[英]Can't set headers after they are sent in express js
我环顾了这个问题的先前答案,但是我不明白如果在多个路径中都有res.send()
,为什么会出现此错误。
我的代码是这样的(expressjs 4.13):
var user ={
username: "some",
password: "a"
}
router.post('/login', authenticate, function (req, res) {
//if it passes the middleware, send back the user
var token = jwt.sign({
username: user.username
}, jwtSecret);
res.send({
token: token,
user: user
});
});
function authenticate(req, res, next) {
var body = req.body;
var username = body.username, password = body.password;
//if nothing is sent
if(!username || !password){
res.status(400).end('Must send a user and pass');
}
//if incorrect credentials are sent
if(username !== user.username || password !== user.password){
res.status(401).end("Incorrect credentials");
}
//if it reaches here, it means credentials are correct
next();
}
当我没有从前端发送任何内容时,我会收到400和错误消息,但是服务器显示如下:
POST /apis/auth/login 401 0.841 ms - -
Error: Can't set headers after they are sent.
at ServerResponse.OutgoingMessage.setHeader (_http_outgoing.js:346:11)
at ServerResponse.header (/home/vivek/dev/qwiksplit/jsback/node_modules/express/lib/response.js:718:10)
at ServerResponse.json (/home/vivek/dev/qwiksplit/jsback/node_modules/express/lib/response.js:246:10)
at ServerResponse.send (/home/vivek/dev/qwiksplit/jsback/node_modules/express/lib/response.js:151:21)
at /home/vivek/dev/qwiksplit/jsback/app.js:81:9
at Layer.handle_error (/home/vivek/dev/qwiksplit/jsback/node_modules/express/lib/router/layer.js:71:5)
at trim_prefix (/home/vivek/dev/qwiksplit/jsback/node_modules/express/lib/router/index.js:310:13)
at /home/vivek/dev/qwiksplit/jsback/node_modules/express/lib/router/index.js:280:7
at Function.process_params (/home/vivek/dev/qwiksplit/jsback/node_modules/express/lib/router/index.js:330:12)
at next (/home/vivek/dev/qwiksplit/jsback/node_modules/express/lib/router/index.js:271:10)
我不确定发送响应后如何设置标题。
确保退货!
return res.status(400).end('Must send a user and pass');
在中间件函数中,需要确保已发送响应后未调用next()
(例如,通过调用res.send()
, res.end()
或类似方法)。
最简单的解决方案是在发送响应后立即从中间件返回:
function authenticate(req, res, next) {
var body = req.body;
var username = body.username, password = body.password;
if(!username || !password){
res.status(400).end('Must send a user and pass');
return; // <-----
}
if(username !== user.username || password !== user.password){
res.status(401).end("Incorrect credentials");
return; // <-----
}
next();
}
您缺少一些return语句。 如果您不从函数status
返回,并且多次在response
对象上调用send
,并且最后还要调用next
,那么即将到来的中间件也将在响应上运行。
function authenticate(req, res, next) {
var body = req.body;
var username = body.username, password = body.password;
//if nothing is sent
if(!username || !password){
res.status(400).end('Must send a user and pass');
return;
}
//if incorrect credentials are sent
if(username !== user.username || password !== user.password){
res.status(401).end("Incorrect credentials");
return;
}
//if it reaches here, it means credentials are correct
next();
}
请确保在此代码后添加return语句
res.status(400).end('Must send a user and pass');
有可能
return; or return res.status(400).end('Must send a user and pass');
只要在该行之后返回任何内容,此后基本上就停止执行代码。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.