Jiapi is a tool which can be used to alter the normal class loading behavior. Instead of letting the class to be loaded as it is, Jiapi is used to manipulate classes' bytecode. The manipulated class is then passed to a class loader which loads it into a Java virtual machine. In addition to just described just-in-time bytecode weaving, Jiapi can be used to instrument a class ahead-of-time. In this mode compiled classes are preprocessed by Jiapi instrumentors and modified classes are then serialized on a filesystem to be executed later.

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