java后台生成唯一uuid java获取唯一id

import java.lang.management.ManagementFactory;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.util.Enumeration;
import java.util.concurrent.atomic.AtomicInteger;
import java.security.SecureRandom;

/**
 * 对象唯一标识生成器
 * 结构如下:
 *        time(8)-inc(8)-type(4)-machine(8)
 */
public class GUIDGenerator {
   private GUIDGenerator() {
   }

   private static AtomicInteger autoIncCounter = new AtomicInteger(new SecureRandom().nextInt());

private static final int id = identity();// identity for generator

   /**
    * 生成唯一标识,根据机器网卡,JVM和Class Loader生成,以保证唯一
    * 
    * @return int
    */
   private static int identity() {
      final int machinePiece;// identity for machine
      final int processPiece;// identity for process(jvm & classloader)
      try {
         StringBuilder sb = new StringBuilder();
         Enumeration<NetworkInterface> nis = NetworkInterface
               .getNetworkInterfaces();
         while (nis.hasMoreElements()) {
            sb.append(nis.nextElement().toString());
         }
         machinePiece = sb.toString().hashCode();
      } catch (SocketException e) {
         throw new RuntimeException(e);
      }
      // identity for jvm
      StringBuilder sb = new StringBuilder();
      sb.append(ManagementFactory.getRuntimeMXBean().getName());
      // identity classloader
      ClassLoader loader = GUIDGenerator.class.getClassLoader();
      sb.append((loader != null) ? System.identityHashCode(loader) : 0);

      processPiece = sb.toString().hashCode();
      return (machinePiece << 16) | (processPiece & 0xFFFF);
   }

   /**
    * 为对象生成唯一标识(长度为32的16进制形式的字符串)
    * 
    * @param type
    *            领域对象类型
    * @return String
    */
   public static String generate(Class<?> type) {
      return generate(0, type);
   }

   /**
    * 为指定类型对象生成唯一标识(长度为32的16进制形式的字符串)
    * @param type
    *            领域对象类型
    * @return String
    */
   public static String generate(int tenant, Class<?> type) {
      int time = (int) System.currentTimeMillis() / 1000;
      return digits(time, 8) + "-"
            + digits(autoIncCounter.getAndIncrement(), 8) + "-"
            + digits(type.hashCode(), 4) + "-"            
            + digits(id, 8);
   }

   /**
    * 将{@param val}转换成{@param digits}位的16进制数
    */
   private static String digits(int val, int digits) {
      long hi = 1L << (digits * 4);
      return Long.toHexString(hi | (val & (hi - 1))).substring(1);
   }

   /**
    * 获取GUID中的租户id
    *
    * @param guid GUID
    * @return tenantId
    */
   public static int tenantId(String guid){
      String[] components = guid.split("-");
      return Long.decode("0x"+components[3]).intValue();
   }

   public static int type(String guid){
      String[] components = guid.split("-");
      return Long.decode("0x"+components[2]).intValue();
   }

   public static int generator(String guid){
      String[] components = guid.split("-");
      return Long.decode("0x"+components[4]).intValue();
   }

   /**
    * 生成文件名
    *
    * @return machine(8)-inc(8)
    */
   public static String generateName(){
      return  digits(id, 8)
            + digits(autoIncCounter.getAndIncrement(), 8);
   }

}