src/main/java/org/apache/servicemix/id/IdGenerator.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.servicemix.id;

/*
 * Copied from
 * http://svn.apache.org/repos/asf/incubator/activemq/trunk/activemq-core/src/main/java/org/apache/activemq/util/IdGenerator.java
 */

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.net.InetAddress;
import java.net.ServerSocket;

/**
 * Generator for Globally unique Strings.
 */

public class IdGenerator {

    private static final Logger LOG = LoggerFactory.getLogger(IdGenerator.class);

    private static final String UNIQUE_STUB;

    private static int instanceCount;

    private static String hostName;

    private String seed;

    private long sequence;

    public IdGenerator() {
        this("ID:");
    }

    /**
     * Construct an IdGenerator
     * 
     */
    public IdGenerator(String prefix) {
        synchronized (UNIQUE_STUB) {
            this.seed = prefix + UNIQUE_STUB + (instanceCount++) + ":";
        }
    }
    
    static {
        String stub = "";
        boolean canAccessSystemProps = true;
        try {
            SecurityManager sm = System.getSecurityManager();
            if (sm != null) {
                sm.checkPropertiesAccess();
            }
        } catch (SecurityException se) {
            canAccessSystemProps = false;
        }

        if (canAccessSystemProps) {
            try {
                hostName = InetAddress.getLocalHost().getHostAddress();
                ServerSocket ss = new ServerSocket(0);
                stub = hostName + "-" + Long.toHexString(ss.getLocalPort() ^ System.currentTimeMillis()) + "-";
                Thread.sleep(100);
                ss.close();
            } catch (Exception ioe) {
                LOG.warn("Could not generate unique stub", ioe);
            }
        } else {
            hostName = "localhost";
            stub = hostName + Long.toHexString(System.currentTimeMillis()) + "-";
        }
        UNIQUE_STUB = stub;
    }

    /**
     * As we have to find the hostname as a side-affect of generating a unique
     * stub, we allow it's easy retrevial here
     * 
     * @return the local host name
     */

    public static String getHostName() {
        return hostName;
    }

    /**
     * Generate a unqiue id
     * 
     * @return a unique id
     */

    public synchronized String generateId() {
        return this.seed + (this.sequence++);
    }

    /**
     * Generate a unique ID - that is friendly for a URL or file system
     * 
     * @return a unique id
     */
    public String generateSanitizedId() {
        String result = generateId();
        result = result.replace(':', '-');
        result = result.replace('_', '-');
        result = result.replace('.', '-');
        return result;
    }

}