Don't Let Your Bytecode Just Sit There

Java bytecode just works. It works so well that the JVM has over 250 languages that compile to bytecode. It works so well that we can usually ignore it.

But given Java bytecode's success and ubiquity, shouldn't we crack the hood and see how it works? Once you do, you may discover that bytecode manipulation is not only fun, it can be used to solve interesting problems.

In this session, we will take a look at how bytecode is represented and how to use the ASM library to view and manipulate it. We'll use the Java Instrumentation API to modify classes as they're loaded and change their behavior.