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Hibernate developmental JSR 317 (Java Persistence API 2.0) contracts. Used to allow incremental implementation of features on the way to full JPA 2.0 support.

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// $Id: ClassTransformer.java 16130 2009-03-10 14:28:07Z hardy.ferentschik $
// EJB3 Specification Copyright 2004-2009 Sun Microsystems, Inc.
package javax.persistence.spi;

import java.lang.instrument.IllegalClassFormatException;
import java.security.ProtectionDomain;

/**
 * A persistence provider supplies an instance of this
 * interface to the PersistenceUnitInfo.addTransformer
 * method. The supplied transformer instance will get
 * called to transform entity class files when they are
 * loaded or redefined. The transformation occurs before
 * the class is defined by the JVM.
 */
public interface ClassTransformer {
	/**
	 * Invoked when a class is being loaded or redefined.
	 * The implementation of this method may transform the
	 * supplied class file and return a new replacement class
	 * file.
	 *
	 * @param loader The defining loader of the class to be
	 * transformed, may be null if the bootstrap loader
	 * @param className The name of the class in the internal form
	 * of fully qualified class and interface names
	 * @param classBeingRedefined If this is a redefine, the
	 * class being redefined, otherwise null
	 * @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
	 *
	 * @return A well-formed class file buffer (the result of
	 *         the transform), or null if no transform is performed
	 *
	 * @throws IllegalClassFormatException If the input does
	 *                                     not represent a well-formed class file
	 */
	byte[] transform(ClassLoader loader,
					 String className,
					 Class classBeingRedefined,
					 ProtectionDomain protectionDomain,
					 byte[] classfileBuffer)
			throws IllegalClassFormatException;
}