发布到数据库时,我得到一个 "Can't set headers after they are sent error"
When POSTing to the database, I'm getting a "Can't set headers after they are sent error"
在这个问题中,我发布了从开始到结束进行销售的完整数据流,因为我不知道错误在哪里。在我的应用程序中,我在 Checkout 组件中调用了一个名为 handlePay() 的函数,该函数又调用了一个名为 makeSale() 的动作创建器。 makeSale() 然后向 router.js 中的服务器发出 POST 请求,服务器将使用 mongoose 在数据库中处理此次销售。控制台的错误显示为
"/Users/marcushurney/Desktop/P.O.S./node_modules/mongodb/lib/utils.js:98
process.nextTick(函数() { 抛出错误; });
^
错误:发送后无法设置 headers。
我不确定我与 router.js 或 front-end 中的数据库通信的代码中是否存在此错误。 front-end 上的组件称为 Checkout.jsx,处理销售的函数是 handlePay(),其关联的操作创建者是 makeSale()。
Checkout.jsx
handlePay: function() {
var props = {
user_id: this.props.activeUser._id, //This sale will belong to the user that is logged in (global state)
items: [], //All the items in the cart will be added to the sale below (global state)
total: this.props.cartTotal //Total price of the sale is drawn from the global state
}
this.props.cart.map((product) => {
var item = {};
item.name = product.name;
item.product_id = product._id;
item.cartQuantity = product.cartQuantity;
item.priceValue = product.price;
props.items.push(item);
});
var jsonProps = JSON.stringify(props); //converts properties into json before sending them to the server
this.props.makeSale(jsonProps);
}
actions/index.js
export function makeSale(props) {
var config = {headers: {'authorization' : localStorage.getItem('token')}};
var request = axios.post('/makeSale', props, config); //This will store the sale in the database and also return it
return {
type: MAKE_SALE,
payload: request //Sends sale along to be used in sale_reducer.js
};
}
router.js
//Adds a new sale to the database
//Getting error "can't set headers after they are sent"
app.post('/makeSale', function(req, res, next){
var sale = new Sale();
sale.owner = req.body.user_id;
sale.total = req.body.total;
req.body.items.map((item)=> {
//pushs an item from the request object into the items array contained in the sale document
sale.items.push({
item: item.product_id,
itemName: item.name,
cartQuantity: parseInt(item.cartQuantity), //adds cartQuantity to sale
price: parseFloat(item.priceValue)
});
Product.findById(item.product_id)
.then((product) => {
//finds the item to be sold in the database and updates its quantity field based on the quantity being sold
product.quantity -= item.cartQuantity;
//resets the product's cartQuantity to 1
product.cartQuantity = 1;
product.save(function(err) {
if (err) {
return next(err);
} else {
return next();
// return res.status(200).json(product);
}
});
}, (error) => {
return next(error);
});
});
//gives the sale a date field equal to current date
sale.date = new Date();
//saves and returns the sale
sale.save(function(err) {
if (err) { return next(err); }
return res.status(200).json(sale); //Returns the sale so that it can be used in the sale_reducer.js
});
});
这是mongoose的销售模型--> sale.js
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var SalesSchema = new Schema({
owner: { type: Schema.Types.ObjectId, ref: 'User'},
total: { type: Number, default: 0},
items: [{
item: { type: Schema.Types.ObjectId, ref: 'Product'},
itemName: { type: String, default: "no name provided"},
cartQuantity: { type: Number, default: 1 },
price: { type: Number, default: 0 }
}],
date: Date
});
module.exports = mongoose.model('Sale', SalesSchema);
我很少将 JS 用于后端,但这通常意味着您在已经 sent/sending HTTP body.
之后尝试设置 HTTP headers
基本上:只要确保您的 headers 在您将任何内容打印到屏幕之前被发送就是该错误的意思。
Product.findById
是异步的,最终会多次调用 next()
,这将(很可能)导致多次尝试发送响应,这将导致您遇到的错误看到了。
通常(或总是,可能),您只想为每个中间件调用一次 next()
。
试试这个:
"use strict";
app.post('/makeSale', function(req, res, next){
var sale = new Sale();
sale.owner = req.body.user_id;
sale.total = req.body.total;
return Promise.all(req.body.items.map((item) => {
// pushs an item from the request object into the items array contained in the sale document
sale.items.push({
item: item.product_id,
itemName: item.name,
cartQuantity: parseInt(item.cartQuantity, 10), // adds cartQuantity to sale
price: parseFloat(item.priceValue)
});
return Product.findById(item.product_id).then((product) => {
//finds the item to be sold in the database and updates its quantity field based on the quantity being sold
product.quantity -= item.cartQuantity;
//resets the product's cartQuantity to 1
product.cartQuantity = 1;
return product.save();
});
}))
.then(() => {
//gives the sale a date field equal to current date
sale.date = new Date();
//saves and returns the sale
return sale.save();
})
.then(() => {
return res.status(200).json(sale);
})
.catch(next);
});
在您的路线中,您为每个已保存的产品调用 next()
。您也在呼叫res.status(200).json(sale)
。
调用 next()
告诉 Express 您的路由处理程序对处理请求不感兴趣,因此 Express 会将其委托给下一个匹配的处理程序(或通用的 Not Found 处理程序,如果没有的话)。您不能随后再次致电 next()
,也不能自己发回回复,因为您已经告诉 Express 您不感兴趣。
您应该重写 req.body.items.map(...)
以便它根本不调用 next()
。
一种解决方案是使用 async.map()
。然后,您将在最终回调中调用 next(error)
(如果有) 或 res.json()
。
在这个问题中,我发布了从开始到结束进行销售的完整数据流,因为我不知道错误在哪里。在我的应用程序中,我在 Checkout 组件中调用了一个名为 handlePay() 的函数,该函数又调用了一个名为 makeSale() 的动作创建器。 makeSale() 然后向 router.js 中的服务器发出 POST 请求,服务器将使用 mongoose 在数据库中处理此次销售。控制台的错误显示为
"/Users/marcushurney/Desktop/P.O.S./node_modules/mongodb/lib/utils.js:98 process.nextTick(函数() { 抛出错误; }); ^
错误:发送后无法设置 headers。
我不确定我与 router.js 或 front-end 中的数据库通信的代码中是否存在此错误。 front-end 上的组件称为 Checkout.jsx,处理销售的函数是 handlePay(),其关联的操作创建者是 makeSale()。
Checkout.jsx
handlePay: function() {
var props = {
user_id: this.props.activeUser._id, //This sale will belong to the user that is logged in (global state)
items: [], //All the items in the cart will be added to the sale below (global state)
total: this.props.cartTotal //Total price of the sale is drawn from the global state
}
this.props.cart.map((product) => {
var item = {};
item.name = product.name;
item.product_id = product._id;
item.cartQuantity = product.cartQuantity;
item.priceValue = product.price;
props.items.push(item);
});
var jsonProps = JSON.stringify(props); //converts properties into json before sending them to the server
this.props.makeSale(jsonProps);
}
actions/index.js
export function makeSale(props) {
var config = {headers: {'authorization' : localStorage.getItem('token')}};
var request = axios.post('/makeSale', props, config); //This will store the sale in the database and also return it
return {
type: MAKE_SALE,
payload: request //Sends sale along to be used in sale_reducer.js
};
}
router.js
//Adds a new sale to the database
//Getting error "can't set headers after they are sent"
app.post('/makeSale', function(req, res, next){
var sale = new Sale();
sale.owner = req.body.user_id;
sale.total = req.body.total;
req.body.items.map((item)=> {
//pushs an item from the request object into the items array contained in the sale document
sale.items.push({
item: item.product_id,
itemName: item.name,
cartQuantity: parseInt(item.cartQuantity), //adds cartQuantity to sale
price: parseFloat(item.priceValue)
});
Product.findById(item.product_id)
.then((product) => {
//finds the item to be sold in the database and updates its quantity field based on the quantity being sold
product.quantity -= item.cartQuantity;
//resets the product's cartQuantity to 1
product.cartQuantity = 1;
product.save(function(err) {
if (err) {
return next(err);
} else {
return next();
// return res.status(200).json(product);
}
});
}, (error) => {
return next(error);
});
});
//gives the sale a date field equal to current date
sale.date = new Date();
//saves and returns the sale
sale.save(function(err) {
if (err) { return next(err); }
return res.status(200).json(sale); //Returns the sale so that it can be used in the sale_reducer.js
});
});
这是mongoose的销售模型--> sale.js
var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var SalesSchema = new Schema({
owner: { type: Schema.Types.ObjectId, ref: 'User'},
total: { type: Number, default: 0},
items: [{
item: { type: Schema.Types.ObjectId, ref: 'Product'},
itemName: { type: String, default: "no name provided"},
cartQuantity: { type: Number, default: 1 },
price: { type: Number, default: 0 }
}],
date: Date
});
module.exports = mongoose.model('Sale', SalesSchema);
我很少将 JS 用于后端,但这通常意味着您在已经 sent/sending HTTP body.
之后尝试设置 HTTP headers基本上:只要确保您的 headers 在您将任何内容打印到屏幕之前被发送就是该错误的意思。
Product.findById
是异步的,最终会多次调用 next()
,这将(很可能)导致多次尝试发送响应,这将导致您遇到的错误看到了。
通常(或总是,可能),您只想为每个中间件调用一次 next()
。
试试这个:
"use strict";
app.post('/makeSale', function(req, res, next){
var sale = new Sale();
sale.owner = req.body.user_id;
sale.total = req.body.total;
return Promise.all(req.body.items.map((item) => {
// pushs an item from the request object into the items array contained in the sale document
sale.items.push({
item: item.product_id,
itemName: item.name,
cartQuantity: parseInt(item.cartQuantity, 10), // adds cartQuantity to sale
price: parseFloat(item.priceValue)
});
return Product.findById(item.product_id).then((product) => {
//finds the item to be sold in the database and updates its quantity field based on the quantity being sold
product.quantity -= item.cartQuantity;
//resets the product's cartQuantity to 1
product.cartQuantity = 1;
return product.save();
});
}))
.then(() => {
//gives the sale a date field equal to current date
sale.date = new Date();
//saves and returns the sale
return sale.save();
})
.then(() => {
return res.status(200).json(sale);
})
.catch(next);
});
在您的路线中,您为每个已保存的产品调用 next()
。您也在呼叫res.status(200).json(sale)
。
调用 next()
告诉 Express 您的路由处理程序对处理请求不感兴趣,因此 Express 会将其委托给下一个匹配的处理程序(或通用的 Not Found 处理程序,如果没有的话)。您不能随后再次致电 next()
,也不能自己发回回复,因为您已经告诉 Express 您不感兴趣。
您应该重写 req.body.items.map(...)
以便它根本不调用 next()
。
一种解决方案是使用 async.map()
。然后,您将在最终回调中调用 next(error)
(如果有) 或 res.json()
。