having issues migrating from express 3.x to 4.x

    Failed to load c++ bson extension, using pure JS version

    /home/justhacker/tools/codes/microblog/node_modules/express/lib/express.js:89

    throw new Error('Most middleware (like ' + name + ') is no longer bundle ^

    Error: Most middleware (like session) is no longer bundled with Express and must be

    installed separately. Please see https://github.com/senchalabs/connect#middleware.

    at Function.Object.defineProperty.get (/home/justhacker/tools/codes/microblog/node_modules/express/lib/express.js:89:13)

    at module.exports (/home/justhacker/tools/codes/microblog/node_modules/connect-mongo/lib/connect-mongo.js:30:22)

    at Object. (/home/justhacker/tools/codes/microblog/app.js:14:42)
    at Module._compile (module.js:449:26)
    at Object.Module._extensions..js (module.js:467:10)
    at Module.load (module.js:349:32)
    at Function.Module._load (module.js:305:12)
    at Function.Module.runMain (module.js:490:10)
    at startup (node.js:124:16)
    at node.js:807:3

官方文档。
Middleware
As of 4.x, Express no longer depends on Connect. All of Express' previously included middleware are now in separate repos. Please view the list of middleware. The only included middleware is now express.static().

但是我的代码里面没有用。

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

var util = require('util');

var routes = require('./routes/index');
var users = require('./routes/users');
//var connect = require('connect');
var MongoStore = require('connect-mongodb');
var setting = require('./setting');


var app = express();




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

app.use(favicon());
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded());
//app.use(express.methodOverride());
app.use(cookieParser());
app.use(session({ 
secret: setting.cookieSecret, 
store: new MongoStore({ 
db: setting.db 
}) 
})); 
app.use(express.static(path.join(__dirname, 'public')));

app.use('/', routes);
app.use('/users', users);

/// catch 404 and forwarding 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;

现在报错

Failed to load c++ bson extension, using pure JS version

现在界面显示这个。

Cannot read property 'findOne' of null
undefined

TypeError: Cannot read property 'findOne' of null
at MongoStore.MONGOSTORE.get (/home/justhacker/tools/codes/microblog/nodemodules/connect-mongodb/lib/connect-mongodb.js:115:14)
at Layer.session [as handle] (/home/justhacker/tools/codes/microblog/nodemodules/express-session/index.js:328:11)
at trimprefix (/home/justhacker/tools/codes/microblog/nodemodules/express/lib/router/index.js:226:17)
at /home/justhacker/tools/codes/microblog/nodemodules/express/lib/router/index.js:198:9
at Function.proto.processparams (/home/justhacker/tools/codes/microblog/nodemodules/express/lib/router/index.js:251:12)
at next (/home/justhacker/tools/codes/microblog/nodemodules/express/lib/router/index.js:189:19)
at Layer.cookieParser [as handle] (/home/justhacker/tools/codes/microblog/nodemodules/cookie-parser/index.js:46:5)
at trimprefix (/home/justhacker/tools/codes/microblog/nodemodules/express/lib/router/index.js:226:17)
at /home/justhacker/tools/codes/microblog/nodemodules/express/lib/router/index.js:198:9
at Function.proto.processparams (/home/justhacker/tools/codes/microblog/nodemodules/express/lib/router/index.js:251:12)

---

Error: Most middleware (like session) is no longer bundled with Express and must be
installed separately.

Please see https://github.com/senchalabs/connect#middleware.

npm install express-session

---

express 4.x 分离了middleware，除了static，其他需要自行安装