Version Checker

This essay is about a suggested student project in Java programming. This essay gives a rough overview of how it might work. It does not describe an actual complete program. I have no source, object, specifications, file layouts or anything else useful to implementing this project. Everything I have to say to help you with this project is written below. I am not prepared to help you implement it; I have too many other projects of my own.

I do contract work for a living, which could include writing a program such as this. However, I don’t do people’s homework for them. That just robs them of an education.

You have my full permission to implement this project any way you please.

The Problem

Every program has a different way to find out that a new version has been released.

Some automatically install a new version.
Some send you an email.
Some notify you when you run the program.
Some check for updates when you click a menu item.
Some you must visit the vendor’s website.
Some you must probe the PAD file.

Unfortunately there is no standard way to check. Further it is very common for updates to go unnoticed or to get lost. Further, many manufacturers will notify you of micro updates, but not of major ones, or of ones for which there is a charge.

The Plan

What we need is a uniform, quick, automated way of discovering if any of your software is out of date. It works like this. You maintain an SQL database on a webserver that contains the following information about each product.

Product name
Current version
Information on how to get the new version, e.g. URL, some menu item to click etc.
Cost of the new version.

For each customer you maintain the following information:

Customer id
salted password
Customer name
Customer email
List of the software he has installed.
List of the versions of the software he has installed.
List of the latest versions of the software he has installed.

The customer then daily runs a little program that does a lookup by ID, and sends him a list of his products that are not current. If the customer does not check in for a few days, you send him an email with that information in human readable form. You could also provide a web interface where the customer must provide an ID and password.

This leaves the question, where does the information for the product versions come from. Here are some possibilities.

You probe the PAD file. PAD files are standard XML. It is already an established standard format for describing programs. This is easy and automatic.
Talk vendors into supplying PAD files.
You ask vendors to send you notification, perhaps in some standard format, perhaps a severely stripped down PAD file.
You do it manually, checking a list of websites.
You run copies of the software, and check with them periodically what is current.
You screen scrape with little custom bits of HTTP-GET code on the vendor’s websites to get the version info. Unfortunately, you must write custom code for each product.
You invent a computer and human-friendly screen-scrape format text file send it to vendors to put on their websites, and ask them to keep in current, e.g. a bit of XML. Publish the format and hope it catches on.

Commercial Considerations

The overhead on your server is almost nothing. This means you can service a very large number of clients with just a desktop computer. The customer does a single tiny record update and gets back a single tiny binary record. The process of propagating the knowledge of a new version to all customers that use it can happen in the background as a batch process.

You could finance the plan with Google Adsense ads, or with a small yearly fee.

Alternate Implementation

This is a much simpler approach to the same problem. You write a Java Web Start application. It has no central database. Every user is responsible for configuring his own apps. It displays a JTable with 6 columns:

Vercheck screenshot

The first column is a status indicator using icons.
The second column is the name of the application.
the third column is the current version number.
The fourth column is the URL of a webpage that can be used to test if the version has changed.
The fifth marker column is a string that exists somewhere on a webpage if the version has not changed. It would usually be the version, but it could be date, or some text in a revision. This string can alternatively be a Java regex to search for on the page. It might be necessary to add other criteria such the header date on a file, or the existence of some file.
The sixth column displays the date the version last changed.

Icons Used in VerCheck to Describe Applications
Icon	Meaning
	empty row
	invalid, e.g. bad date, bad/missing URL
	status not yet determined
	In the process of contacting and checking this website
	Could not contact website, or possibly the page is missing. Could indicate a version change.
	Unchanged, released over a year ago
	Unchanged, released in last year
	Unchanged, released in last month
	Unchanged, released in last week
	Version has recently changed. A new version is available. The marker is out of date.

Icons Used on VerCheck Command Buttons
Icon	Meaning
	add application at the spot selected
	remove selected application
	Check all websites for new versions

This program is primarily an exercise in using JTables. The user can fill in the app name, url and marker, add, delete, revise, sort etc. Then the user hits a button labelled check for new versions. The program then uses an HTTP GET to fetch each page and search it for the string. The program must persist the data between runs, perhaps using the preferences tools or perhaps the new bundled Derby SQL database.

I have written a version of this simpler version I call VerCheck. I use it to maintain the utilities page.

HTTP
Java Web Start
JTable
preferences
regex
SQL
URL

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