--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/share/classes/java/lang/instrument/ClassFileTransformer.java Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,188 @@
+/*
+ * Copyright 2003-2006 Sun Microsystems, Inc. All Rights Reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation. Sun designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Sun in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ */
+
+package java.lang.instrument;
+
+import java.security.ProtectionDomain;
+
+/*
+ * Copyright 2003 Wily Technology, Inc.
+ */
+
+/**
+ * An agent provides an implementation of this interface in order
+ * to transform class files.
+ * The transformation occurs before the class is defined by the JVM.
+ * <P>
+ * Note the term <i>class file</i> is used as defined in the chapter
+ * <a href="http://java.sun.com/docs/books/vmspec/2nd-edition/html/ClassFile.doc.html#80959">The class File Format</a>
+ * of <i>The Java Virtual Machine Specification</i>, to mean a sequence
+ * of bytes in class file format, whether or not they reside in a file.
+ *
+ * @see java.lang.instrument.Instrumentation
+ * @see java.lang.instrument.Instrumentation#addTransformer
+ * @see java.lang.instrument.Instrumentation#removeTransformer
+ * @since 1.5
+ */
+
+public interface ClassFileTransformer {
+ /**
+ * The implementation of this method may transform the supplied class file and
+ * return a new replacement class file.
+ *
+ * <P>
+ * There are two kinds of transformers, determined by the <code>canRetransform</code>
+ * parameter of
+ * {@link java.lang.instrument.Instrumentation#addTransformer(ClassFileTransformer,boolean)}:
+ * <ul>
+ * <li><i>retransformation capable</i> transformers that were added with
+ * <code>canRetransform</code> as true
+ * </li>
+ * <li><i>retransformation incapable</i> transformers that were added with
+ * <code>canRetransform</code> as false or where added with
+ * {@link java.lang.instrument.Instrumentation#addTransformer(ClassFileTransformer)}
+ * </li>
+ * </ul>
+ *
+ * <P>
+ * Once a transformer has been registered with
+ * {@link java.lang.instrument.Instrumentation#addTransformer(ClassFileTransformer,boolean)
+ * addTransformer},
+ * the transformer will be called for every new class definition and every class redefinition.
+ * Retransformation capable transformers will also be called on every class retransformation.
+ * The request for a new class definition is made with
+ * {@link java.lang.ClassLoader#defineClass ClassLoader.defineClass}
+ * or its native equivalents.
+ * The request for a class redefinition is made with
+ * {@link java.lang.instrument.Instrumentation#redefineClasses Instrumentation.redefineClasses}
+ * or its native equivalents.
+ * The request for a class retransformation is made with
+ * {@link java.lang.instrument.Instrumentation#retransformClasses Instrumentation.retransformClasses}
+ * or its native equivalents.
+ * The transformer is called during the processing of the request, before the class file bytes
+ * have been verified or applied.
+ * When there are multiple transformers, transformations are composed by chaining the
+ * <code>transform</code> calls.
+ * That is, the byte array returned by one call to <code>transform</code> becomes the input
+ * (via the <code>classfileBuffer</code> parameter) to the next call.
+ *
+ * <P>
+ * Transformations are applied in the following order:
+ * <ul>
+ * <li>Retransformation incapable transformers
+ * </li>
+ * <li>Retransformation incapable native transformers
+ * </li>
+ * <li>Retransformation capable transformers
+ * </li>
+ * <li>Retransformation capable native transformers
+ * </li>
+ * </ul>
+ *
+ * <P>
+ * For retransformations, the retransformation incapable transformers are not
+ * called, instead the result of the previous transformation is reused.
+ * In all other cases, this method is called.
+ * Within each of these groupings, transformers are called in the order registered.
+ * Native transformers are provided by the <code>ClassFileLoadHook</code> event
+ * in the Java Virtual Machine Tool Interface).
+ *
+ * <P>
+ * The input (via the <code>classfileBuffer</code> parameter) to the first
+ * transformer is:
+ * <ul>
+ * <li>for new class definition,
+ * the bytes passed to <code>ClassLoader.defineClass</code>
+ * </li>
+ * <li>for class redefinition,
+ * <code>definitions.getDefinitionClassFile()</code> where
+ * <code>definitions</code> is the parameter to
+ * {@link java.lang.instrument.Instrumentation#redefineClasses
+ * Instrumentation.redefineClasses}
+ * </li>
+ * <li>for class retransformation,
+ * the bytes passed to the new class definition or, if redefined,
+ * the last redefinition, with all transformations made by retransformation
+ * incapable transformers reapplied automatically and unaltered;
+ * for details see
+ * {@link java.lang.instrument.Instrumentation#retransformClasses
+ * Instrumentation.retransformClasses}
+ * </li>
+ * </ul>
+ *
+ * <P>
+ * If the implementing method determines that no transformations are needed,
+ * it should return <code>null</code>.
+ * Otherwise, it should create a new <code>byte[]</code> array,
+ * copy the input <code>classfileBuffer</code> into it,
+ * along with all desired transformations, and return the new array.
+ * The input <code>classfileBuffer</code> must not be modified.
+ *
+ * <P>
+ * In the retransform and redefine cases,
+ * the transformer must support the redefinition semantics:
+ * if a class that the transformer changed during initial definition is later
+ * retransformed or redefined, the
+ * transformer must insure that the second class output class file is a legal
+ * redefinition of the first output class file.
+ *
+ * <P>
+ * If the transformer throws an exception (which it doesn't catch),
+ * subsequent transformers will still be called and the load, redefine
+ * or retransform will still be attempted.
+ * Thus, throwing an exception has the same effect as returning <code>null</code>.
+ * To prevent unexpected behavior when unchecked exceptions are generated
+ * in transformer code, a transformer can catch <code>Throwable</code>.
+ * If the transformer believes the <code>classFileBuffer</code> does not
+ * represent a validly formatted class file, it should throw
+ * an <code>IllegalClassFormatException</code>;
+ * while this has the same effect as returning null. it facilitates the
+ * logging or debugging of format corruptions.
+ *
+ * @param loader the defining loader of the class to be transformed,
+ * may be <code>null</code> if the bootstrap loader
+ * @param className the name of the class in the internal form of fully
+ * qualified class and interface names as defined in
+ * <i>The Java Virtual Machine Specification</i>.
+ * For example, <code>"java/util/List"</code>.
+ * @param classBeingRedefined if this is triggered by a redefine or retransform,
+ * the class being redefined or retransformed;
+ * if this is a class load, <code>null</code>
+ * @param protectionDomain the protection domain of the class being defined or redefined
+ * @param classfileBuffer the input byte buffer in class file format - must not be modified
+ *
+ * @throws IllegalClassFormatException if the input does not represent a well-formed class file
+ * @return a well-formed class file buffer (the result of the transform),
+ or <code>null</code> if no transform is performed.
+ * @see Instrumentation#redefineClasses
+ */
+ byte[]
+ transform( ClassLoader loader,
+ String className,
+ Class<?> classBeingRedefined,
+ ProtectionDomain protectionDomain,
+ byte[] classfileBuffer)
+ throws IllegalClassFormatException;
+}