This article mainly introduces a brief discussion of database exception handling in NodeJs. The editor thinks it is quite good, so I will share it with you now and give it as a reference. Let’s follow the editor to take a look, I hope it can help everyone.
NodeJs version: 4.4.4
Database link error
Using nodejs to handle exceptions is the most troublesome, here I will ignore the ## provided by nodejs #domain and some third-party libraries specifically handle things. Operating the database is a commonly used function for us. Through callbacks, we will have a lot of err here.
var pool = require('../db.js'); var runtimeLog = require('../log.js').getLogger('runlog'); var Promise = require('bluebird'); function queryPromise(queryString) { return new Promise(function(resolve, reject) { pool.getConnection(function(err, connection) { //connection.query(queryString, function(err, rows, fields) { // if (!err) { // resolve(rows); // } else { // runtimeLog.error(err) // reject(err) // } // connection.release(); //}); }) }) } module.exports = function() { return new Promise(function(resolve, reject) { queryPromise("select * from wb123_home_map GROUP BY onestair") .then(function(results){ resolve(results); }) .catch(function(err){ runtimeLog.error(err) }) }) }
##
module.exports = { host: '192.168.6.101', database: 'web123', user: 'root', password: 'passw0rd', protocol: 'mysql', port: '330666', query: {pool: true} }
Here we use promise, so in the exported function, we use catch, which will catch the error in the queryPromise function and print it to the log.
[2017-01-05 13:27:59.648] [ERROR] runlog - [err] [RangeError: port should be >= 0 and < 65536: 330666] RangeError: port should be >= 0 and < 65536: 330666 ...
Let’s modify the code, fill in the database link correctly, and modify the sql statement to Wrong statement.
var pool = require('../db.js'); var runtimeLog = require('../log.js').getLogger('runlog'); var Promise = require('bluebird'); function queryPromise(queryString) { return new Promise(function(resolve, reject) { pool.getConnection(function(err, connection) { connection.query(queryString, function(err, rows, fields) { //if (err) throw err; if (!err) { resolve(rows); } else { reject(err) } connection.release(); }); }) }) } module.exports = function() { return new Promise(function(resolve, reject) { queryPromise("select * from wb123_home_map GROUP BY onestairs") .then(function(results){ resolve(results); }) .catch(function(err){ runtimeLog.error('[err]',err) }) }) }
[2017-01-05 14:40:14.518] [ERROR] runlog - [err] { [Error: ER_BAD_FIELD_ERROR: Unknown column 'onestairs' in 'group statement'] code: 'ER_BAD_FIELD_ERROR', errno: 1054, sqlState: '42S22', index: 0 } Error: ER_BAD_FIELD_ERROR: Unknown column 'onestairs' in 'group statement' at Query.Sequence._packetToError (E:\zz\zz_wb123\manage\trunk\code\nod ....
So if Promise is used, we can directly catch the exception thrown below in catch. There is no need to log exceptions in the queryPromise function.
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