NodeJS + Express + Mongoose（MongoDB）数据库插入错误

// Launch express and server
var express = require(\'express\');
var app = express.createServer();

//connect to DB
var mongoose = require(\'mongoose\');
var db = mongoose.connect(\'mongodb://127.0.0.1/napkin_0.1\');

// Define Model
var Schema = mongoose.Schema;

var UserSchema = new Schema({
    name : String,
    age : String
});

mongoose.model(\'Document\', UserSchema);
var User = mongoose.model(\'Document\');

var user = new User();

user.name = \'Jim\';
user.age = \'27\';
user.save(function(err, user_Saved){
    if(err){
        throw err;
        console.log(err);
    }else{
        console.log(\'saved!\');
    }
});

//Launch Server
app.listen(3002);