public String createChat(Jedis conn, String sender, Set<String> recipients, String message) { //啟動的時候redis里是沒有ids:chat:這個鍵的 //自增之后返回1     String chatId = String.valueOf(conn.incr("ids:chat:"));     return createChat(conn, sender, recipients, message, chatId);   }     /**   *   * @param conn   * @param sender 發送消息的人   * @param recipients 接受消息的人   * @param message 待發送的消息   * @param chatId 聊天室的編號   * @return   */   public String createChat( Jedis conn, String sender,      Set<String> recipients, String message, String chatId){   //自己發的消息 自己也能接受到     recipients.add(sender);       Transaction trans = conn.multi();     for (String recipient : recipients){   //聊天室的成員 最開始時 都閱讀的是0號信息       trans.zadd("chat:" + chatId, 0, recipient);   //記錄每個人參加的聊天室       trans.zadd("seen:" + recipient, 0, chatId);     }     trans.exec();       return sendMessage(conn, chatId, sender, message);   }     public String sendMessage(Jedis conn, String chatId, String sender, String message) {      //鎖住聊天室 為啥? 人員變動了咋辦   //這個acquireLock見上一章     String identifier = acquireLock(conn, "chat:" + chatId);     if (identifier == null){       throw new RuntimeException("Couldn't get the lock");     }     try {     //給要發布的消息設定一個最新的編號 第一次時 返回的是1       long messageId = conn.incr("ids:" + chatId);       HashMap<String,Object> values = new HashMap<String,Object>();       values.put("id", messageId);       values.put("ts", System.currentTimeMillis());       values.put("sender", sender);       values.put("message", message);       String packed = new Gson().toJson(values);              //某個聊天室的消息列表       //最舊的消息----消息json        //默認的zset是按照score的值從小到大排序       conn.zadd("msgs:" + chatId, messageId, packed);     }finally{       releaseLock(conn, "chat:" + chatId, identifier);     }     return chatId;   } 

 @SuppressWarnings("unchecked")   public List<ChatMessages> fetchPendingMessages(Jedis conn, String recipient) {      //獲得用戶在各個聊天室 已經看到的最新消息的id   //有幾個聊天室 seenSet的size就是幾     Set<Tuple> seenSet = conn.zrangeWithScores("seen:" + recipient, 0, -1);     List<Tuple> seenList = new ArrayList<Tuple>(seenSet);       Transaction trans = conn.multi();     for (Tuple tuple : seenList){       String chatId = tuple.getElement();       int seenId = (int)tuple.getScore();       //獲取每個聊天室里 未讀的所有消息       //min 和 max 可以是 -inf 和 +inf       trans.zrangeByScore("msgs:" + chatId, String.valueOf(seenId + 1), "inf");     }     //我參加了幾個聊天室 results的長度就是幾     List<Object> results = trans.exec();       //com.google.gson.Gson jar包自己下載吧     Gson gson = new Gson();     Iterator<Tuple> seenIterator = seenList.iterator();     Iterator<Object> resultsIterator = results.iterator();       //用戶最后成功拉取的未讀消息 存放在chatMessages     List<ChatMessages> chatMessages = new ArrayList<ChatMessages>();     List<Object[]> seenUpdates = new ArrayList<Object[]>();     List<Object[]> msgRemoves = new ArrayList<Object[]>();               //這個大的while循環 用戶參與了幾個聊天室 就循環幾次     while (seenIterator.hasNext()){       Tuple seen = seenIterator.next();       Set<String> messageStrings = (Set<String>)resultsIterator.next();       if (messageStrings.size() == 0){       //沒有未讀的消息         continue;       }         //代碼運行到這里       //說明 我在某個聊天室 還有未讀的消息       //seedid記錄我已經拉取到的消息 初始為0       int seenId = 0;       //當前處理的是哪個聊天室       String chatId = seen.getElement();              List<Map<String,Object>> messages = new ArrayList<Map<String,Object>>();              //我在聊天室未讀的消息列表       for (String messageJson : messageStrings){         Map<String,Object> message = (Map<String,Object>)gson.fromJson(           messageJson, new TypeToken<Map<String,Object>>(){}.getType());         int messageId = ((Double)message.get("id")).intValue();           if (messageId > seenId){           seenId = messageId;         }         message.put("id", messageId);         //加入到成功拉取的列表里         messages.add(message);       }       //更新我在這個聊天室讀到的最新消息       conn.zadd("chat:" + chatId, seenId, recipient);              //記錄我在某個聊天室讀到的最新記錄       seenUpdates.add(new Object[]{"seen:" + recipient, seenId, chatId});         //取出第0個member-score       Set<Tuple> minIdSet = conn.zrangeWithScores("chat:" + chatId, 0, 0);       //為啥刪除呢? 每個聊天室是一個zset表 第一條記錄代表的就是 所有用戶至少都讀了的消息       if (minIdSet.size() > 0){       Tuple tuple=minIdSet.iterator().next();       System.out.println("要刪除的 tuple:"+tuple.getElement()+"--"+tuple.getScore());         msgRemoves.add(new Object[]{"msgs:" + chatId, tuple.getScore()});       }       chatMessages.add(new ChatMessages(chatId, messages));     }       trans = conn.multi();     for (Object[] seenUpdate : seenUpdates){       trans.zadd(         (String)seenUpdate[0],         (Integer)seenUpdate[1],         (String)seenUpdate[2]);     }     for (Object[] msgRemove : msgRemoves){       trans.zremrangeByScore(         (String)msgRemove[0], 0, ((Double)msgRemove[1]).intValue());     }     trans.exec();       //返回的是我這次拉取獲得的 最新的消息     return chatMessages;   } 

package redisinaction;   import java.util.Arrays; import java.util.HashSet; import java.util.Iterator; import java.util.List; import java.util.Map; import java.util.Set;   import org.junit.BeforeClass; import org.junit.Test;   import jedis.redis_in_action.Chapter06; import jedis.redis_in_action.Chapter06.ChatMessages; import redis.clients.jedis.Jedis; import redis.clients.jedis.Tuple;   /**   * This class is used for ...   * @author dlf([email protected])  * @version 1.0, 2016年10月17日 下午10:15:58   */ public class Chapter06Test {   static Jedis conn = null;   static Chapter06 c=null;      @BeforeClass   public static void initConn(){     System.out.println("test before");     conn = new Jedis("10.150.0.80");     conn.auth("dlf123123");          c=new Chapter06();   }           @Test    public void testMultiRecipientMessaging() {       System.out.println("/n----- testMultiRecipientMessaging -----");       conn.del("ids:chat:", "msgs:1", "ids:1", "seen:joe", "seen:jeff", "seen:jenny");         System.out.println("Let's create a new chat session with some recipients...");       Set<String> recipients = new HashSet<String>();       recipients.add("jeff");       recipients.add("jenny");       String chatId = c.createChat(conn, "joe", recipients, "message 1");       System.out.println("Now let's send a few messages...");       for (int i = 2; i < 5; i++){         c.sendMessage(conn, chatId, "joe", "message " + i);       }       System.out.println();       System.out.println("看看消息庫");       //消息庫里的所有消息       Set<Tuple> messageFromBase=conn.zrangeWithScores("msgs:"+chatId, 0, -1);       Iterator<Tuple> iterator=messageFromBase.iterator();       while(iterator.hasNext()){         Tuple tuple=iterator.next();         System.out.println(tuple.getElement()+"　－－　　"+tuple.getScore());       }       System.out.println("And let's get the messages that are waiting for jeff and jenny...");                     List<ChatMessages> r1 = c.fetchPendingMessages(conn, "jeff");       List<ChatMessages> r2 = c.fetchPendingMessages(conn, "jenny");     //當我拉取了joe的未讀信息后 就會刪除msgs:1里面的信息     //為什么?想明白了么?       List<ChatMessages> r3 = c.fetchPendingMessages(conn, "joe");       System.out.println("They are the same? " + r1.equals(r2));              System.out.println("Those messages are:");       for(ChatMessages chat : r1){         System.out.println(" chatId: " + chat.chatId);         System.out.println("  messages:");         for(Map<String,Object> message : chat.messages){           System.out.println("   " + message);         }       }         System.out.println("看看還有沒");       messageFromBase=conn.zrangeWithScores("msgs:"+chatId, 0, -1);        iterator=messageFromBase.iterator();       while(iterator.hasNext()){         Tuple tuple=iterator.next();         System.out.println(tuple.getElement()+"　－－　　"+tuple.getScore());       }       conn.del("ids:chat:", "msgs:1", "ids:1", "seen:joe", "seen:jeff", "seen:jenny");     }    }