The ASM library is a project of the
OW2
OW2 is an independent non-profit international consortium dedicated to developing open-source software code infrastructure for middleware information systems. OW2 federates IT vendors and users, universities, and research centers from Europe, A ...
consortium. It provides a simple API for decomposing, modifying, and recomposing binary Java classes (i.e.
bytecode
Bytecode (also called portable code or p-code) is a form of instruction set designed for efficient execution by a software interpreter. Unlike human-readable source code, bytecodes are compact numeric codes, constants, and references (norma ...
). 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.).
The name "ASM" is not an acronym: 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
A visitor, in English and Welsh law and history, is an overseer of an autonomous ecclesiastical or eleemosynary institution, often a charitable institution set up for the perpetual distribution of the founder's alms and bounty, who can inter ...
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
In computer programming, a type system is a logical system comprising a set of rules that assigns a property called a type to every "term" (a word, phrase, or other set of symbols). Usually the terms are various constructs of a computer progra ...
on the latest
JDK 7
The Java language has undergone several changes since JDK 1.0 as well as numerous additions of classes and packages to the standard library. Since J2SE 1.4, the evolution of the Java language has been governed by the Java Community ...
binaries, thus easing support for
dynamically typed languages.
Release history
This table presents only releases with significant steps in ObjectWeb ASM history, aside from versions that mainly fixed bugs and improved performance.
See also
*
Byte Code Engineering Library
The Byte Code Engineering Library (BCEL) is a project sponsored by the Apache Foundation previously under their Jakarta Project, Jakarta charter to provide a simple API for decomposing, modifying, and recomposing binary Java (programming language) ...
*
Javassist
References
External links
*{{official website
OW2 Home- The OW2 Consortium Home Page.
AspectWerkz- The AspectWerkz Project Home Page. (One of the high-visibility projects that makes use of ASM.)
OW2
Java APIs
Java (programming language) libraries
Software using the BSD license