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Provides a small and fast bytecode manipulation framework.
The ASM framework is organized
around the {@link jersey.repackaged.org.objectweb.asm.ClassVisitor ClassVisitor},
{@link jersey.repackaged.org.objectweb.asm.FieldVisitor FieldVisitor} and
{@link jersey.repackaged.org.objectweb.asm.MethodVisitor MethodVisitor} interfaces, which allow
one to visit the fields and methods of a class, including the bytecode
instructions of each method.
In addition to these main interfaces, ASM provides a {@link
jersey.repackaged.org.objectweb.asm.ClassReader ClassReader} class, that can parse an
existing class and make a given visitor visit it. ASM also provides
a {@link jersey.repackaged.org.objectweb.asm.ClassWriter ClassWriter} class, which is
a visitor that generates Java class files.
In order to generate a class from scratch, only the {@link
jersey.repackaged.org.objectweb.asm.ClassWriter ClassWriter} class is necessary. Indeed,
in order to generate a class, one must just call its visitXXX
methods with the appropriate arguments to generate the desired fields
and methods. See the "helloworld" example in the ASM distribution for
more details about class generation.
In order to modify existing classes, one must use a {@link
jersey.repackaged.org.objectweb.asm.ClassReader ClassReader} class to analyze
the original class, a class modifier, and a {@link jersey.repackaged.org.objectweb.asm.ClassWriter
ClassWriter} to construct the modified class. The class modifier
is just a {@link jersey.repackaged.org.objectweb.asm.ClassVisitor ClassVisitor}
that delegates most of the work to another {@link jersey.repackaged.org.objectweb.asm.ClassVisitor
ClassVisitor}, but that sometimes changes some parameter values,
or call additional methods, in order to implement the desired
modification process. In order to make it easier to implement such
class modifiers, ASM provides the {@link jersey.repackaged.org.objectweb.asm.ClassAdapter
ClassAdapter} and {@link jersey.repackaged.org.objectweb.asm.MethodAdapter MethodAdapter}
classes, which implement the {@link jersey.repackaged.org.objectweb.asm.ClassVisitor ClassVisitor}
and {@link jersey.repackaged.org.objectweb.asm.MethodVisitor MethodVisitor} interfaces by
delegating all work to other visitors. See the "adapt" example in the ASM
distribution for more details about class modification.
The size of the core ASM library, asm.jar, is only 42KB, which is much
smaller than the size of the
BCEL library (504KB), and than the
size of the
SERP library (150KB). ASM is also
much faster than these tools. Indeed the overhead of a load time class
transformation process is of the order of 60% with ASM, 700% or more with BCEL,
and 1100% or more with SERP (see the test/perf directory in the ASM
distribution)!
@since ASM 1.3