Rahul Sharma (Editor)

ObjectWeb ASM

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Developer(s)
  
OW2 Consortium

Operating system
  
Cross-platform

Written in
  
Java

Stable release
  
5.2 / December 23, 2016 (2016-12-23)

Preview release
  
6.0 Alpha / June 19, 2016 (2016-06-19)

Type
  
bytecode Engineering Library

The ASM library is a project of the OW2 Consortium. It provides a simple API for decomposing, modifying, and recomposing binary Java classes (i.e. bytecode). The project was originally conceived and developed by Eric Bruneton. ASM is Java-centric at present, and does not currently have a backend that exposes other bytecode implementations (such as .NET bytecode, Python bytecode, etc.).

Contents

The ASM name does not mean anything: it is just a reference to the asm keyword of C, which allows some functions to be implemented in assembly language.

Uses

ASM provides a simple library that exposes the internal aggregate components of a given Java class through its visitor oriented API. ASM also provides, on top of this visitor API, a tree API that represents classes as object constructs. Both APIs can be used for modifying the binary bytecode, as well as generating new bytecode (via injection of new code into the existing code, or through generation of new classes altogether.) The ASM library has been used in several diverse applications, such as:

  • Performance and Profiling
    • Instrumentation calls that capture performance metrics can be injected into Java class binaries to examine memory/coverage data. (For example, injecting instrumentation at entry/exit points.)
  • Implementation of New Language Semantics
    • For example, Groovy uses ASM to generate its bytecode. Also, Aspect-Oriented additions to the Java language have been implemented by using ASM to decompose class structures for point-cut identification, and then again when reconstituting the class by injecting aspect-related code back into the binary. (See: AspectWerkz)

    Invokedynamic

    Since version 3.2, ASM has added support for the new invokedynamic code, which allows method invocation relying on dynamic type checking on the latest JDK 7 binaries, thus easing support for dynamically typed languages.

    References

    ObjectWeb ASM Wikipedia
    (Text) CC BY-SA