com.gfactor.jpa.core.MyClassFileTransformerAdapter.java Source code

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Here is the source code for com.gfactor.jpa.core.MyClassFileTransformerAdapter.java

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/*
 * Copyright 2002-2006 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.gfactor.jpa.core;

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

import javax.persistence.spi.ClassTransformer;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import org.springframework.util.Assert;

/**
 * Simple adapter that implements the <code>java.lang.instrument.ClassFileTransformer</code>
 * interface based on a JPA ClassTransformer which a JPA PersistenceProvider asks the
 * PersistenceUnitInfo to install in the current runtime.
 *
 * @author Rod Johnson
 * @since 2.0
 * @see javax.persistence.spi.PersistenceUnitInfo#addTransformer(javax.persistence.spi.ClassTransformer)
 */
class MyClassFileTransformerAdapter implements ClassFileTransformer {

    private static final Log logger = LogFactory.getLog(MyClassFileTransformerAdapter.class);

    private final ClassTransformer classTransformer;

    public MyClassFileTransformerAdapter(ClassTransformer classTransformer) {
        Assert.notNull(classTransformer, "ClassTransformer must not be null");
        this.classTransformer = classTransformer;
    }

    public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined,
            ProtectionDomain protectionDomain, byte[] classfileBuffer) {

        try {
            byte[] transformed = this.classTransformer.transform(loader, className, classBeingRedefined,
                    protectionDomain, classfileBuffer);
            if (transformed != null && logger.isDebugEnabled()) {
                logger.debug("Transformer of class [" + this.classTransformer.getClass().getName()
                        + "] transformed class [" + className + "]; bytes in=" + classfileBuffer.length
                        + "; bytes out=" + transformed.length);
            }
            return transformed;
        } catch (ClassCircularityError ex) {
            logger.error("Error weaving class [" + className + "] with " + "transformer of class ["
                    + this.classTransformer.getClass().getName() + "]", ex);
            throw new IllegalStateException("Could not weave class [" + className + "]", ex);
        } catch (Throwable ex) {
            if (logger.isWarnEnabled()) {
                logger.warn("Error weaving class [" + className + "] with " + "transformer of class ["
                        + this.classTransformer.getClass().getName() + "]", ex);
            }
            // The exception will be ignored by the class loader, anyway...
            throw new IllegalStateException("Could not weave class [" + className + "]", ex);
        }
    }

    @Override
    public String toString() {
        return "Standard ClassFileTransformer wrapping JPA transformer: " + this.classTransformer;
    }

}