Friday, April 22, 2011

Properties file troubles

I stumbled over a stupid properties file gotcha the other day trying to get a Spring META-INF/spring.schemas file working. Spring uses this file to translate an XML Schema schemaLocation into the name of a classpath resource. This allows Spring to load the schema directly from the classpath instead of downloading it from a remote server which might not be reachable from your deployment environment (e.g. because of firewalls). So for instance, suppose you have the following in your XML:
<beans xmlns=""
If you combine this with the following META-INF/spring.schemas file, Spring will load demo.xsd directly from the classpath without even trying to access
The key thing to notice in the properties file is the escaping backslash before the colon! This is necessary because a colon is a valid delimiter in a Java properties file:
public static void main(String[] args) throws IOException {
 StringReader propsIn = new StringReader("");
 Properties props = new Properties();

 for (String propName : props.stringPropertyNames()) {
  System.out.println(propName + " --> " + props.getProperty(propName));
  // prints: http --> //
Keep in mind that all colons need to be escaped! So don't forget the colon in front of the port number:

Thursday, April 7, 2011

Software and Mud

There seems to be a strange relationship between software and mud. Many will be familiar with the Big Ball of Mud architectural style and there are countless examples of code that resembles mud more than anything else.

A while ago a colleague of mine used an analogy between a software related problem he was facing and wading through mud (or as we say in Dutch: "door de moose ploegen"). I'm amazed at how poignant this analogy actually is. Think of a situation where the first thing you notice is that you have mud on the soles of your shoes. As you trot on you quickly end up knee deep in mud. At this point you can either back out and retreat to solid ground, or persevere, in which case you often end up stuck!

Of course you might also make it through, as John Carmack once noted:
Yes, you can make windows do anything you want to if you have enough time to beat on it, but you can come out of it feeling like you just walked through a sewer. [.plan]

Many software related situations come to mind that closely follow this story:
  • Merging exercises gone wrong
  • Refactoring plans that start simple but spiral out of control
  • Anything to do with character encoding
  • ...
Feel free to add this mud analogy to your software vocabulary!

(As an aside: some people can wade through mud more elegantly than others, as Kate Moss illustrates.)