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| * ASM: a very small and fast Java bytecode manipulation framework |
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| <body> |
| Provides a small and fast bytecode manipulation framework. |
| |
| <p> |
| The <a href="http://www.objectweb.org/asm">ASM</a> framework is organized |
| around the {@link org.objectweb.asm.ClassVisitor ClassVisitor}, |
| {@link org.objectweb.asm.FieldVisitor FieldVisitor}, |
| {@link org.objectweb.asm.MethodVisitor MethodVisitor} and |
| {@link org.objectweb.asm.AnnotationVisitor AnnotationVisitor} abstract classes, |
| which allow one to visit the fields, methods and annotations of a class, |
| including the bytecode instructions of each method. |
| |
| <p> |
| In addition to these main abstract classes, ASM provides a {@link |
| org.objectweb.asm.ClassReader ClassReader} class, that can parse an |
| existing class and make a given visitor visit it. ASM also provides |
| a {@link org.objectweb.asm.ClassWriter ClassWriter} class, which is |
| a visitor that generates Java class files. |
| |
| <p> |
| In order to generate a class from scratch, only the {@link |
| org.objectweb.asm.ClassWriter ClassWriter} class is necessary. Indeed, |
| in order to generate a class, one must just call its visit<i>Xxx</i> |
| 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. |
| |
| <p> |
| In order to modify existing classes, one must use a {@link |
| org.objectweb.asm.ClassReader ClassReader} class to analyze |
| the original class, a class modifier, and a {@link org.objectweb.asm.ClassWriter |
| ClassWriter} to construct the modified class. The class modifier |
| is just a {@link org.objectweb.asm.ClassVisitor ClassVisitor} |
| that delegates most of the work to another {@link 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, the {@link org.objectweb.asm.ClassVisitor |
| ClassVisitor} and {@link org.objectweb.asm.MethodVisitor MethodVisitor} |
| classes delegate by default all the method calls they receive to an |
| optional visitor. See the "adapt" example in the ASM |
| distribution for more details about class modification. |
| |
| <p> |
| The size of the core ASM library, <tt>asm.jar</tt>, is only 45KB, which is much |
| smaller than the size of the |
| <a href="http://jakarta.apache.org/bcel">BCEL</a> library (504KB), and than the |
| size of the |
| <a href="http://serp.sourceforge.net">SERP</a> 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 <tt>test/perf</tt> directory in the ASM |
| distribution)! |
| |
| @since ASM 1.3 |
| </body> |
| </html> |
