FIREBASE WARNING: Exception was thrown by user cal

2019-05-12 01:09发布

站内问答 / 前端开发
1411 1 5

We are developing an app where we are using Firebase as a database and express as the middleware/backend for routing our RESTful API's which is used by our Front-end developed in Reactjs.

Below is what our server.js file looks like:

var express = require('express');
var app = express();

//Used for getting POST variables from forms as well as query parameters
var bodyParser = require('body-parser');
var validator = require('express-validator');

//Contains all the routes
var routes = require('./routes/routes');
var path = require('path');

//Used for serving jade files
app.set('view engine', 'jade');
//For serving static resources like scripts, styleSheets, html
app.use(express.static(__dirname + '/views'));

app.all('/*', function(req, res, next) {
 res.header("Access-Control-Allow-Origin", "*");
 res.header("Access-Control-Allow-Headers", "X-Requested-With, Content-Type, Accept");
 res.header("Access-Control-Allow-Methods", "POST, GET");
 next();
});

// configure app to use bodyParser()
// this will let us get the data from a POST
app.use(bodyParser.urlencoded({ extended: true }));
app.use(bodyParser.json());

app.use(validator({
    customValidators: {
        onlyAlphabets: function(value) {
            if (value.match('^[a-zA-Z ]*$')) {
                return true;
            } else {
                return false;
            }
        },
        password: function(value) {
            if (value.length >= 6 && value.length <=25 && value.match('^[\x20-\x7F]*$')) {
                return true;
            } else {
                return false;
            }
        }
    }
}));
app.use(routes);

var port = process.env.PORT || 8080; //Set our port

app.listen(port);
console.log('Magic happens on port ' + port);

Below is the code for routing which is present in route.js:

var express = require('express');
var views = __dirname;
// Node.js path library - https://nodejs.org/api/path.html
var path = require('path');
var Firebase = require("firebase");
var myFirebaseRef = new Firebase("https://crackling-inferno-8454.firebaseio.com/vendor_details");
var router = express.Router();
//Password Encryption and decryption helpers
var hashFunction = require('../helpers/encrypt');


// middleware to use for all requests
router.use(function(req, res, next) {
  // do logging
  console.log('Something is happening.');
  next(); // make sure we go to the next routes and don't stop here
});

router.get('/', function(req, res) {
  res.render('vendor_form');
});

router.route('/get_vendors').get(function(request, response) {
    myFirebaseRef.on("value", function(snapshot) {
        var store = snapshot.val();
        // Looping to get the firebaseId generated while push
        for(var key in store){
            store[key].id = key;    //  Store firebaseID generated during push to store in JSON object
        }
        response.send(Object.keys(store).map(function(k) { return store[k]; }));
    }, function (errorObject) {
        response.send("The read failed: " + errorObject.code);
    });
});

router.route('/post_vendor').post(function(request, response) {

    request.checkBody({
        'vendor_name': {
            notEmpty : {
                errorMessage: 'Please enter a vendor\'s name'
            },
            onlyAlphabets : {
                errorMessage: 'Please enter only alphabets'
            }
        },
        'enterprise_name': {
            notEmpty : {
                errorMessage: 'Please enter an enterprise\'s name'
            },
            onlyAlphabets : {
                errorMessage: 'Please enter only alphabets'
            }
        },
        'vendor_email': {
            notEmpty : {
                errorMessage: 'Please enter your email address'
            },
            isEmail : {
                errorMessage: 'please enter an appropriate email format'
            }
        },
        'vendor_password': {
            notEmpty : {
                errorMessage: 'Please enter a password'
            },
            password: {
                errorMessage: 'Password length should be between 6-25 characters'
            }
        },
        'food_preference': {
            notEmpty: {
                errorMessage: 'You must select atleast one food preference'
            }
        }
    });

    var errors = request.validationErrors();

    // var onComplete = function(error) {
    //  if (error) {
    //      response.send('Failed to add stats to the database');
  //     return false;
    //  } else {
    //      // response.render('vendor_form', { success: true });
    //      response.send('Success');
  //     return true;
    //  }
    // };

    if (errors) {
        response.send(errors);
        // response.render('vendor_form', { error: errors });
        return false;
    } else {
        myFirebaseRef.push().set({
            'id': Firebase.ServerValue.TIMESTAMP,
            'vendor_name': request.body.vendor_name,
            'enterprise_name': request.body.enterprise_name,
            'vendor_email': request.body.vendor_email,
            'vendor_password': hashFunction.encrypt(request.body.vendor_password),
            'food_preference': request.body.food_preference
        }, function(err) {
      if (err) {
        response.send('Failed to add stats to the database');
      } else {
        response.send('Success');
      }
    });
    return true;
    }
});

module.exports = router;

Below is the code for we added in the front-end for posting data. We are also using whatwg-fetch package:

httpservice.js:

var Fetch = require('whatwg-fetch');
var baseUrl = 'http://192.168.1.134:8080';

var Service = {
  get: function(url) {
    console.log('MAKING A GET REQUEST');
    return fetch(baseUrl + url)
    .then(function(response) {
      return response.json();
    });
  },

  post: function(url, postData) {
    console.log('MAKING A POST REQUEST');
    return fetch(baseUrl + url, {
      headers: {

        'Content-Type': 'application/json'
      },
      method: 'POST',
      body: JSON.stringify(postData)
    }).then(function(response) {
      return response;
    });
  }
}

module.exports = Service;

VendorForm.js (React component file)

HTTP.post('/post_vendor', httpRequestBody)
.then(function(response) {
      console.log(response);
 }.bind(this));

We start our server which provides RESTful API developed in FIREBASE + EXPRESS through nodemon. This is the error that we are receiving when we post our:

FIREBASE WARNING: Exception was thrown by user callback. Error: Can't set headers after they are sent.
    at ServerResponse.OutgoingMessage.setHeader (_http_outgoing.js:344:11)
    at ServerResponse.header (/var/www/tutorials/express_firebase/node_modules/express/lib/response.js:718:10)
    at ServerResponse.send (/var/www/tutorials/express_firebase/node_modules/express/lib/response.js:163:12)
    at ServerResponse.json (/var/www/tutorials/express_firebase/node_modules/express/lib/response.js:249:15)
    at ServerResponse.send (/var/www/tutorials/express_firebase/node_modules/express/lib/response.js:151:21)
    at /var/www/tutorials/express_firebase/routes/routes.js:30:12
    at /var/www/tutorials/express_firebase/node_modules/firebase/lib/firebase-node.js:200:710
    at ec (/var/www/tutorials/express_firebase/node_modules/firebase/lib/firebase-node.js:52:165)
    at ac (/var/www/tutorials/express_firebase/node_modules/firebase/lib/firebase-node.js:31:216)
    at bc (/var/www/tutorials/express_firebase/node_modules/firebase/lib/firebase-node.js:30:1259)
    at Ji.h.Mb (/var/www/tutorials/express_firebase/node_modules/firebase/lib/firebase-node.js:220:440)
    at X.set (/var/www/tutorials/express_firebase/node_modules/firebase/lib/firebase-node.js:256:335)
    at /var/www/tutorials/express_firebase/routes/routes.js:96:24
    at Layer.handle [as handle_request] (/var/www/tutorials/express_firebase/node_modules/express/lib/router/layer.js:95:5)
    at next (/var/www/tutorials/express_firebase/node_modules/express/lib/router/route.js:131:13)
    at Route.dispatch (/var/www/tutorials/express_firebase/node_modules/express/lib/router/route.js:112:3) 
/var/www/tutorials/express_firebase/node_modules/firebase/lib/firebase-node.js:52
(d="0"+d),c+=d;return c.toLowerCase()}var zd=/^-?\d{1,10}$/;function td(a){return zd.test(a)&&(a=Number(a),-2147483648<=a&&2147483647>=a)?a:null}function ec(a){try{a()}catch(b){setTimeout(function(){R("Exception was thrown by user callback.",b.stack||"");throw b;},Math.floor(0))}}function S(a,b){if(t(a)){var c=Array.prototype.slice.call(arguments,1).slice();ec(function(){a.apply(null,c)})}};function Ad(a){var b={},c={},d={},e="";try{var f=a.split("."),b=Pb(id(f[0])||""),c=Pb(id(f[1])||""),e=f[2],d=c.d||{};delete c.d}catch(g){}return{oh:b,Dc:c,data:d,ah:e}}function Bd(a){a=Ad(a).Dc;return"object"===typeof a&&a.hasOwnProperty("iat")?z(a,"iat"):null}function Cd(a){a=Ad(a);var b=a.Dc;return!!a.ah&&!!b&&"object"===typeof b&&b.hasOwnProperty("iat")};function Dd(a){this.Y=a;this.g=a.n.g}function Ed(a,b,c,d){var e=[],f=[];Na(b,function(b){"child_changed"===b.type&&a.g.Ad(b.Le,b.Ma)&&f.push(new H("child_moved",b.Ma,b.Ya))});Fd(a,e,"chi

Error: Can't set headers after they are sent.
    at ServerResponse.OutgoingMessage.setHeader (_http_outgoing.js:344:11)
    at ServerResponse.header (/var/www/tutorials/express_firebase/node_modules/express/lib/response.js:718:10)
    at ServerResponse.send (/var/www/tutorials/express_firebase/node_modules/express/lib/response.js:163:12)
    at ServerResponse.json (/var/www/tutorials/express_firebase/node_modules/express/lib/response.js:249:15)
    at ServerResponse.send (/var/www/tutorials/express_firebase/node_modules/express/lib/response.js:151:21)
    at /var/www/tutorials/express_firebase/routes/routes.js:30:12
    at /var/www/tutorials/express_firebase/node_modules/firebase/lib/firebase-node.js:200:710
    at ec (/var/www/tutorials/express_firebase/node_modules/firebase/lib/firebase-node.js:52:165)
    at ac (/var/www/tutorials/express_firebase/node_modules/firebase/lib/firebase-node.js:31:216)
    at bc (/var/www/tutorials/express_firebase/node_modules/firebase/lib/firebase-node.js:30:1259)
    at Ji.h.Mb (/var/www/tutorials/express_firebase/node_modules/firebase/lib/firebase-node.js:220:440)
    at X.set (/var/www/tutorials/express_firebase/node_modules/firebase/lib/firebase-node.js:256:335)
    at /var/www/tutorials/express_firebase/routes/routes.js:96:24
    at Layer.handle [as handle_request] (/var/www/tutorials/express_firebase/node_modules/express/lib/router/layer.js:95:5)
    at next (/var/www/tutorials/express_firebase/node_modules/express/lib/router/route.js:131:13)
    at Route.dispatch (/var/www/tutorials/express_firebase/node_modules/express/lib/router/route.js:112:3)
[nodemon] app crashed - waiting for file changes before starting...

As per the error, we know that some callback is setting the header twice but not sure how is it happening. Been through few stack overflow questions but still didn't find the solution. Any help would be appreciated. Thanks in anticipation.

1条回答
爱情/是我丢掉的垃圾
2楼-- · 2019-05-12 01:46

If you see your stack trace

at /var/www/tutorials/express_firebase/routes/routes.js:30:12

Which is line 30 in file route.js

response.send(Object.keys(store).map(function(k) { return store[k]; }));

You need to change method on for once, otherwise your callback function gets triggered every time there is an update to your data,

router.route('/get_vendors').get(function(request, response) {
  myFirebaseRef.on("value", function(snapshot) {

breaking your response when you call post method since headers are already sent in line 30.

See reference https://firebase.google.com/docs/database/server/retrieve-data#section-reading-once

Basically what you are doing with the once method is removing the callback immediately after value is read.

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