In express 4.x req.body is undefined

I just moved to express.js 4.8.7 from 3.x. I am getting error in express 4.x, "req.body" is undefined.

When I google it. I found that, I have to install "body-parser' module. Even after installing "body-parser' module, I am getting "req.body" undefined. I am not sure what I need to do. Below is my app.js code

var express = require('express')
, path = require('path')
, redis = require("redis")
, mongoose = require('mongoose')
, favicon = require('serve-favicon')
, compression = require('compression')
, bodyParser = require('body-parser')
, methodOverride = require('method-override')
, errorHandler = require('errorhandler')
, cookieParser = require('cookie-parser')
, morgan  = require('morgan')
, multer  = require('multer')
, session = require('express-session');

var app = express();
var router = express.Router();
router.use(function(req, res, next) {
  console.log('%s %s %s', req.method, req.url, req.path);
  next();
});
var routes = require('./routes')(app);



mongoose.connect('mongodb://localhost/abc');

app.set('port', process.env.PORT || 3000);
app.set('views', __dirname + '/views');
app.set('view engine', 'jade');
app.use(favicon(__dirname + '/public/img/favicon.ico'));
app.use(morgan('dev'));
app.use(methodOverride());
app.use(session({resave: true, saveUninitialized: true, secret: 'uwotm8'}));
app.use(bodyParser.urlencoded({extended: true}));
app.use(bodyParser.json());
app.use(bodyParser.json({ type: 'application/vnd.api+json' }));
app.use(multer({ dest: './uploads/'}));
app.use(methodOverride('X-HTTP-Method'));
app.use(methodOverride('X-HTTP-Method-Override'));
app.use(methodOverride('X-Method-Override'));
app.use(compression({'threshold': 512}));

app.use(express.static(path.join(__dirname, 'public')));

if ('development' == app.get('env')) {
  app.use(errorHandler());
}
app.listen(app.get('port'), function(){
  console.log('Express server listening on port ' + app.get('port'));
});

Error happends in my router callback function.

app.route('/xhr/abc').post(function (req, res) {
    if (req.xhr) {
        var language = req.headers["accept-language"];
...
        var reqBody = req.body;
...
}