Mega Code Archive
Generator for Globally unique Strings
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/**
* 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.
*/
import java.net.InetAddress;
import java.net.ServerSocket;
/**
* Generator for Globally unique Strings.
*/
public class UuidGenerator {
private static final String UNIQUE_STUB;
private static int instanceCount;
private static String hostName;
private String seed;
private long sequence;
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().getHostName();
ServerSocket ss = new ServerSocket(0);
stub = "/" + ss.getLocalPort() + "-" + System.currentTimeMillis() + "/";
Thread.sleep(100);
ss.close();
} catch (Exception ioe) {
System.out.println("Could not generate unique stub" + ioe);
}
} else {
hostName = "localhost";
stub = "-1-" + System.currentTimeMillis() + "-";
}
UNIQUE_STUB = generateSanitizedId(stub);
}
public UuidGenerator(String prefix) {
synchronized (UNIQUE_STUB) {
this.seed = generateSanitizedId(prefix + UNIQUE_STUB + (instanceCount++) + "-");
}
}
public UuidGenerator() {
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
*/
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() {
return generateSanitizedId(generateId());
}
/**
* Ensures that the id is friendly for a URL or file system
*
* @param id the unique id
* @return the id as file friendly id
*/
public static String generateSanitizedId(String id) {
id = id.replace(':', '-');
id = id.replace('_', '-');
id = id.replace('.', '-');
id = id.replace('/', '-');
id = id.replace('\\', '-');
return id;
}
}
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