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DataNucleus Core provides the primary components of a heterogenous Java persistence solution. It supports persistence API's being layered on top of the core functionality.

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/**********************************************************************
Copyright (c) 2006 Erik Bengtson and others. All rights reserved.
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.
 

Contributors:
    ...
**********************************************************************/
package org.datanucleus.plugin;

import org.datanucleus.ClassConstants;
import org.datanucleus.ClassLoaderResolver;
import org.datanucleus.util.NucleusLogger;
import org.datanucleus.util.Localiser;

/**
 * Factory for PluginRegistry. 
 * Creates an instance of PluginRegistry based on the available PluginRegistry implementation in the classpath.
 */
public class PluginRegistryFactory
{
    /**
     * Instantiates a PluginRegistry. Will typically use NonManagedPluginRegistry in non-OSGi environments and
     * OSGiPluginRegistry otherwise, subject to user input.
     * @param registryClassName Name of the registry
     * @param registryBundleCheck What to do on check of bundles (Only for Non-OSGi)
     * @param allowUserBundles Whether to only load DataNucleus bundles (org.datanucleus) (Only for Non-OSGi)
     * @param clr the ClassLoaderResolver
     * @return instance of the PluginRegistry
     */
    public static PluginRegistry newPluginRegistry(String registryClassName, String registryBundleCheck, boolean allowUserBundles, ClassLoaderResolver clr)
    {
        PluginRegistry registry = null;
        if (registryClassName != null)
        {
            // Try the user-specified registry
            registry = newInstance(registryClassName, registryClassName, clr);
            if (registry != null)
            {
                if (NucleusLogger.GENERAL.isDebugEnabled())
                {
                    NucleusLogger.GENERAL.debug("Using PluginRegistry " + registry.getClass().getName());
                }
                return registry;
            }
        }

        if (NucleusLogger.GENERAL.isDebugEnabled())
        {
            NucleusLogger.GENERAL.debug("Using PluginRegistry " + NonManagedPluginRegistry.class.getName());
        }
        return new NonManagedPluginRegistry(clr, registryBundleCheck, allowUserBundles);
    }

    /**
     * Instantiates a PluginRegistry. Only proceed if the testClass is found in the classpath
     * @param testClass A test class
     * @param registryClassName Name of the class that implements {@link PluginRegistry}
     * @return instance of the PluginRegistry
     */
    private static PluginRegistry newInstance(String testClass, String registryClassName, ClassLoaderResolver clr)
    {
        try
        {
            if (clr.classForName(testClass, org.datanucleus.ClassConstants.NUCLEUS_CONTEXT_LOADER) == null)
            {
                if (NucleusLogger.GENERAL.isDebugEnabled())
                {
                    NucleusLogger.GENERAL.debug(Localiser.msg("024005", registryClassName));
                }
            }
            return (PluginRegistry) clr.classForName(registryClassName, org.datanucleus.ClassConstants.NUCLEUS_CONTEXT_LOADER).getConstructor(
                new Class[] { ClassConstants.CLASS_LOADER_RESOLVER }).newInstance(new Object[] { clr });
        }
        catch (Exception e)
        {
            // Just ignore all exceptions
        }
        return null;
    }
}