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The Apache Commons Codec package contains simple encoder and decoders for various formats such as Base64 and Hexadecimal. In addition to these widely used encoders and decoders, the codec package also maintains a collection of phonetic encoding utilities.

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/*   Copyright 2004 The Apache Software Foundation
 *
 *   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 org.apache.xmlbeans.impl.common;

import java.lang.ref.SoftReference;
import java.util.ArrayList;

import org.apache.xmlbeans.SchemaTypeLoader;
import org.apache.xmlbeans.SystemProperties;

/**
 * This class encapsulates the caching strategy for XmlBeans.
 * By subclassing this, a client of XmlBeans can implement caches that are
 * more suitable for different applications using information that XmlBeans
 * cannot know.
 * 
 * This class works as a singleton and as a default implementation for the cache.
 * You can set a particular implementation using the "xmlbean.systemcacheimpl"
 * system property or using the static {@link set} method.
 * Subclasses of this need to be thread-safe. An implementation can be replaced
 * at any time, so use of static variables is discouraged to ensure proper cleanup.
 */
public class SystemCache
{
    private static SystemCache INSTANCE = new SystemCache();

    static
    {
        String cacheClass = SystemProperties.getProperty("xmlbean.systemcacheimpl");
        Object impl = null;
        if (cacheClass != null)
        {
            try
            {
                impl = Class.forName(cacheClass).newInstance();
                if (!(impl instanceof SystemCache))
                throw new ClassCastException("Value for system property " +
                    "\"xmlbean.systemcacheimpl\" points to a class (" + cacheClass +
                    ") which does not derive from SystemCache");
            }
            catch (ClassNotFoundException cnfe)
            {
                throw new RuntimeException("Cache class " + cacheClass +
                    " specified by \"xmlbean.systemcacheimpl\" was not found.",
                    cnfe);
            }
            catch (InstantiationException ie)
            {
                throw new RuntimeException("Could not instantiate class " +
                    cacheClass + " as specified by \"xmlbean.systemcacheimpl\"." +
                    " An empty constructor may be missing.", ie);
            }
            catch (IllegalAccessException iae)
            {
                throw new RuntimeException("Could not instantiate class " +
                    cacheClass + " as specified by \"xmlbean.systemcacheimpl\"." +
                    " A public empty constructor may be missing.", iae);
            }
        }
        if (impl != null)
            INSTANCE = (SystemCache) impl;
    }

    public static synchronized final void set(SystemCache instance)
    {
        INSTANCE = instance;
    }

    public static final SystemCache get()
    {
        return INSTANCE;
    }

    public SchemaTypeLoader getFromTypeLoaderCache(ClassLoader cl)
    {
        return null;
    }

    public void addToTypeLoaderCache(SchemaTypeLoader stl, ClassLoader cl)
    {
        return;
    }

    private ThreadLocal tl_saxLoaders = new ThreadLocal();

    public void clearThreadLocals() {
        tl_saxLoaders.remove();
    }

    public Object getSaxLoader()
    {
        SoftReference s = (SoftReference) tl_saxLoaders.get();
        if (s == null)
            return null;
        else
            return s.get();
    }

    public void setSaxLoader(Object saxLoader)
    {
        tl_saxLoaders.set(new SoftReference(saxLoader));
    }
}