MongoDB [Java]：如何以字節[]格式查詢存儲的UUID？

Question

我想查詢存儲在我的MongoDB中的java.util.UUID，使用與存儲的UUID所基於的字符串相對應的字節[]。

我見過Mongo Driver自動將UUID轉換爲字節並將其存儲爲BinData（子類型）。下面是我用來保存UUID代碼：

 UUID originalUUID= UUID.fromString("7ee973c0-54b5-11e4-aaed-0002a5d5c51b"); 
     MongoClient mongoClient = new MongoClient("localhost" , 27017); 
     DB db = mongoClient.getDB("test"); 
     DBCollection coll = db.getCollection("test"); 

     BasicDBObject query = new BasicDBObject("_id", originalUUID); 
     coll.save(query); 

我知道我們可以很容易地檢索與UUID對象在BasicDBObject值這個文件，但是我想用一個byte []代替。畢竟，它在我的Mongo中必須是字節嗎？ 我知道Java在發送給Mongo之前搞亂了字節順序，但是我一直無法使它工作。我的檢索代碼是在這裏：

 String stringOne = "7ee973c0-54b5-11e4-aaed-0002a5d5c51b"; 
     // It's the same UUID String 

     BasicDBObject find = new BasicDBObject("_id", stringOne.getBytes()); 

     DBCursor cursor = null; 
     cursor = coll.find(find); 
     while(cursor.hasNext()){ 
      BasicDBObject dbObject = (BasicDBObject)cursor.next(); 
      byte[] received = (byte[])dbObject.get("_id"); 
      System.out.println(new String(received)); 
     } 

我也試過小端編碼是這樣的：

 byte[] bytes = new byte[16]; 
     ByteBuffer bb = ByteBuffer.wrap(bytes); 
     bb.order(ByteOrder.LITTLE_ENDIAN); 

     bb.putLong(originalUUID.getMostSignificantBits()); 
     bb.putLong(originalUUID.getLeastSignificantBits()); 

     BasicDBObject find = new BasicDBObject("_id", bb.array()); //Also tried flipping bb. 

這一切都不奏效。有人可以通過解決方案提供一些見解嗎？

謝謝！

Answer 1

你非常接近。它不工作的唯一原因是查詢匹配器也匹配二進制的子類型。試試這個：

UUID originalUUID = UUID.fromString("7ee973c0-54b5-11e4-aaed-0002a5d5c51b"); 
    MongoClient mongoClient = new MongoClient(); 
    DB db = mongoClient.getDB("test"); 
    DBCollection coll = db.getCollection("test"); 

    BasicDBObject query = new BasicDBObject("_id", originalUUID); 
    coll.save(query); 

    byte[] bytes = new byte[16]; 
    ByteBuffer bb = ByteBuffer.wrap(bytes); 
    bb.order(ByteOrder.LITTLE_ENDIAN); 

    bb.putLong(originalUUID.getMostSignificantBits()); 
    bb.putLong(originalUUID.getLeastSignificantBits()); 

    System.out.println(coll.findOne(originalUUID)); 
    System.out.println(coll.findOne(new Binary(Bytes.B_UUID, bb.array()))); // note use of the B_UUID subtype 

它應該打印：

{ "_id" : { "$uuid" : "7ee973c0-54b5-11e4-aaed-0002a5d5c51b"}} 
    { "_id" : { "$uuid" : "7ee973c0-54b5-11e4-aaed-0002a5d5c51b"}}