Java 如何通过键名从 mongoDB 检索值？
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How to retrieve a value from mongoDB, by its key name?
提问by
I am new to mongoDB. I am using java and mongoDB. I have a json like,
我是 mongoDB 的新手。我正在使用 java 和 mongoDB。我有一个像 json
[{ "_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 a collection all doc's have different HomeTown, i just know the key name HomeTown, how can i get the HomeTownvalues?
在一个集合中，所有文档都有不同的HomeTown，我只知道键名HomeTown，我怎样才能得到HomeTown值？
In mongo site, i just can find find()and findOne().
在 mongo 站点中，我只能找到find()和findOne()。
Thanks!
谢谢！
采纳答案by Ron
find()is enough.
find()足够。
db.CollectionName.find({},{HomeTown:1})
in java, it would be:
在java中，它将是：
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"));
}
回答by Hitesh Kumar
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);
}
回答by Dhruv
db.CollectionName.find({},{HomeTown:1,PhoneNumber:0})
Would be wrong, but
会错，但是
db.CollectionName.find({},{HomeTown:1, _id:0})
would be right, because you need to suppress _idexplicitly. Just FYI.
是对的，因为你需要_id明确地压制。仅供参考。
回答by user27
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);
}
}
