java唯一ID生成

package com.taobao.tddl.client.util;import java.io.IOException;import java.io.UnsupportedEncodingException;import java.net.InetAddress;import java.security.MessageDigest;import java.security.NoSuchAlgorithmException;import java.security.SecureRandom;import java.util.HashMap;import java.util.Map;import java.util.Random;import java.util.concurrent.atomic.AtomicLong;import java.util.concurrent.locks.ReentrantLock;/** * @author huangshang *  */public class UniqId {private static char[] digits = { '0', '1', '2', '3', '4', '5', '6', '7','8', '9', 'a', 'b', 'c', 'd', 'e', 'f' };private static Map<Character, Integer> rDigits = new HashMap<Character, Integer>(16);static {for (int i = 0; i < digits.length; ++i) {rDigits.put(digits[i], i);}}private static UniqId me = new UniqId();private String hostAddr;private Random random = new SecureRandom();private MessageDigest mHasher;private UniqTimer timer = new UniqTimer();private ReentrantLock opLock = new ReentrantLock();private UniqId() {try {InetAddress addr = InetAddress.getLocalHost();hostAddr = addr.getHostAddress();} catch (IOException e) {hostAddr = String.valueOf(System.currentTimeMillis());}if (hostAddr == null || hostAddr.length() == 0|| "127.0.0.1".equals(hostAddr)) {hostAddr = String.valueOf(System.currentTimeMillis());}try {mHasher = MessageDigest.getInstance("MD5");} catch (NoSuchAlgorithmException nex) {mHasher = null;}}/** * 获取UniqID实例 *  * @return UniqId */public static UniqId getInstance() {return me;}/** * 获得不会重复的毫秒数 *  * @return */public long getUniqTime() {return timer.getCurrentTime();}/** * 获得UniqId *  * @return uniqTime-randomNum-hostAddr-threadId */public String getUniqID() {StringBuffer sb = new StringBuffer();long t = timer.getCurrentTime();sb.append(t);sb.append("-");sb.append(random.nextInt(8999) + 1000);sb.append("-");sb.append(hostAddr);sb.append("-");sb.append(Thread.currentThread().hashCode());return sb.toString();}/** * 获取MD5之后的uniqId string *  * @return uniqId md5 string */public String getUniqIDHashString() {return hashString(getUniqID());}/** * 获取MD5之后的uniqId *  * @return byte[16] */public byte[] getUniqIDHash() {return hash(getUniqID());}/** * 对字符串进行md5 *  * @param str * @return md5 byte[16] */public byte[] hash(String str) {opLock.lock();try {byte[] bt = mHasher.digest(str.getBytes("UTF-8"));if (null == bt || bt.length != 16) {throw new IllegalArgumentException("md5 need");}return bt;} catch (UnsupportedEncodingException e) {throw new RuntimeException("unsupported utf-8 encoding", e);} finally {opLock.unlock();}}/** * 对二进制数据进行md5 *  * @param str * @return md5 byte[16] */public byte[] hash(byte[] data) {opLock.lock();try {byte[] bt = mHasher.digest(data);if (null == bt || bt.length != 16) {throw new IllegalArgumentException("md5 need");}return bt;} finally {opLock.unlock();}}/** * 对字符串进行md5 string *  * @param str * @return md5 string */public String hashString(String str) {byte[] bt = hash(str);return bytes2string(bt);}/** * 对字节流进行md5 string *  * @param str * @return md5 string */public String hashBytes(byte[] str) {byte[] bt = hash(str);return bytes2string(bt);}/** * 将一个字节数组转化为可见的字符串 *  * @param bt * @return */public String bytes2string(byte[] bt) {int l = bt.length;char[] out = new char[l << 1];for (int i = 0, j = 0; i < l; i++) {out[j++] = digits[(0xF0 & bt[i]) >>> 4];out[j++] = digits[0x0F & bt[i]];}return new String(out);}/** * 将字符串转换为bytes *  * @param str * @return byte[] */public byte[] string2bytes(String str) {if (null == str) {throw new NullPointerException("参数不能为空");}if (str.length() != 32) {throw new IllegalArgumentException("字符串长度必须是32");}byte[] data = new byte[16];char[] chs = str.toCharArray();for (int i = 0; i < 16; ++i) {int h = rDigits.get(chs[i * 2]).intValue();int l = rDigits.get(chs[i * 2 + 1]).intValue();data[i] = (byte) ((h & 0x0F) << 4 | (l & 0x0F));}return data;}/** * 实现不重复的时间 *  * @author dogun */private static class UniqTimer {private AtomicLong lastTime = new AtomicLong(System.currentTimeMillis());public long getCurrentTime() {return this.lastTime.incrementAndGet();}}}