Wie kann man einen Wert von mongoDB mit seinem Schlüsselnamen abrufen?

Question

Ich bin neu in mongoDB. Ich benutze Java und MongoDB. Ich habe eine json wie

[{ "_id" : { "$oid" : "4ceb753a70fdf877ef5113ca"} , "HomeTown" : "AA" , 
"PhoneNumber" : { "CustName" : "xxx" , "Number" : "3403290"}, 
"MobileNumber" : { "CustName" : "yyy" , "Number" : "9323304302"}}] 

    [{ "_id" : { "$oid" : "4ceb753a70fdf877ef5113ca"} , "HomeTown" : "AA" , 
"PhoneNumber" : { "CustName" : "xxx" , "Number" : "3403290"}, 
"MobileNumber" : { "CustName" : "yyy" , "Number" : "9323304302"}}] 

    [{ "_id" : { "$oid" : "4ceb753a70fdf877ef5113ca"} , "HomeTown" : "BB" , 
"PhoneNumber" : { "CustName" : "xxx" , "Number" : "3403290"}, 
"MobileNumber" : { "CustName" : "yyy" , "Number" : "9323304302"}}] 

    [{ "_id" : { "$oid" : "4ceb753a70fdf877ef5113ca"} , "HomeTown" : "BB" , 
"PhoneNumber" : { "CustName" : "xxx" , "Number" : "3403290"}, 
"MobileNumber" : { "CustName" : "yyy" , "Number" : "9323304302"}}] 

In einer Sammlung aller doc haben unterschiedliche HomeTown, ich weiß nur, die Schlüsselnamen HomeTown, wie kann ich die HomeTown Werte bekommen?

In Mongo Website kann ich nur find() und findOne() finden.

Danke!

Answer 1

find() ist genug.

db.CollectionName.find({},{HomeTown:1}) 

in java, wäre es:

BasicDBObject query = new BasicDBObject(); 
BasicDBObject field = new BasicDBObject(); 
field.put("HomeTown", 1); 
DBCursor cursor = db.getCollection(collectionName).find(query,field); 
while (cursor.hasNext()) { 
    BasicDBObject obj = (BasicDBObject) cursor.next(); 
    result.add(obj.getString("HomeTown")); 
} 

Answer 2

Mongo m = new Mongo('localhost',27017); 
DB db = m.getDB("yourDBName"); 
Collection coll = db.getCollection("yourCollectionName") 
BasicDBObject query = new BasicDBObject(); 
query.put("HomeTown", 1); 
DBCursor cursor = coll.find(query); 
ArrayList arr = new ArrayList(); 
String str; 
while (cursor.hasNext()) { 
    str=cursor.curr().get("HomeTown").toString(); 
    arr.add(str); 
} 

Answer 3

db.CollectionName.find({},{HomeTown:1,PhoneNumber:0}) 

falsch wäre, aber

db.CollectionName.find({},{HomeTown:1, _id:0}) 

würde richtig sein, weil Sie _id explizit zu unterdrücken müssen . Nur zu deiner Information.

Answer 4

for(int value=0;value<=10;value++) 
{ 
DBCollection tableDetails = db.getCollection("Collection Name"); 
BasicDBObject queryDetails = new BasicDBObject(); 
queryDetails.put("_id", value); 
DBCursor cursorDetails =tableDetails.find(queryDetails); 
DBObject oneDetails; 
boolean Name=cursorDetails.hasNext(); 
while(Name) 
    { 
    oneDetails=cursorDetails.next();   
    String data=oneDetails.get("HomeTown").toString(); 
    System.out.println(data); 
    } 
}