfo' Conn.query (sql, (err,results) = > {if (err) {console.log (err)} else {res.send (results); conn.release ();}})}) module.exports = router

Result test:

The above is all the contents of the article "sample Analysis of Express connection MySQL and Database connection Pool". Thank you for reading! Hope to share the content to help you, more related knowledge, welcome to follow the industry information channel!

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