Byte Buddy is a code generation and manipulation library for the Java virtual machine that creates and modifies Java classes at runtime without requiring a compiler.
The tool solves the problem of needing to generate or transform Java classes dynamically during application execution. Unlike the proxy utilities built into the Java Class Library, which are limited to implementing interfaces, Byte Buddy allows creation of arbitrary classes with full control over their structure and behavior. It provides a high-level API designed to be accessible without deep knowledge of Java bytecode or the class file format, while remaining fully customizable for those who need to work at the bytecode level. The library can be used to modify classes manually, through a Java agent, or during a build process.
Byte Buddy suits projects that need runtime code generation for tasks like creating dynamic proxies beyond interface implementation, bytecode instrumentation, or generating classes on demand. The tool is particularly valuable when you need to avoid adding dependencies to generated classes, since Byte Buddy leaves no trace in the bytecode it produces and generated classes can exist without the library on the classpath. It maintains broad Java version compatibility, supporting class file generation for any Java version while running on older JVMs, with a single lightweight dependency on the ASM bytecode parser library.
The project actively maintains compatibility with new Java versions through support of the Class File API, automatically extending support to newly released versions unless previously unknown class file features emerge. Development follows a structured approach to version management, with distinct release lines for different Java class file versions to ensure users can select appropriate versions for their target platforms.
