//Import express, used by node.js to setup rest endpoints
var express = require('express');
//Import AWS, used to interact with Amazon Web Services including S3 storage
var aws = require('aws-sdk');
//Extra tools that should be included in request handlers
var extend = require('util')._extend;
var defaultConfig = require('./config.json');

/**
 * Dynamic Request Handler
 */

function DynUiHandler() {
    var s3Bucket, s3;
    //Setup config options
    var config = {};
    extend(config, defaultConfig);
    //Grab information for S3 from config.json
    s3Workspace = config.S3Root;
    s3Bucket = config.S3Bucket;

    // Setup S3
    s3 = new aws.S3(config);


    /**
     * List files in the s3 bucket.
     * @param {object} req - The Express request object.
     * @param {object} res - The Express response object.
     */
    function listS3Data(req, res) {
    //Take the parameter passed from the REST call and set that as the bucket to be accessed in the call to s3.
        var params = {
            Bucket: req.params.bucket
        }; 
        //Call the S3 package's built in listObjects function to return what is avaiable in the specified bucket

        s3.listObjects(params, function(err, data) {
        //check if error occured and if so, halt and report it to client.
            if (err) {
                var code = err.code || 500;
                var message = err.message || err;
                res.status(code).send({
                    error: message
                });
            } 
            // If no error, push every object found in the response with a '.dat' extension to an array that will be returned to client 
            else {
                var files = [];
                //Look at each file contained in data returned by s3.listObjects()
                data.Contents.forEach(function(file) {
                    //Searches for files with .dat in the bucket requested
                    if(file.Key.endsWith('.dat')){
                        //If found, store that file information in the files array.
                        files.push(file);
                    }
                });
            }
            //send the files array containing metadata of all .dat files found.
            res.send(files);
        });
    };

    //Initialize request handler, run when GSF starts up.
    this.init = function(app) {
        // Set up request handler to host the html subdirectory as a webpage.
        app.use('/dynui/', require('express').static(__dirname + '/html/'));
        // Set up a rest call that runs listS3Data and supplies the accomponying bucket parameter.
        app.get('/s3data/:bucket', listS3Data);
    };
}
//
module.exports = DynUiHandler;

After restarting the server I was able to hit my rest endpoint by pasting the following in my browser:
http://localhost:9191/s3data/mybucket

This would return me JSON of the contents of “mybucket”

 
Using this information I was able to give a user of my application real time information right inside of the interface about which data they have available to them. 
 

This is a simple example of how I customized a stock request handler to make my web demo more powerful. However, the ability to modify the source code of such a powerful system in a modular fashion provides a safe way to mold GSF into the exact form and shape you need to fit into your own architecture. 

It might just be me but I much prefer that over restructuring my own existing architecture to fit closed source code I know nothing about.