从嵌套mongodb文档访问值

如何使用Java从子文档（Mongodb）的键/值对访问值

{u id:{“key1”：“val1”}，“key2”：“val2”，“subdoc”：{“key3”：“val3”，“key4”：“val4”}

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在输出中，键3和键4的值为空。有人能告诉我如何访问子文档中的值吗？

请使用以下代码段：

DB db = (new MongoClient("localhost", 27017)).getDB("nov2014");         
DBCollection dbCollection = db.getCollection("student");    

BasicDBObject basicDBObj = new BasicDBObject();
basicDBObj.put("key1", " val1");            

DBCursor dbCursor = dbCollection.find(basicDBObj);          
while(dbCursor.hasNext()){
    BasicDBObject dbObject = (BasicDBObject)dbCursor.next();    
    System.out.println(“Key 2: ” = dbObject.getString("key2");
    System.out.println(“Key 3: ” = ((BasicDBObject)dbObject.get("subdoc")).get("key3");
    System.out.println(“Key 4: ” = ((BasicDBObject)dbObject.get("subdoc")).get("key4");                         
}

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请看答案，因为它是直截了当的，效果很好。顺便说一句，我已经解决了使用-。再次感谢。

DB db = (new MongoClient("localhost", 27017)).getDB("nov2014");         
DBCollection dbCollection = db.getCollection("student");    

BasicDBObject basicDBObj = new BasicDBObject();
basicDBObj.put("key1", " val1");            

DBCursor dbCursor = dbCollection.find(basicDBObj);          
while(dbCursor.hasNext()){
    BasicDBObject dbObject = (BasicDBObject)dbCursor.next();    
    System.out.println(“Key 2: ” = dbObject.getString("key2");
    System.out.println(“Key 3: ” = ((BasicDBObject)dbObject.get("subdoc")).get("key3");
    System.out.println(“Key 4: ” = ((BasicDBObject)dbObject.get("subdoc")).get("key4");                         
}