From ‘Class Not Found’ to Calm: Practical Shading and Shadowing for Java Apps

Tue, 07 Jul 2026 07:07:12 +0000

Your pipeline is green, the app is deployed, and everything looks fine… until production says “nope”. A request fails and the logs show ClassNotFoundException, or worse, NoSuchMethodError. These are among the most confusing runtime errors because the code compiled successfully, but the JVM is acting differently than you would expect.

Let’s dive in and explore how the class loader works, what class shadowing is (when one class silently wins over another on the classpath) and what class shading is (when you deliberately relocate packages so multiple versions can coexist). We’ll also see how these two concepts can help solve mysterious production issues and make your app more stable and secure.

Kamil Banach on JAVAPRO International

From ‘Class Not Found’ to Calm: Practical Shading and Shadowing for Java Apps