/*
* Copyright (c) 2002-2012 Alibaba Group Holding Limited.
* All rights reserved.
*
* Licensed 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 com.alibaba.citrus.util;
import java.io.DataOutputStream;
import java.lang.reflect.Method;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.security.SecureRandom;
import java.util.concurrent.atomic.AtomicInteger;
import com.alibaba.citrus.util.io.ByteArrayOutputStream;
/**
* 生成唯一ID。
* <p>
* 唯一ID由以下元素构成：<code>machineId-jvmId-timestamp-counter</code>。
* </p>
* <p>
* 默认情况下，UUID由数字和大写字母构成。如果在构造函数时，指定<code>noCase=false</code>
* ，那么所生成的ID将包含小写字母，这样ID的长度会较短。
* </p>
*
* @author Michael Zhou
*/
public class UUID {
private boolean noCase;
private String instanceId;
private AtomicInteger counter;
public UUID() {
this(true);
}
public UUID(boolean noCase) {
// 1. Machine ID - 根据IP/MAC区分
byte[] machineId = getLocalHostAddress();
// 2. JVM ID - 根据启动时间区分 + 随机数
byte[] jvmId = getRandomizedTime();
this.instanceId = StringUtil.bytesToString(machineId, noCase) + "-" + StringUtil.bytesToString(jvmId, noCase);
// counter
this.counter = new AtomicInteger();
this.noCase = noCase;
}
/** 取得local host的地址，如果有可能，取得物理MAC地址。 */
private static byte[] getLocalHostAddress() {
Method getHardwareAddress;
try {
getHardwareAddress = NetworkInterface.class.getMethod("getHardwareAddress");
} catch (Exception e) {
getHardwareAddress = null;
}
byte[] addr;
try {
InetAddress localHost = InetAddress.getLocalHost();
if (getHardwareAddress != null) {
addr = (byte[]) getHardwareAddress.invoke(NetworkInterface.getByInetAddress(localHost)); // maybe null
} else {
addr = localHost.getAddress();
}
} catch (Exception e) {
addr = null;
}
if (addr == null) {
addr = new byte[] { 127, 0, 0, 1 };
}
return addr;
}
/** 取得当前时间，加上随机数。 */
private byte[] getRandomizedTime() {
long jvmId = System.currentTimeMillis();
long random = new SecureRandom().nextLong();
// 取得上述ID的bytes，并转化成字符串
ByteArrayOutputStream baos = new ByteArrayOutputStream();
DataOutputStream dos = new DataOutputStream(baos);
try {
dos.writeLong(jvmId);
dos.writeLong(random);
} catch (Exception e) {
}
return baos.toByteArray().toByteArray();
}
public String nextID() {
// MACHINE_ID + JVM_ID + 当前时间 + counter
return instanceId + "-" + StringUtil.longToString(System.currentTimeMillis(), noCase) + "-"
+ StringUtil.longToString(counter.getAndIncrement(), noCase);
}
}