org.apache.activemq.util.IdGenerator Maven / Gradle / Ivy
/**
* 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.io.IOException;
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 final AtomicLong sequence = new AtomicLong(1);
private int length;
public static final String PROPERTY_IDGENERATOR_HOSTNAME ="activemq.idgenerator.hostname";
public static final String PROPERTY_IDGENERATOR_LOCALPORT ="activemq.idgenerator.localport";
public static final String PROPERTY_IDGENERATOR_PORT ="activemq.idgenerator.port";
static {
String stub = "";
boolean canAccessSystemProps = true;
try {
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
sm.checkPropertiesAccess();
}
} catch (SecurityException se) {
canAccessSystemProps = false;
}
if (canAccessSystemProps) {
hostName = System.getProperty(PROPERTY_IDGENERATOR_HOSTNAME);
int localPort = Integer.parseInt(System.getProperty(PROPERTY_IDGENERATOR_LOCALPORT, "0"));
int idGeneratorPort = 0;
ServerSocket ss = null;
try {
if( hostName==null ) {
hostName = InetAddressUtil.getLocalHostName();
}
if( localPort==0 ) {
idGeneratorPort = Integer.parseInt(System.getProperty(PROPERTY_IDGENERATOR_PORT, "0"));
LOG.trace("Using port {}", idGeneratorPort);
ss = new ServerSocket(idGeneratorPort);
localPort = ss.getLocalPort();
stub = "-" + localPort + "-" + System.currentTimeMillis() + "-";
Thread.sleep(100);
} else {
stub = "-" + localPort + "-" + System.currentTimeMillis() + "-";
}
} catch (Exception e) {
if (LOG.isTraceEnabled()) {
LOG.trace("could not generate unique stub by using DNS and binding to local port", e);
} else {
LOG.warn("could not generate unique stub by using DNS and binding to local port: {} {}", e.getClass().getCanonicalName(), e.getMessage());
}
// Restore interrupted state so higher level code can deal with it.
if (e instanceof InterruptedException) {
Thread.currentThread().interrupt();
}
} finally {
if (ss != null) {
try {
// TODO: replace the following line with IOHelper.close(ss) when Java 6 support is dropped
ss.close();
} catch (IOException ioe) {
if (LOG.isTraceEnabled()) {
LOG.trace("Closing the server socket failed", ioe);
} else {
LOG.warn("Closing the server socket failed" + " due " + ioe.getMessage());
}
}
}
}
}
// fallback
if (hostName == null) {
hostName = "localhost";
}
hostName = sanitizeHostName(hostName);
if (stub.length() == 0) {
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 retrieval here
*
* @return the local host name
*/
public static String getHostName() {
return hostName;
}
/**
* Generate a unique id
*
* @return a unique id
*/
public synchronized String generateId() {
StringBuilder sb = new StringBuilder(length);
sb.append(seed);
sb.append(sequence.getAndIncrement());
return sb.toString();
}
public static String sanitizeHostName(String hostName) {
boolean changed = false;
StringBuilder sb = new StringBuilder();
for (char ch : hostName.toCharArray()) {
// only include ASCII chars
if (ch < 127) {
sb.append(ch);
} else {
changed = true;
}
}
if (changed) {
String newHost = sb.toString();
LOG.info("Sanitized hostname from: {} to: {}", hostName, newHost);
return newHost;
} else {
return hostName;
}
}
/**
* 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 identifier
* @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);
}
}
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;
}
}