org.ow2.petals.log.handler.SourceHelpers Maven / Gradle / Ivy

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/**
 * Copyright (c) 2015-2016 Linagora
 * 
 * This program/library is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 2.1 of the License, or (at your
 * option) any later version.
 * 
 * This program/library 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 program/library; If not, see http://www.gnu.org/licenses/
 * for the GNU Lesser General Public License version 2.1.
 */
package org.ow2.petals.log.handler;

import java.io.File;
import java.io.FileWriter;
import java.util.logging.Handler;

import javax.xml.transform.Source;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.stream.StreamResult;

import org.apache.commons.pool.BasePoolableObjectFactory;
import org.apache.commons.pool.ObjectPool;
import org.apache.commons.pool.impl.GenericObjectPool;

/**
 * 
 * Homemade version of easycommons-utils SourceHelper.
 * 
 * Needed because we don't want easycommons-utils and its transformer pool arriving in the system classloader.
 * 
 * This class should be used only by {@link PetalsPayloadDumperFileHandler}, so its visibility and methods' visibilities
 * are restricted to package scope.
 * 
 * @author vnoel
 *
 */
class SourceHelpers {

    private final ObjectPool transformers;

    /**
     * 
     * @param maxActive
     *            maximum number of instances
     * @param maxIdle
     *            maximum number of idle instances
     */
    public SourceHelpers(final int maxActive, final int maxIdle) {
        this.transformers = new GenericObjectPool<>(new TransformersFactory(), maxActive,
                GenericObjectPool.DEFAULT_WHEN_EXHAUSTED_ACTION, GenericObjectPool.DEFAULT_MAX_WAIT, maxIdle);
    }

    public void toFile(final Source source, final File fileToWrite) throws Exception {
        final Transformer transformer = transformers.borrowObject();
        try (final FileWriter writer = new FileWriter(fileToWrite)) {
            transformer.transform(source, new StreamResult(writer));
            writer.write("\n");
        } finally {
            transformers.returnObject(transformer);
        }
    }

    private static class TransformersFactory extends BasePoolableObjectFactory {

        /**
         * this should be instantiated only once with the logging {@link Handler} that use {@link SourceHelpers} and
         * thus using its classloader to choose the {@link TransformerFactory}.
         */
        private final TransformerFactory factory = TransformerFactory.newInstance();

        @Override
        public Transformer makeObject() throws Exception {
            return factory.newTransformer();
        }

    }

}