javascript - 发送后无法设置 header 。调用 create(data,cb) 时

Question

我是 Node 新手，正在尝试在 mongodb 中创建模型。当我调用 localhost:3000/a 时。我在控制台中两次看到请求也收到错误 Can't set headers after they are sent

module.exports = function(app) {
  app.get('/',function(req,res){
    res.render("adminpanel/panel",{});
  });
  app.get('/a',function (req,res,cb) {
    console.log(req.url)
    var User = app.models.test;
    var user = app.models.test();
    user.username = "admin";
    user.type = "hey";
    user.password = "132";
    user.email = "admin@test.com";
    User.create(user,cb);
    res.send("hey");
  });
};

输出:

output: 
  /a
  /a
  Error: Can't set headers after they are sent.
    at ServerResponse.OutgoingMessage.setHeader (_http_outgoing.js:344:11)
    at ServerResponse.header (E:\workspace\orderapp\node_modules\express       \lib\response.js:718:10)
    at ServerResponse.contentType (E:\workspace\orderapp\node_modules\express\lib\response.js:551:15)
    at ServerResponse.send (E:\workspace\orderapp\node_modules\express\lib\response.js:138:14)
    at E:\workspace\orderapp\server\boot\root.js:14:9
    at Layer.handle [as handle_request] (E:\workspace\orderapp\node_modules\express\lib\router\layer.js:95:5)
    at next (E:\workspace\orderapp\node_modules\express\lib\router\route.js:131:13)
    at Route.dispatch (E:\workspace\orderapp\node_modules\express\lib\router\route.js:112:3)
    at Layer.handle [as handle_request] (E:\workspace\orderapp\node_modules\express\lib\router\layer.js:95:5)
    at E:\workspace\orderapp\node_modules\express\lib\router\index.js:277:22

Answer 1

当您完成请求，然后尝试针对同一请求发送更多内容时，就会发生错误。当有人在异步处理中犯了错误，导致请求对象上发送内容的时间发生错误时，通常会发生这种情况。

我发现您的代码存在两个问题。首先，您尝试从路由处理程序调用 next() ，就好像您尚未真正完成处理请求一样。其次，您在调用 next() 之前发送 res.send()，因为 User.create() 是异步的并且会完成稍后。

我建议你使用这个:

  app.get('/a',function (req,res) {
    console.log(req.url)
    var User = app.models.test;
    var user = app.models.test();
    user.username = "admin";
    user.type = "hey";
    user.password = "132";
    user.email = "admin@test.com";
    User.create(user,function() {
        res.send("hey");
    });
  });