我總是收到錯誤「錯誤:發送後無法設置標頭。」在調用「res.writeHead(...)」時的連接的第一個回調:Nodejs:在第一個連接回調中連接和「writeHead」
var http = require('http');
var connect = require('connect');
var simpleApp = connect();
simpleApp
.use(function(req, res, next){
res.writeHead(200, { 'content-type': 'text/html' });
res.write('response powered by SIMPLE connect-object as middelware');
console.log('Pre');
next();
console.log('Post');
})
.use(function(req, res, next){
console.log('I am the header guy!');
next();
})
.use('/admin', function(req, res, next){
console.log('someone entered the admin area....');
next();
})
.use(function(req, res){
console.log('reached the tail of the "chain of responsibility!!!');
res.end();
});
http.createServer(simpleApp).listen(process.env.PORT || 3000);
console.log('Running on port "' + (process.env.PORT || 3000) + '"');
// just a save-guard to stop the process after some time...
setTimeout(function(){
process.exit(0);
}, 20000);
這是錯誤消息:
Error: Can't set headers after they are sent.
at ServerResponse.OutgoingMessage.setHeader (http.js:691:11)
at ServerResponse.res.setHeader (C:\Users\drt\SkyDrive\Programmierung\nodejs\silkveil\node_modules\connect\lib\patch.js:63:22)
at next (C:\Users\drt\SkyDrive\Programmierung\nodejs\silkveil\node_modules\connect\lib\proto.js:156:13)
at Object.handle (C:\Users\drt\SkyDrive\Programmierung\nodejs\silkveil\connectSampleApp.js:13:3)
at next (C:\Users\drt\SkyDrive\Programmierung\nodejs\silkveil\node_modules\connect\lib\proto.js:193:15)
at Function.app.handle (C:\Users\drt\SkyDrive\Programmierung\nodejs\silkveil\node_modules\connect\lib\proto.js:201:3)
at Server.app (C:\Users\drt\SkyDrive\Programmierung\nodejs\silkveil\node_modules\connect\lib\connect.js:65:37)
at Server.EventEmitter.emit (events.js:98:17)
at HTTPParser.parser.onIncoming (http.js:2108:12)
當我移動「writeHead」 -code到最後回調一切都很好:
.use(function(req, res){
console.log('reached the tail of the "chain of responsibility!!!');
res.writeHead(200, { 'content-type': 'text/html' });
res.write('response powered by SIMPLE connect-object as middelware');
res.end();
});
所以我的問題是:是否只允許在使用connect時在最後一次回調中使用writeHead/write?
好的,所以在最後一次回調中只能「允許」調用「res.write」!因爲我能夠使用「res.setHeader('content-type','text/html');」在第一個回調中,它正在工作。 – thuld
對,您必須在最後一次回撥之前將回復留在頭部。 – Changgeng
感謝您的回答 – thuld