1 <html> 2 <!-- 3 * ASM: a very small and fast Java bytecode manipulation framework 4 * Copyright (c) 2000-2005 INRIA, France Telecom 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the copyright holders nor the names of its 16 * contributors may be used to endorse or promote products derived from 17 * this software without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 20 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 23 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF 29 * THE POSSIBILITY OF SUCH DAMAGE. 30 --> 31 <body> 32 Provides a small and fast bytecode manipulation framework. 33 34 <p> 35 The <a href="http://www.objectweb.org/asm">ASM</a> framework is organized 36 around the {@link org.objectweb.asm.ClassVisitor ClassVisitor}, 37 {@link org.objectweb.asm.FieldVisitor FieldVisitor} and 38 {@link org.objectweb.asm.MethodVisitor MethodVisitor} interfaces, which allow 39 one to visit the fields and methods of a class, including the bytecode 40 instructions of each method. 41 42 <p> 43 In addition to these main interfaces, ASM provides a {@link 44 org.objectweb.asm.ClassReader ClassReader} class, that can parse an 45 existing class and make a given visitor visit it. ASM also provides 46 a {@link org.objectweb.asm.ClassWriter ClassWriter} class, which is 47 a visitor that generates Java class files. 48 49 <p> 50 In order to generate a class from scratch, only the {@link 51 org.objectweb.asm.ClassWriter ClassWriter} class is necessary. Indeed, 52 in order to generate a class, one must just call its visit<i>XXX</i> 53 methods with the appropriate arguments to generate the desired fields 54 and methods. See the "helloworld" example in the ASM distribution for 55 more details about class generation. 56 57 <p> 58 In order to modify existing classes, one must use a {@link 59 org.objectweb.asm.ClassReader ClassReader} class to analyze 60 the original class, a class modifier, and a {@link org.objectweb.asm.ClassWriter 61 ClassWriter} to construct the modified class. The class modifier 62 is just a {@link org.objectweb.asm.ClassVisitor ClassVisitor} 63 that delegates most of the work to another {@link org.objectweb.asm.ClassVisitor 64 ClassVisitor}, but that sometimes changes some parameter values, 65 or call additional methods, in order to implement the desired 66 modification process. In order to make it easier to implement such 67 class modifiers, ASM provides the {@link org.objectweb.asm.ClassAdapter 68 ClassAdapter} and {@link org.objectweb.asm.MethodAdapter MethodAdapter} 69 classes, which implement the {@link org.objectweb.asm.ClassVisitor ClassVisitor} 70 and {@link org.objectweb.asm.MethodVisitor MethodVisitor} interfaces by 71 delegating all work to other visitors. See the "adapt" example in the ASM 72 distribution for more details about class modification. 73 74 <p> 75 The size of the core ASM library, <tt>asm.jar</tt>, is only 42KB, which is much 76 smaller than the size of the 77 <a href="http://jakarta.apache.org/bcel">BCEL</a> library (504KB), and than the 78 size of the 79 <a href="http://serp.sourceforge.net">SERP</a> library (150KB). ASM is also 80 much faster than these tools. Indeed the overhead of a load time class 81 transformation process is of the order of 60% with ASM, 700% or more with BCEL, 82 and 1100% or more with SERP (see the <tt>test/perf</tt> directory in the ASM 83 distribution)! 84 85 @since ASM 1.3 86 </body> 87 </html> 88
