ExpressJS 4在res.send()之后执行函数

Question

我是 NodeJS 和异步编程的新手。我使用express作为我的应用程序的基础，实际上只有一个路由服务页面并接受从表单上传的内容。我想在文件上传后向外部服务发出 POST 请求。然而，尝试在 res.send(200) 之后执行任何代码会导致以下错误消息Error: Can't set headers after they are sent.

我正在使用请求包将帖子发送到外部服务。

var express = require('express');
var router = express.Router();
var util = require("util");
var request = require("request");

/* POST uploads. */
router.post('/', function(req, res, next) {
    console.log("LOG:" + util.inspect(req.files));
    res.send('respond with a resource');
    postFile(req.files.file.path);
});

var postFile = function(path) {
    var opts = {
        method: 'POST',
        uri: 'https://example.com/api/files.upload',
        formData: {
            token: "xxx",
            file: fs.createReadStream(req.files.file.path)
        }
    }

    // console.log("LOG:\n" + util.inspect(opts));

    request.post(opts, function(error, response, body) {
        if (error) {
            console.log("ERROR LOG: " + util.inspect(error));
        } else {
            console.log("RESPONSE LOG:" + util.inspect(response));
        }
    });
}

module.exports = router;

postFile 函数本身工作得很好，甚至在 res.send 之后直接添加 console.log 也会导致相同的错误。响应发送到客户端后，如何继续在服务器上执行代码？

节点输出日志：

POST /uploads 200 85.201 ms - 23 Error: Can't set headers after they are sent. at ServerResponse.OutgoingMessage.setHeader (_http_outgoing.js:335:11) at ServerResponse.header (/Users/jason/dev/test/file-share/node_modules/express/lib/response.js:700:10) at ServerResponse.send (/Users/jason/dev/test/file-share/node_modules/express/lib/response.js:154:12) at fn (/Users/jason/dev/test/file-share/node_modules/express/lib/response.js:934:10) at View.exports.renderFile [as engine] (/Users/jason/dev/test/file-share/node_modules/jade/lib/index.js:374:12) at View.render (/Users/jason/dev/test/file-share/node_modules/express/lib/view.js:93:8) at EventEmitter.app.render (/Users/jason/dev/test/file-share/node_modules/express/lib/application.js:566:10) at ServerResponse.res.render (/Users/jason/dev/test/file-share/node_modules/express/lib/response.js:938:7) at /Users/jason/dev/test/file-share/app.js:58:7 at Layer.handle_error (/Users/jason/dev/test/file-share/node_modules/express/lib/router/layer.js:58:5)

Answer 1

下面的代码没有任何问题，响应请求后就可以执行代码了。您只是无法再次发送标头。

router.post('/', function(req, res, next) {
  console.log("LOG:" + util.inspect(req.files));
  res.send('respond with a resource');
  postFile(req.files.file.path);
});

使用POST 或 GET请求不会响应您的请求，除非您愿意。