Free Report: Do You Really Get Classloaders?

A [frightful] journey into the heart of Java ClassLoaders

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Do You Really Get Classloaders?

Why you should know, and fear, Classloaders

Classloaders are at the core of the Java language. Java EE containers, OSGi, various web frameworks and other tools use classloaders heavily. Yet, something goes wrong with classloading, would you know how to solve it?

Join us for a tour of the Java classloading mechanism, both from the JVM and developer point-of-view. We will look at typical problems related to classloading and how to solve them. NoClassDefFoundError, LinkageError and many others are symptoms of specific things going wrong that you can usually find and fix. For each problem, we'll go through an example with a corresponding solution. We'll also take a look at how and why classloaders leak and how can that be remedied.

And for dessert, we review how to reload a Java class using a dynamic classloader. To get there we'll see how objects, classes and classloaders are tied to each other and the process required to make changes. We begin with a bird’s eye view of the problem, explain the reloading process, and then proceed to a specific example to illustrate typical problems and solutions.