Archive for February, 2011

SvnBot 1.1 Released

Friday, February 25th, 2011

The SvnBot is a simple single purpose IRC robot that monitors one or more SVN repositories. When changes are committed to a source repository the robot makes an announcement in an IRC channel. The purpose of the tool is to allow a team of developers to keep up to date on changes that other team members are making. Here at TDL we have a geographically distributed team of software developers some in Austin and Lubbock along with my self in College Station. This is one tool that helps the team keep in sync with each other.

There are already many tools available that do this task [1][2][3], however they all require the use of SVN commit-hooks. Commit-hooks are run on the repository’s server allowing external tools to be notified when specific events occur. Using commit-hooks can work reasonably well if you have access to the server’s configuration, but that is not always the case. Instead of relying on commit-hooks; the SvnBot runs independently, periodically polling the repository for any updates. When an update in found a message will be announced in IRC.

Below is an example IRC message. The message includes the author and their commit message along with some brief statistics about the number of files affected and a URL. If multiple files were affected by a single commit then the url reported is to the common path, i.e. the closest directory that contains all the affected files.

Scott: “SAND-30, reviewed the pom file: removing unneeded dependencies, declaring output to be UTF-8 and added a few comments.(Rev 666: 1 file modified)

Special thanks to the Texas Digital Library, my employer, for allowing me to release this as an open source project.

Mixed XML and Property files?

Tuesday, February 1st, 2011

Have you ever wanted the simplicity of a plain old Java properties file but with just a little bit of grouping provided by XML? I’ve been working on a small side-project recently and it requires a simple configuration file of a dozen items or so. The project needed a repeatable set of configuration parameters, so that it could connect to several SVN servers. Each connection needed a URL, username, password, and a few other ancillary properties. This is a pain to do in a plain old properties file. You have to do something with the naming of the properties to relate them together, such as:

property.1.url = http://...
property.1.username = Bob
property.1.password = Bob’s secret

property.2.url = http://...
property.2.username = Joe
property.2.password = Joe’s secret  

This way works but it’s sort of annoying and can be confusing for someone else to understand what’s going on. They would likely need to read the documentation, especially if it’s more complex with multiple types of repeating parameters. There are several alternatives, you could try encoding all the parameters into one property but that’s even harder for a user to figure out. A slightly better alternative is to use something hierarchical like XML, thus:

		<password>Bob’s secret</password>
		<password>Joe’s secret</password>

This is easier to understand, but it’s very verbose. Each property is labeled twice, once to open the tag and again to close the tag. XML is good for complex things like HTML or specific file formats with a dedicated reader. However, XML is not great for humans to read, let alone edit quickly.

A better solution, combine both!

Instead of either XML or properties file we can munge the two together to create something that is easier for users to manage. = value1
property.two = value2

	url = http://...
	username = Bob
	password = Bob’s secret

	url = http://...
	username = Joe
	password = Joe’s secret

The combined format is similar to Apache’s httpd configuration format where name/value pairs are also mixed with nestable elements. It’s very close to the simplicity of a plain old properties file, but has just enough expressivity to handle grouping of elements. It’s a win-win.