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
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 (normal ...
). 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
The .NET platform (pronounced as "''dot net"'') is a free and open-source, managed code, managed computer software framework for Microsoft Windows, Windows, Linux, and macOS operating systems. The project is mainly developed by Microsoft emplo ...
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 interve ...
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
''Groovy'' (or, less commonly, ''groovie'' or ''groovey'') is a slang colloquialism popular during the 1960s and 1970s. It is roughly synonymous with words such as "excellent", "fashionable", or "amazing", depending on context.
History
The word ...
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'' (for example, integer, floating point, string) to every '' term'' (a word, phrase, or other set of symbols). Usu ...
on the latest
JDK 7 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
*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 (programming language) libraries
Software using the BSD license