Why does the call to node.js body-parser fail despite the fact that I have installed it?

Question

I'm beginning to learn node.js and trying to work out how to get the contents of a POST request. I am trying to follow the instructions in this post. So far I have successfully installed node.js (on Windows 7) and express, and been able to get my very first script to work. However my problem comes when I try to use body-parser. I have installed it and it appears to be there

Here is the code of the node.js script

var express = require('express');
var bodyParser = require('body-parser');
var app = express();
app.use( bodyParser.json() );       // to support JSON-encoded bodies
app.use(express.json());       // to support JSON-encoded bodies

app.get('/', function(req, res) {
    res.setHeader('Content-Type', 'text/plain');
    res.end('Vous êtes à l\'accueil');
});

app.get('/user/:usernum', function(req, res) {
    res.setHeader('Content-Type', 'text/plain');
    res.end('You are on page USER with n° : ' + req.params.usernum);
});

// https://stackoverflow.com/questions/5710358/how-to-get-post-a-query-in-express-js-node-js
app.post('/adonis', function(req, res) {
    res.setHeader('Content-Type', 'text/plain');
    console.log(req.body.title);
//    res.write(JSON.stringify(req));
    res.end('Hopefully I stringified a POST');
});

// ... Tout le code de gestion des routes (app.get) se trouve au-dessus

app.use(function(req, res, next){
    res.setHeader('Content-Type', 'text/plain');
    res.status(404).send('Page introuvable !');
});

app.listen(8091);

Yet when I run it, node.js throws an error saying "cannot find module body-parser". What have I done wrong?

As per @Kale's and others' suggestions I tried installing body-parser locally, but this does not seem to help since now my script gives the following message:

Error: Most middleware (like json) is no longer bundled with Express and must be installed separately. Please see https://github.com/senchalabs/connect#middleware.
at Function.Object.defineProperty.get (d:\smartguide\nodejs\node_modules\express\lib\express.js:99:13)
at Object.<anonymous> (d:\smartguide\nodejs\oc1.js:5:16)
at Module._compile (module.js:460:26)
at Object.Module._extensions..js (module.js:478:10)
at Module.load (module.js:355:32)
at Function.Module._load (module.js:310:12)
at Function.Module.runMain (module.js:501:10)
at startup (node.js:129:16)
at node.js:814:3`

I tried installing "json" locally and globally - the install seems to work but it makes no difference to the file error.

Answer 1

As Kevin B stated, you have to install body-parser locally and save it to the manifest:

npm install --save body-parser