ServiceHelper.java

/*
 * Copyright © 2015 Yale University and others.  All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
 * and is available at http://www.eclipse.org/legal/epl-v10.html
 */
package org.opendaylight.alto.basic.endpointcostservice.helper;

import org.osgi.framework.BundleContext;
import org.osgi.framework.FrameworkUtil;
import org.osgi.framework.ServiceReference;
import org.osgi.framework.ServiceRegistration;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.Dictionary;

public class ServiceHelper {
    private static final Logger logger = LoggerFactory
            .getLogger(ServiceHelper.class);

    /**
     * Register a Global Service in the OSGi service registry
     *
     * @param clazz
     *          The target class
     * @param instance
     *          of the object exporting the service, be careful the object must
     *          implement/extend clazz else the registration will fail unless a
     *          ServiceFactory is passed as parameter
     * @param properties
     *          The properties to be attached to the service registration
     * @return the ServiceRegistration if registration happened, null otherwise
     */
    public static ServiceRegistration registerGlobalServiceWReg(Class<?> clazz,
                                                                Object instance, Dictionary<String, Object> properties) {
        try {
            BundleContext bCtx = FrameworkUtil.getBundle(instance.getClass())
                    .getBundleContext();
            if (bCtx == null) {
                logger.error("Could not retrieve the BundleContext");
                return null;
            }

            ServiceRegistration registration = bCtx.registerService(clazz.getName(),
                    instance, properties);
            return registration;
        } catch (Exception e) {
            logger.error("Exception {} while registering the service {}",
                    e.getMessage(), instance.toString());
        }
        return null;
    }

    /**
     * Retrieve global instance of a class via OSGI registry, if there are many
     * only the first is returned.
     *
     * @param clazz
     *          The target class
     * @param bundle
     *          The caller
     */
    public static Object getGlobalInstance(Class<?> clazz, Object bundle) {
        return getGlobalInstance(clazz, bundle, null);
    }


    /**
     * Retrieve global instance of a class via OSGI registry, if there are many
     * only the first is returned. On this version an LDAP type of filter is
     * applied
     *
     * @param clazz
     *          The target class
     * @param bundle
     *          The caller
     * @param serviceFilter
     *          LDAP filter to be applied in the search
     */
    public static Object getGlobalInstance(Class<?> clazz, Object bundle,
                                           String serviceFilter) {
        Object[] instances = getGlobalInstances(clazz, bundle, serviceFilter);
        if (instances != null) {
            return instances[0];
        }
        return null;
    }

    /**
     * Retrieve all the Instances of a Service, optionally filtered via
     * serviceFilter if non-null else all the results are returned if null
     *
     * @param clazz
     *          The target class
     * @param bundle
     *          The caller
     * @param serviceFilter
     *          LDAP filter to be applied in the search
     */
    @SuppressWarnings("unchecked")
    public static Object[] getGlobalInstances(Class<?> clazz, Object bundle,
                                              String serviceFilter) {
        Object instances[] = null;
        try {
            BundleContext bCtx = FrameworkUtil.getBundle(bundle.getClass())
                    .getBundleContext();

            ServiceReference[] services = bCtx.getServiceReferences(clazz.getName(),
                    serviceFilter);

            if (services != null) {
                instances = new Object[services.length];
                for (int i = 0; i < services.length; i++) {
                    instances[i] = bCtx.getService(services[i]);
                }
            }
        } catch (Exception e) {
            logger.error("Instance reference is NULL");
        }
        return instances;
    }
}