class XYZ {
constructor(app) {
// app is express object
this.app = app;
this.app.route('/api/url')
.get(this.wrap(this.urlhandler.bind(this)));
// to send error as json -> this never gets invoked ??
this.app.use((err, req, res, next) => {
res.status(400).json({error: err});
next(err);
});
}
// wraps each async route function to handle rejection and throw errors
wrap(fn) {
return function (req, res, next) {
Promise.resolve(fn(req, res, next)).catch(function (err) {
console.log('ERROR OCCURED: > > > > > > > ', err.code);
next(err)
});
}
}
}
每个快速ASYNC路由都被包装以捕获路由处理函数中的任何拒绝或抛出错误。每当有这样的拒绝或错误时 - 包裹被调用很好,我能够看到“ERROR OCCURED>>> ..”的打印。
但是我无法将该错误传递给错误处理程序中间件,我打算发送400 JSON错误。
如何解决上述情况?
答案 0 :(得分:0)
抱歉,我无法隔离示例代码以轻松演示错误。我正在使用mysql,表达 - 与promises和ES6混合。
以下是我遇到的一个问题及其解决方案。
问题:我在初始化路由之前添加了错误处理中间件。最后添加错误中间件解决了它! (Thanks to this stackoverflow question)。
var mysql = require('mysql');
var express = require('express');
var bodyParser = require('body-parser')
var morgan = require('morgan');
//define class
class Sql {
constructor(pool) {
this.pool = pool;
}
exec(query, params) {
let _this = this;
return new Promise(function (resolve, reject) {
_this.pool.query(query, params, function (error, rows, _fields) {
if (error) {
return reject(error);
}
return resolve(rows);
});
});
}
}
//define class
class Api {
constructor(mysqlPool, app) {
this.mysql = new Sql(mysqlPool)
this.app = app;
// this.app.use(this.errMw)
//console.log('IF ERROR MIDDLEWARE IS ADDED HERE - it was NEVER CALLED');
/**************** add middleware and routes ****************/
this.app.get('/', this.asyncWrap(this.root.bind(this)))
this.app.use(this.errMw) // << USE ERROR MIDDLEWARE HERE
}
errMw(err, req, res, next) {
res.status(400).json({error: err});
next(err);
}
asyncWrap(fn) {
return (req, res, next) => {
Promise.resolve(fn(req, res, next))
.catch((err) => {
console.log('err > > > > >', err.message);
next(err);
});
}
}
run(cbk) {
this.app.listen(3000)
}
async root(req, res) {
res.json(await this.mysql.exec('select * from customer', []))
}
}
/**************** START : mysql,express,api -> run ****************/
let args = {}
args['host'] = 'localhost'
args['user'] = 'root'
args['password'] = 'secret'
args['database'] = 'models'
let mysqlPool = mysql.createPool(args)
let app = express()
//app.use(morgan('tiny'))
app.use(bodyParser.json())
app.use(bodyParser.urlencoded({
extended: true
}))
let api = new Api(mysqlPool, app);
api.run()
/**************** END : mysql,express,api -> run ****************/