BundleUtils.java

/*
 * Copyright 2008-2012 Alin Dreghiciu, Harald Wellmann.
 *
 * 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.swissbox.core;

import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;

import org.osgi.framework.Bundle;
import org.osgi.framework.BundleContext;

/**
 * Utilities related to bundles.
 *
 * @author Alin Dreghiciu
 * @author Harald Wellmann
 * @since 0.1.0, January 11, 2008
 */
public class BundleUtils
{

    /**
     * Discovers the bundle context for a bundle. If the bundle is an 4.1.0 or greater bundle it should have a method
     * that just returns the bundle context. Otherwise uses reflection to look for an internal bundle context.
     *
     * @param bundle the bundle from which the bundle context is needed
     *
     * @return corresponding bundle context or null if bundle context cannot be discovered
     */
    public static BundleContext getBundleContext( final Bundle bundle )
    {
        try
        {
            // first try to find the getBundleContext method (OSGi spec >= 4.10)
            final Method method = Bundle.class.getDeclaredMethod( "getBundleContext" );
            if( !method.isAccessible() )
            {
                method.setAccessible( true );
            }
            return (BundleContext) method.invoke( bundle );
        }
        catch( Exception e )
        {
            // then try to find a field in the bundle that looks like a bundle context
            try
            {
                final Field[] fields = bundle.getClass().getDeclaredFields();
                for( Field field : fields )
                {
                    if( BundleContext.class.isAssignableFrom( field.getType() ) )
                    {
                        if( !field.isAccessible() )
                        {
                            field.setAccessible( true );
                        }
                        return (BundleContext) field.get( bundle );
                    }
                }
            }
            catch( Exception ignore )
            {
                // ignore
            }
        }
        // well, discovery failed
        return null;
    }
    
    /**
     * Returns any bundle with the given symbolic name, or null if no such bundle exists. If there
     * are multiple bundles with the same symbolic name and different version, this method returns
     * the first bundle found.
     * 
     * @param bc bundle context
     * @param symbolicName bundle symbolic name
     * @param version bundle version
     * @return matching bundle, or null
     */
    public static Bundle getBundle( BundleContext bc, String symbolicName )
    {
        return getBundle( bc, symbolicName, null );
    }

    /**
     * Returns a list of all bundles with the given symbolic name.
     * 
     * @param bc bundle context
     * @param symbolicName bundle symbolic name
     * @return matching bundles. The list may be empty, but never null.
     */
    public static List<Bundle> getBundles( BundleContext bc, String symbolicName )
    {
        List<Bundle> bundles = new ArrayList<Bundle>();
        for( Bundle bundle : bc.getBundles() )
        {
            if( bundle.getSymbolicName().equals( symbolicName ) )
            {
                bundles.add( bundle );
            }
        }
        return bundles;
    }

    /**
     * Returns the bundle with the given symbolic name and the given version, or null if no such
     * bundle exists
     * 
     * @param bc bundle context
     * @param symbolicName bundle symbolic name
     * @param version bundle version
     * @return matching bundle, or null
     */
    public static Bundle getBundle( BundleContext bc, String symbolicName, String version )
    {
        for( Bundle bundle : bc.getBundles() )
        {
            if( bundle.getSymbolicName().equals( symbolicName ) )
            {
                if( version == null || version.equals( bundle.getVersion() ) )
                {
                    return bundle;
                }
            }
        }
        return null;
    }
}