无法使用Node.js和Express捕获POST参数

我正在尝试一个简单的Node.js + Express RESTful API示例，并且已经创建了一个简单的操作来模拟登录请求。这是我的代码：

app.js

var express = require('express');
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');

var routes = require('./routes/index');
var users = require('./routes/users');

var app = express();

// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');

// uncomment after placing your favicon in /public
//app.use(favicon(__dirname + '/public/favicon.ico'));
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('/', routes);
app.use('/users', users);

// catch 404 and forward to error handler
app.use(function(req, res, next) {
    var err = new Error('Not Found');
    err.status = 404;
    next(err);
});

// error handlers

// development error handler
// will print stacktrace
if (app.get('env') === 'development') {
    app.use(function(err, req, res, next) {
        res.status(err.status || 500);
        res.render('error', {
            message: err.message,
            error: err
        });
    });
}

// production error handler
// no stacktraces leaked to user
app.use(function(err, req, res, next) {
    res.status(err.status || 500);
    res.render('error', {
        message: err.message,
        error: {}
    });
});
module.exports = app;

users.js

var express = require('express');
var router = express.Router();

/* GET users listing. */
router.get('/', function(req, res) {
  res.send('respond with a resource');
});

/* My Login */
router.post('/login', function(req, res){
    var data = {
        user : req.body.user,
        pass : req.body.pass
    };
    res.send(data);
});

module.exports = router;

我正在用邮递员（user = joe，pass = 123456）模拟POST请求，但是我收到一个空{}的响应。已经尝试过此解决方案，但没有成功。如何在Node.js上捕获POST参数？怎么了？

更新我已嵌入我的app.js和users.js代码，以便进行更好的审核。