Hibernate example source code file (JavassistClassTransformer.java)

This example Hibernate source code file (JavassistClassTransformer.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Hibernate tags/keywords

bytearrayoutputstream, bytearrayoutputstream, classfile, classfile, classloader, coremessagelogger, datainputstream, dataoutputstream, fieldtransformer, fieldtransformer, io, ioexception, javassistclasstransformer, security, string, string

The Hibernate JavassistClassTransformer.java source code

/*
 * Hibernate, Relational Persistence for Idiomatic Java
 *
 * Copyright (c) 2008-2011, Red Hat Inc. or third-party contributors as
 * indicated by the @author tags or express copyright attribution
 * statements applied by the authors.  All third-party contributions are
 * distributed under license by Red Hat Inc.
 *
 * This copyrighted material is made available to anyone wishing to use, modify,
 * copy, or redistribute it subject to the terms and conditions of the GNU
 * Lesser General Public License, as published by the Free Software Foundation.
 *
 * This program 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 Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this distribution; if not, write to:
 * Free Software Foundation, Inc.
 * 51 Franklin Street, Fifth Floor
 * Boston, MA  02110-1301  USA
 */
package org.hibernate.bytecode.internal.javassist;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.security.ProtectionDomain;

import javassist.bytecode.ClassFile;
import org.jboss.logging.Logger;

import org.hibernate.HibernateException;
import org.hibernate.internal.CoreMessageLogger;
import org.hibernate.bytecode.buildtime.spi.ClassFilter;
import org.hibernate.bytecode.spi.AbstractClassTransformerImpl;

/**
 * Enhance the classes allowing them to implements InterceptFieldEnabled
 * This interface is then used by Hibernate for some optimizations.
 *
 * @author Emmanuel Bernard
 * @author Steve Ebersole
 */
public class JavassistClassTransformer extends AbstractClassTransformerImpl {

    private static final CoreMessageLogger LOG = Logger.getMessageLogger(CoreMessageLogger.class,
                                                                       JavassistClassTransformer.class.getName());

	public JavassistClassTransformer(ClassFilter classFilter, org.hibernate.bytecode.buildtime.spi.FieldFilter fieldFilter) {
		super( classFilter, fieldFilter );
	}

	@Override
    protected byte[] doTransform(
			ClassLoader loader,
			String className,
			Class classBeingRedefined,
			ProtectionDomain protectionDomain,
			byte[] classfileBuffer) {
		ClassFile classfile;
		try {
			// WARNING: classfile only
			classfile = new ClassFile( new DataInputStream( new ByteArrayInputStream( classfileBuffer ) ) );
		}
		catch (IOException e) {
            LOG.unableToBuildEnhancementMetamodel(className);
			return classfileBuffer;
		}
		FieldTransformer transformer = getFieldTransformer( classfile );
		if ( transformer != null ) {
            LOG.debugf("Enhancing %s", className);
			DataOutputStream out = null;
			try {
				transformer.transform( classfile );
				ByteArrayOutputStream byteStream = new ByteArrayOutputStream();
				out = new DataOutputStream( byteStream );
				classfile.write( out );
				return byteStream.toByteArray();
			}
			catch (Exception e) {
                LOG.unableToTransformClass(e.getMessage());
				throw new HibernateException( "Unable to transform class: " + e.getMessage() );
			}
			finally {
				try {
					if ( out != null ) out.close();
				}
				catch (IOException e) {
					//swallow
				}
			}
		}
		return classfileBuffer;
	}

	protected FieldTransformer getFieldTransformer(final ClassFile classfile) {
		if ( alreadyInstrumented( classfile ) ) {
			return null;
		}
		return new FieldTransformer(
				new FieldFilter() {
					public boolean handleRead(String desc, String name) {
						return fieldFilter.shouldInstrumentField( classfile.getName(), name );
					}

					public boolean handleWrite(String desc, String name) {
						return fieldFilter.shouldInstrumentField( classfile.getName(), name );
					}

					public boolean handleReadAccess(String fieldOwnerClassName, String fieldName) {
						return fieldFilter.shouldTransformFieldAccess( classfile.getName(), fieldOwnerClassName, fieldName );
					}

					public boolean handleWriteAccess(String fieldOwnerClassName, String fieldName) {
						return fieldFilter.shouldTransformFieldAccess( classfile.getName(), fieldOwnerClassName, fieldName );
					}
				}
		);
	}

	private boolean alreadyInstrumented(ClassFile classfile) {
		String[] intfs = classfile.getInterfaces();
		for ( int i = 0; i < intfs.length; i++ ) {
			if ( FieldHandled.class.getName().equals( intfs[i] ) ) {
				return true;
			}
		}
		return false;
	}
}