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The Pax Logging API Library is to allow for the Pax Logging Service to be reloaded without stopping the many dependent bundles. It also contains the OSGi Log Service API and the Knopflerfish Log API.

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/*
 * Copyright 2010 Guillaume Nodet.
 *
 * 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.ops4j.pax.logging.internal;

import java.lang.reflect.Method;

import org.osgi.framework.Bundle;
import org.osgi.framework.FrameworkUtil;

public final class BundleHelper
{
    private BundleHelper()
    {
    }

    private static final SecurityManagerEx securityManager;
    private static final Method getBundleMethod;

    static
    {
        securityManager = new SecurityManagerEx();
        Method mth = null;
        try
        {
            mth = FrameworkUtil.class.getMethod("getBundle", new Class[] { Class.class });
        }
        catch (NoSuchMethodException e)
        {
        }
        getBundleMethod = mth;
    }

    public static Bundle getCallerBundle(Bundle defaultBundle)
    {
        if (getBundleMethod == null) {
            return defaultBundle;
        }

        try
        {
            Class[] classCtx = securityManager.getClassContext();
            /* Skip first 2 classes on call stack since:
             *  classCtx[0] is always SecurityManagerEx.getClassContext()
             *  classCtx[1] is always BundleHelper.getCallerBundle()
             */
            Bundle curBundle = null;
            for (int i = 2; i < classCtx.length; i++)
            {
                Bundle bundle = FrameworkUtil.getBundle(classCtx[i]);
                if (bundle == null)
                {
                    return defaultBundle;
                }
                else if (curBundle == null)
                {
                    curBundle = bundle;
                }
                else if (bundle != curBundle)
                {
                    return bundle;
                }
            }
        }
        catch (Exception e)
        {
        }
        
        return defaultBundle;
    }

    static class SecurityManagerEx extends SecurityManager
    {
        public Class[] getClassContext()
        {
            return super.getClassContext();
        }
    }

}