94 lines
4.6 KiB
HTML
94 lines
4.6 KiB
HTML
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<html>
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<!--
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* ASM: a very small and fast Java bytecode manipulation framework
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* Copyright (c) 2000,2002,2003 INRIA, France Telecom
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the copyright holders nor the names of its
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* contributors may be used to endorse or promote products derived from
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* this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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* LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
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* THE POSSIBILITY OF SUCH DAMAGE.
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*
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* Contact: Eric.Bruneton@rd.francetelecom.com
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*
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* Author: Eric Bruneton
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-->
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<body>
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Provides a small and fast bytecode manipulation framework.
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<p>
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The <a href="http://www.objectweb.org/asm">ASM</a> framework is organized
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around the {@link org.objectweb.asm.ClassVisitor ClassVisitor} and {@link
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org.objectweb.asm.CodeVisitor CodeVisitor} interfaces, which allows one to
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visit the fields and methods of a class, including the bytecode instructions of
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each method.
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<p>
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In addition to these two main interfaces, ASM provides a {@link
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org.objectweb.asm.ClassReader ClassReader} class, that can parse an
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existing class and make a given visitor visit it. ASM also provides
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a {@link org.objectweb.asm.ClassWriter ClassWriter} class, which is
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a visitor that generates Java class files.
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<p>
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In order to generate a class from scratch, only the {@link
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org.objectweb.asm.ClassWriter ClassWriter} class is necessary. Indeed,
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in order to generate a class, one must just call its visit<i>XXX</i>
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methods with the appropriate arguments to generate the desired fields
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and methods. See the "helloworld" example in the ASM distribution for
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more details about class generation.
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<p>
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In order to modify existing classes, one must use a {@link
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org.objectweb.asm.ClassReader ClassReader} class to analyse
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the original class, a class modifier, and a {@link org.objectweb.asm.ClassWriter
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ClassWriter} to construct the modified class. The class modifier
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is just a {@link org.objectweb.asm.ClassVisitor ClassVisitor}
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that delegates most of the work to another {@link org.objectweb.asm.ClassVisitor
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ClassVisitor}, but that sometimes changes some parameter values,
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or call additional methods, in order to implement the desired
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modification process. In order to make it easier to implement such
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class modifiers, ASM provides the {@link org.objectweb.asm.ClassAdapter
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ClassAdapter} and {@link org.objectweb.asm.CodeAdapter CodeAdapter}
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classes, which implement the {@link org.objectweb.asm.ClassVisitor ClassVisitor} and
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{@link org.objectweb.asm.CodeVisitor CodeVisitor} interfaces by delegating
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all work to other visitors. See the "adapt" example in the ASM distribution
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for more details about class modification.
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<p>
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The size of the core ASM library, <tt>asm.jar</tt>, is only 25KB, which is much
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more smaller than
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the size of the <a href="http://jakarta.apache.org/bcel">BCEL</a> library (350KB
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without the class verifier), and than the size of the
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<a href="http://serp.sourceforge.net">SERP</a> library (150KB). ASM is also
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much more faster than these tools. Indeed the overhead of a load time class
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transformation process is of the order of 60% with ASM, 700% or more with BCEL,
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and 1100% or more with SERP (see the <tt>test/perf</tt> directory in the ASM
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distribution)! kASM is a subset of ASM, for class generation only (it includes
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the {@link org.objectweb.asm.ClassWriter ClassWriter}, but not the {@link
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org.objectweb.asm.ClassReader ClassReader}). The size of this library,
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<tt>kasm.jar</tt>, is only 16KB.
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@since ASM 1.3
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</body>
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</html>
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