如何使用Express（Node.js）的multer插件？

我不明白为什么我的代码返回错误？

我发送一个jpg文件（Content-Type：multipart / form-data）到localhost:3000/list/upload

也许我错了，但我错误地使用multer插件。

这是我的Express代码：

 var express = require('express'); var path = require('path'); var fs = require('fs'); var logger = require('morgan'); var cookieParser = require('cookie-parser'); var bodyParser = require('body-parser'); var multer = require('multer'); var fileName; var routes = require('./routes/index'); var users = require('./routes/users'); var app = express(); app.set('views', path.join(__dirname, 'views')); app.set('view engine', 'jade'); app.use(logger('dev')); app.use(bodyParser.json()); app.use(bodyParser.urlencoded({ extended: false })); app.use(cookieParser()); app.use(express.static(path.join(__dirname, 'public'))); app.use(bodyParser({uploadDir: path.join(__dirname, 'public/images')})); app.use('/', routes); app.use('/users', users); var m = multer({ dest: './public/images', onFileUploadStart: function (file) { var mt = file.mimetype; if (mt === 'image/png' || mt === 'image/jpg' || mt === 'image/jpeg') { fileName = file.fieldname; } else { fileName = undefined; return false; } } }); app.post('/list/upload', m, function (req, res) { if (fileName) { res.send({ success: true, name: fileName }); fileName = undefined; } else { res.send({ success: false }); } }); // error handling module.exports = app; 

我得到这个错误：

 Multipart: Boundary not found