在连接的第一个回调中调用“res.writeHead(...)”时,我总是收到错误“错误:发送后无法设置标头。 ”
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);
这是错误消息:
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)
当我将“writeHead”代码移动到最后一个回调中时,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();
});
所以我的问题是:是否只允许在使用连接时在最后一个回调中使用 writeHead /write?