# RMIRegistryController.java

    /**
     *  Licensed to the Apache Software Foundation (ASF) under one
     *  or more contributor license agreements.  See the NOTICE file
     *  distributed with this work for additional information
     *  regarding copyright ownership.  The ASF licenses this file
     *  to you 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.apache.synapse.commons.util;

    import org.apache.commons.logging.Log;
    import org.apache.commons.logging.LogFactory;
    import org.apache.synapse.commons.SynapseCommonsException;

    import java.rmi.NoSuchObjectException;
    import java.rmi.RemoteException;
    import java.rmi.registry.LocateRegistry;
    import java.rmi.registry.Registry;
    import java.rmi.server.UnicastRemoteObject;
    import java.util.ArrayList;
    import java.util.Collection;
    import java.util.HashMap;
    import java.util.Map;

    /**
     * Creates and manages RMI registries
     */
    public class RMIRegistryController {

        public static final Log log = LogFactory.getLog(RMIRegistryController.class);

        private static RMIRegistryController ourInstance = new RMIRegistryController();
        private final Map<String, Registry> registriesCache = new HashMap<String, Registry>();

        public static RMIRegistryController getInstance() {
            return ourInstance;
        }

        private RMIRegistryController() {
        }

        /**
         * Creates a RMI local registry with given port
         *
         * @param port The port of the RMI registry to be created
         */
        public void createLocalRegistry(int port) {

            try {

                String key = toKey(port);

                synchronized (registriesCache) {
                    if (registriesCache.containsKey(key)) {
                        if (log.isDebugEnabled()) {
                            log.debug("There is an RMI registry bound to given port :" + port);
                        }
                        return;
                    }

                    Registry locateRegistry = LocateRegistry.createRegistry(port);
                    if (locateRegistry == null) {
                        handleException("Unable to create a RMI registry with port : " + port);
                    }

                    registriesCache.put(key, locateRegistry);
                }

            } catch (RemoteException e) {
                String msg = "Couldn't create a local registry(RMI) : port " + port +
                        " already in use.";
                handleException(msg, e);
            }
        }

        /**
         * removes if there is a RMI local registry instance
         *
         * @param port The port of the RMI registry to be removed
         */
        public void removeLocalRegistry(int port) {

            String key = toKey(port);
            synchronized (registriesCache) {
                if (registriesCache.containsKey(key)) {
                    removeRegistry(key, registriesCache.get(key));
                } else {
                    if (log.isDebugEnabled()) {
                        log.debug("There is no RMi registry for port : " + port);
                    }
                }
            }
        }

        /**
         * Removes all registered RMI registries
         */
        public void shutDown() {

            synchronized (registriesCache) {
                Collection<String> registryKeys = new ArrayList<String>(registriesCache.size());
                registryKeys.addAll(registriesCache.keySet());
                for (String key : registryKeys) {
                    removeRegistry(key, registriesCache.get(key));
                }
            }
        }

        /**
         * Helper method to remove a RMI registry instance
         *
         * @param key      The port of the RMI registry to be removed
         * @param registry Registry instance
         */
        private void removeRegistry(String key, Registry registry) {

            if (registry != null) {
                synchronized (registriesCache) {
                    try {
                        log.info("Removing the RMI registry bound to port : " + key);
                        UnicastRemoteObject.unexportObject(registry, true);
                        registriesCache.remove(key);
                    } catch (NoSuchObjectException e) {
                        String msg = "Error when stopping local registry(RMI)";
                        handleException(msg, e);
                    }
                }

            }

        }

        private static String toKey(int port) {

            assertPositive(port);
            return String.valueOf(port);
        }

        private static void assertPositive(int port) {

            if (port < 0) {
                handleException("Invalid port number : " + port);
            }
        }

        /**
         * Helper methods for handle errors.
         *
         * @param msg The error message
         * @param e   The exception
         */
        private static void handleException(String msg, Exception e) {
            log.error(msg, e);
            throw new SynapseCommonsException(msg, e);
        }

        /**
         * Helper methods for handle errors.
         *
         * @param msg The error message
         */
        private static void handleException(String msg) {
            log.error(msg);
            throw new SynapseCommonsException(msg);
        }

    }