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ActiveMQ example source code file (IdGenerator.java)
The ActiveMQ IdGenerator.java source code/** * 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.activemq.util; import java.net.ServerSocket; import java.util.concurrent.atomic.AtomicLong; import org.slf4j.Logger; import org.slf4j.LoggerFactory; /** * 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 AtomicLong sequence = new AtomicLong(1); private int length; 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 = InetAddressUtil.getLocalHostName(); ServerSocket ss = new ServerSocket(0); stub = "-" + ss.getLocalPort() + "-" + System.currentTimeMillis() + "-"; Thread.sleep(100); ss.close(); } catch (Exception ioe) { LOG.warn("could not generate unique stub", ioe); } } else { hostName = "localhost"; stub = "-1-" + System.currentTimeMillis() + "-"; } UNIQUE_STUB = stub; } /** * Construct an IdGenerator */ public IdGenerator(String prefix) { synchronized (UNIQUE_STUB) { this.seed = prefix + UNIQUE_STUB + (instanceCount++) + ":"; this.length = this.seed.length() + ("" + Long.MAX_VALUE).length(); } } public IdGenerator() { this("ID:" + hostName); } /** * 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() { StringBuilder sb = new StringBuilder(length); sb.append(seed); sb.append(sequence.getAndIncrement()); return sb.toString(); } /** * 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; } /** * From a generated id - return the seed (i.e. minus the count) * * @param id the generated identifer * @return the seed */ public static String getSeedFromId(String id) { String result = id; if (id != null) { int index = id.lastIndexOf(':'); if (index > 0 && (index + 1) < id.length()) { result = id.substring(0, index + 1); } } return result; } /** * From a generated id - return the generator count * * @param id * @return the count */ public static long getSequenceFromId(String id) { long result = -1; if (id != null) { int index = id.lastIndexOf(':'); if (index > 0 && (index + 1) < id.length()) { String numStr = id.substring(index + 1, id.length()); result = Long.parseLong(numStr); } } return result; } /** * Does a proper compare on the ids * * @param id1 * @param id2 * @return 0 if equal else a positive if id1 is > id2 ... */ public static int compare(String id1, String id2) { int result = -1; String seed1 = IdGenerator.getSeedFromId(id1); String seed2 = IdGenerator.getSeedFromId(id2); if (seed1 != null && seed2 != null) { result = seed1.compareTo(seed2); if (result == 0) { long count1 = IdGenerator.getSequenceFromId(id1); long count2 = IdGenerator.getSequenceFromId(id2); result = (int)(count1 - count2); } } return result; } } Other ActiveMQ examples (source code examples)Here is a short list of links related to this ActiveMQ IdGenerator.java source code file: |
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