Validating Objects Through Metadata (3 tags)
Metadata, in the form of J2SE 5.0's annotation, allow you to mark up your your code with declarative information, and then use reflection to pull out those annotations at runtime and use them. Jacob Hookom shows how these techniques can be used to validate input to your application.
User-Friendly Form Validation with PHP and CSS (3 tags)
Any non-trivial web application processes form data, and every secure web application has to validate that data on the server. Balancing security with user-friendliness can be tricky. Jeff Cogswell demonstrates one approach.
Constraining Validation (2 tags)
What's the difference between validation and business rules? XML developers discuss how and why to use them.