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Introduction to bytekin

What is bytekin?

bytekin is a lightweight, easy-to-use Java bytecode transformation framework built on top of ASM. It allows developers to programmatically modify Java classes at the bytecode level, enabling powerful code injection, method interception, and transformation capabilities.

bytekin is designed to be:

  • Simple: Intuitive annotation-based API
  • Lightweight: Minimal dependencies (only ASM)
  • Flexible: Multiple transformation strategies
  • Powerful: Support for complex bytecode manipulations

Key Features

  • Inject: Insert custom code at specific points in methods (head, return, etc.)
  • Invoke: Intercept method calls and modify their behavior
  • Redirect: Change method call targets
  • Constant Modification: Modify constant values in bytecode
  • Variable Modification: Manipulate local variables
  • Mapping Support: Transform class and method names automatically
  • Builder Pattern: Fluent API for constructing transformers

Use Cases

bytekin is ideal for scenarios where you need to:

  1. Add logging or monitoring to existing classes without modifying source code
  2. Implement AOP (Aspect-Oriented Programming) without framework overhead
  3. Add security checks at runtime
  4. Modify third-party library behavior at the bytecode level
  5. Implement mocking or stubbing for testing
  6. Instrument code for profiling or analytics
  7. Apply cross-cutting concerns to multiple classes

Why bytekin?

Unlike full-featured frameworks, bytekin is:

  • Minimal: Only depends on ASM, no heavy dependencies
  • Direct: Works with bytecode directly without reflection overhead
  • Flexible: Supports both annotation-based and programmatic approaches
  • Fast: Efficient bytecode manipulation at JVM load time

Project Structure

The bytekin project is organized into several modules:

  • Transformation Engine: Core bytecode manipulation logic
  • Injection System: Method injection capabilities
  • Mapping System: Class and method name mapping support
  • Utilities: Helper classes for bytecode manipulation

Next Steps