怎样用java生成GUID与UUID

   GUID是一个128位长的数字，一般用16进制表示。算法的核心思想是结合机器的网卡、当地时间、一个随机数来生成GUID。从理论上讲，如果一台机器每秒产生10000000个GUID，则可以保证（概率意义上）3240年不重复。

    UUID是1.5中新增的一个类，在java.util下，用它可以产生一个号称全球唯一的ID
Java代码
import java.util.UUID;  
public class Test {  
public static void main(String[] args) {  
  UUID uuid = UUID.randomUUID();   
  System.out.println (uuid);  
}  
} 

import java.util.UUID;
public class Test {
public static void main(String[] args) {
  UUID uuid = UUID.randomUUID();
  System.out.println (uuid);
}
}编译运行输出：
07ca3dec-b674-41d0-af9e-9c37583b08bb


两种方式生成guid 与uuid

需要comm log 库

Java代码
/** 
* @author Administrator 
* 
* TODO To change the template for this generated type comment go to 
* Window - Preferences - Java - Code Style - Code Templates 
*/ 
import java.net.InetAddress;  
import java.net.UnknownHostException;  
import java.security.MessageDigest;  
import java.security.NoSuchAlgorithmException;  
import java.security.SecureRandom;  
import java.util.Random;  
 
public class RandomGUID extends Object {  
   protected final org.apache.commons.logging.Log logger = org.apache.commons.logging.LogFactory  
      .getLog(getClass());  
 
   public String valueBeforeMD5 = "";  
   public String valueAfterMD5 = "";  
   private static Random myRand;  
   private static SecureRandom mySecureRand;  
 
   private static String s_id;  
   private static final int PAD_BELOW = 0x10;  
   private static final int TWO_BYTES = 0xFF;  
 
   /* 
    * Static block to take care of one time secureRandom seed. 
    * It takes a few seconds to initialize SecureRandom.  You might 
    * want to consider removing this static block or replacing 
    * it with a "time since first loaded" seed to reduce this time. 
    * This block will run only once per JVM instance. 
      */ 
 
   static {  
      mySecureRand = new SecureRandom();  
      long secureInitializer = mySecureRand.nextLong();  
      myRand = new Random(secureInitializer);  
      try {  
         s_id = InetAddress.getLocalHost().toString();  
      } catch (UnknownHostException e) {  
         e.printStackTrace();  
      }  
 
   }  
 
 
   /* 
    * Default constructor.  With no specification of security option, 
    * this constructor defaults to lower security, high performance. 
    */ 
   public RandomGUID() {  
      getRandomGUID(false);  
   }  
 
   /* 
    * Constructor with security option.  Setting secure true 
    * enables each random number generated to be cryptographically 
    * strong.  Secure false defaults to the standard Random function seeded 
    * with a single cryptographically strong random number. 
    */ 
   public RandomGUID(boolean secure) {  
      getRandomGUID(secure);  
   }  
 
   /* 
    * Method to generate the random GUID 
    */ 
   private void getRandomGUID(boolean secure) {  
      MessageDigest md5 = null;  
      StringBuffer sbValueBeforeMD5 = new StringBuffer(128);  
 
      try {  
         md5 = MessageDigest.getInstance("MD5");  
      } catch (NoSuchAlgorithmException e) {  
         logger.error("Error: " + e);  
      }  
 
      try {  
         long time = System.currentTimeMillis();  
         long rand = 0;  
 
         if (secure) {  
            rand = mySecureRand.nextLong();  
         } else {  
            rand = myRand.nextLong();  
         }  
         sbValueBeforeMD5.append(s_id);  
         sbValueBeforeMD5.append(":");  
         sbValueBeforeMD5.append(Long.toString(time));  
         sbValueBeforeMD5.append(":");  
         sbValueBeforeMD5.append(Long.toString(rand));  
 
         valueBeforeMD5 = sbValueBeforeMD5.toString();  
         md5.update(valueBeforeMD5.getBytes());  
 
         byte[] array = md5.digest();  
         StringBuffer sb = new StringBuffer(32);  
         for (int j = 0; j < array.length; ++j) {  
            int b = array[j] & TWO_BYTES;  
            if (b < PAD_BELOW)  
               sb.append('0');  
            sb.append(Integer.toHexString(b));  
         }  
 
         valueAfterMD5 = sb.toString();  
 
      } catch (Exception e) {  
         logger.error("Error:" + e);  
      }  
   }  
 
   /* 
    * Convert to the standard format for GUID 
    * (Useful for SQL Server UniqueIdentifiers, etc.) 
    * Example: C2FEEEAC-CFCD-11D1-8B05-00600806D9B6 
    */ 
   public String toString() {  
      String raw = valueAfterMD5.toUpperCase();  
      StringBuffer sb = new StringBuffer(64);  
      sb.append(raw.substring(0,);  
      sb.append("-");  
      sb.append(raw.substring(8, 12));  
      sb.append("-");  
      sb.append(raw.substring(12, 16));  
      sb.append("-");  
      sb.append(raw.substring(16, 20));  
      sb.append("-");  
      sb.append(raw.substring(20));  
 
      return sb.toString();  
   }  
 
 
     // Demonstraton and self test of class  
     public static void main(String args[]) {  
       for (int i=0; i< 100; i++) {  
         RandomGUID myGUID = new RandomGUID();  
         System.out.println("Seeding String=" + myGUID.valueBeforeMD5);  
         System.out.println("rawGUID=" + myGUID.valueAfterMD5);  
         System.out.println("RandomGUID=" + myGUID.toString());  
       }  
     }  
 
 
} 

/**
* @author Administrator
*
* TODO To change the template for this generated type comment go to
* Window - Preferences - Java - Code Style - Code Templates
*/
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.Random;

public class RandomGUID extends Object {
   protected final org.apache.commons.logging.Log logger = org.apache.commons.logging.LogFactory
      .getLog(getClass());

   public String valueBeforeMD5 = "";
   public String valueAfterMD5 = "";
   private static Random myRand;
   private static SecureRandom mySecureRand;

   private static String s_id;
   private static final int PAD_BELOW = 0x10;
   private static final int TWO_BYTES = 0xFF;

   /*
    * Static block to take care of one time secureRandom seed.
    * It takes a few seconds to initialize SecureRandom.  You might
    * want to consider removing this static block or replacing
    * it with a "time since first loaded" seed to reduce this time.
    * This block will run only once per JVM instance.
      */

   static {
      mySecureRand = new SecureRandom();
      long secureInitializer = mySecureRand.nextLong();
      myRand = new Random(secureInitializer);
      try {
         s_id = InetAddress.getLocalHost().toString();
      } catch (UnknownHostException e) {
         e.printStackTrace();
      }

   }


   /*
    * Default constructor.  With no specification of security option,
    * this constructor defaults to lower security, high performance.
    */
   public RandomGUID() {
      getRandomGUID(false);
   }

   /*
    * Constructor with security option.  Setting secure true
    * enables each random number generated to be cryptographically
    * strong.  Secure false defaults to the standard Random function seeded
    * with a single cryptographically strong random number.
    */
   public RandomGUID(boolean secure) {
      getRandomGUID(secure);
   }

   /*
    * Method to generate the random GUID
    */
   private void getRandomGUID(boolean secure) {
      MessageDigest md5 = null;
      StringBuffer sbValueBeforeMD5 = new StringBuffer(128);

      try {
         md5 = MessageDigest.getInstance("MD5");
      } catch (NoSuchAlgorithmException e) {
         logger.error("Error: " + e);
      }

      try {
         long time = System.currentTimeMillis();
         long rand = 0;

         if (secure) {
            rand = mySecureRand.nextLong();
         } else {
            rand = myRand.nextLong();
         }
         sbValueBeforeMD5.append(s_id);
         sbValueBeforeMD5.append(":");
         sbValueBeforeMD5.append(Long.toString(time));
         sbValueBeforeMD5.append(":");
         sbValueBeforeMD5.append(Long.toString(rand));

         valueBeforeMD5 = sbValueBeforeMD5.toString();
         md5.update(valueBeforeMD5.getBytes());

         byte[] array = md5.digest();
         StringBuffer sb = new StringBuffer(32);
         for (int j = 0; j < array.length; ++j) {
            int b = array[j] & TWO_BYTES;
            if (b < PAD_BELOW)
               sb.append('0');
            sb.append(Integer.toHexString(b));
         }

         valueAfterMD5 = sb.toString();

      } catch (Exception e) {
         logger.error("Error:" + e);
      }
   }

   /*
    * Convert to the standard format for GUID
    * (Useful for SQL Server UniqueIdentifiers, etc.)
    * Example: C2FEEEAC-CFCD-11D1-8B05-00600806D9B6
    */
   public String toString() {
      String raw = valueAfterMD5.toUpperCase();
      StringBuffer sb = new StringBuffer(64);
      sb.append(raw.substring(0,);
      sb.append("-");
      sb.append(raw.substring(8, 12));
      sb.append("-");
      sb.append(raw.substring(12, 16));
      sb.append("-");
      sb.append(raw.substring(16, 20));
      sb.append("-");
      sb.append(raw.substring(20));

      return sb.toString();
   }


     // Demonstraton and self test of class
     public static void main(String args[]) {
       for (int i=0; i< 100; i++) {
         RandomGUID myGUID = new RandomGUID();
         System.out.println("Seeding String=" + myGUID.valueBeforeMD5);
         System.out.println("rawGUID=" + myGUID.valueAfterMD5);
         System.out.println("RandomGUID=" + myGUID.toString());
       }
     }


}

同样

Java代码
UUID uuid = UUID.randomUUID();  
System.out.println("{"+uuid.toString()+"}"); 

UUID uuid = UUID.randomUUID();
System.out.println("{"+uuid.toString()+"}");

UUID是指在一台机器上生成的数字，它保证对在同一时空中的所有机器都是唯一的。通常平台会提供生成UUID的API。UUID按照开放软件基金会(OSF)制定的标准计算，用到了以太网卡地址、纳秒级时间、芯片ID码和许多可能的数字。由以下几部分的组合：当前日期和时间(UUID的第一个部分与时间有关，如果你在生成一个UUID之后，过几秒又生成一个UUID，则第一个部分不同，其余相同)，时钟序列，全局唯一的IEEE机器识别号（如果有网卡，从网卡获得，没有网卡以其他方式获得），UUID的唯一缺陷在于生成的结果串会比较长。关于UUID这个标准使用最普遍的是微软的GUID(Globals Unique Identifiers)。

评论

1 楼 wentao365 2011-11-18  

明明是　３２位啊。怎么是１２８　位呢？