org.wicketstuff.osgi.util.OsgiServiceLookup Maven / Gradle / Ivy

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/*
 * Copyright 2011 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.wicketstuff.osgi.util;

import java.util.Map;
import java.util.Map.Entry;

import org.apache.wicket.WicketRuntimeException;
import org.osgi.framework.BundleContext;
import org.osgi.framework.Filter;
import org.osgi.framework.FrameworkUtil;
import org.osgi.framework.InvalidSyntaxException;
import org.osgi.util.tracker.ServiceTracker;

/**
 * A utility class for looking up services from the OSGi registry. The methods of this class wait
 * for the service for a given timeout (default 10 seconds) and throw a
 * {@code WicketRuntimeException} when no matching service becomes available during this period.
 * 
 * NOTE: Prefixing some method calls with our own class name is a workaround for a bug in the Oracle
 * Java compiler, which does not occur when compiling in Eclipse.
 * 
 * @author Harald Wellmann
 * 
 */
public class OsgiServiceLookup
{

	public static final long DEFAULT_TIMEOUT = 10000;

	public static  T getOsgiService(BundleContext bc, String className)
	{
		return OsgiServiceLookup. getOsgiService(bc, className, DEFAULT_TIMEOUT, null);
	}

	public static  T getOsgiService(BundleContext bc, Class type)
	{
		return getOsgiService(bc, type, DEFAULT_TIMEOUT);
	}

	public static  T getOsgiService(BundleContext bc, Class type, Map props)
	{
		return getOsgiService(bc, type, DEFAULT_TIMEOUT, props);
	}

	/**
	 * Returns a service matching the given criteria.
	 * 
	 * @param 
	 *            class implemented or extended by the service
	 * @param bc
	 *            bundle context for accessing the OSGi registry
	 * @param type
	 *            class implemented or extended by the service
	 * @param timeout
	 *            maximum wait period in milliseconds
	 * @param props
	 *            properties to be matched by the service
	 * @return matching service (not null)
	 * @throws WicketRuntimeException
	 */
	public static  T getOsgiService(BundleContext bc, Class type, long timeout,
		Map props)
	{
		return OsgiServiceLookup. getOsgiService(bc, type.getName(), timeout, props);
	}

	public static  T getOsgiService(BundleContext bc, Class type, long timeout)
	{
		return OsgiServiceLookup. getOsgiService(bc, type.getName(), timeout, null);
	}

	@SuppressWarnings("unchecked")
	public static  T getOsgiService(BundleContext bc, String className, long timeout,
		Map props)
	{
		ServiceTracker tracker = createServiceTracker(bc, className, props);
		try
		{
			tracker.open();
			Object svc = tracker.waitForService(timeout);
			if (svc == null)
			{
				throw new WicketRuntimeException("gave up waiting for service " + className);
			}
			return (T)svc;
		}
		catch (InterruptedException exc)
		{
			throw new WicketRuntimeException(exc);
		}
		finally
		{
			tracker.close();
		}
	}


	private static ServiceTracker createServiceTracker(BundleContext bc, String className,
		Map props)
	{
		if (props == null || props.isEmpty())
		{
			return new ServiceTracker(bc, className, null);
		}

		StringBuilder builder = new StringBuilder("(&(objectClass=");
		builder.append(className);
		builder.append(')');
		for (Entry entry : props.entrySet())
		{
			builder.append('(');
			builder.append(entry.getKey());
			builder.append('=');
			builder.append(entry.getValue());
			builder.append(')');
		}
		builder.append(')');
		try
		{
			Filter filter;
			filter = FrameworkUtil.createFilter(builder.toString());
			ServiceTracker tracker = new ServiceTracker(bc, filter, null);
			return tracker;
		}
		catch (InvalidSyntaxException exc)
		{
			throw new WicketRuntimeException(exc);
		}
	}
}