MongoDB/Java SDK: Query elements with a value in array

Question

I am very new to MongoDB and its Java... SDK? Api? I have a very simple question, but I haven't been able to find a satisfactory answer.

Let's say I have a collection of instances that are like:

{
    "_id": {
        "$oid": "5156171e5d451c136236e738"
    },
    "_types": [
        "Sample"
    ],
    "last_z": {
        "$date": "2012-12-30T09:12:12.250Z"
    },
    "last": {
        "$date": "2012-12-30T04:12:12.250Z"
    },
    "section": "5156171e5d451c136236e70f",
    "s_mac": "AA:AA:AA:AA:AA:AA",
    "_cls": "Sample",
}

And I have a hard-coded Java list:

static List<String> MAC_LIST = Arrays.asList("90:27:E4:0E:3D:D2", "A8:26:D9:E6:1D:8B");

What I would like to know is how to query the MongoDB so it will give me all the objects whose s_mac field has a value that appears in the MAC_LIST List.

I'm guessing I should use the $in operator, but I don't know how to translate it to Java code.

Any hint or link to pages with explanations of the use of the $in operator through the Java SDK would be appreciated!

Mmmm... how is Java going to know that the field I want to look for is actually "s_mac"? — Savir
– Savir, Commented Apr 1, 2013 at 21:00
Missed a bit: collection.find(new BasicDBObject("s_mac", new BasicDBObject("$in", MAC_LIST))); — assylias
– assylias, Commented Apr 1, 2013 at 21:02
Is not giving me any error, but apparently the resulting query doesn't have any "next" (and there's at least 2 instances int he collection with an s_mac contained in the array, though)... I'm gonna keep looking... It looks promising! :) — Savir
– Savir, Commented Apr 1, 2013 at 21:08
I just tried on a similar example and it worked as expected - not sure why you don't get anything back. You could try in the shell to see what you get: db.yourcollection.find({s_mac: {$in: ["90:27:E4...", "A8:26..."]}}). Also note that you can use a for-each loop with the result of a find: Iterable<DBObject> result = collection.find(); for (DBObject o : result) {...} — assylias
– assylias, Commented Apr 1, 2013 at 21:15
Yeah, through the mongo terminal, I get 3 items whose s_mac is in the array > db.getCollection("myCollection").find({s_mac: {$in: ["90:27:E4:0E:3D:D2", "A8:26:D9:E6:1D:8B"]}}).count() 3 — Savir
– Savir, Commented Apr 1, 2013 at 21:26

assylias · Accepted Answer · 2013-04-01 21:45:58Z

4

Here is a contrived example that works for me (driver version 2.10.1) - you can adjust the IP address and run it as is to check if you get the same outcome:

public void gss() throws Exception{
    MongoClient mongo = new MongoClient("192.168.1.1");
    DB db = mongo.getDB("test");
    DBCollection collection = db.getCollection("stackoverflow");
    DBObject o1 = new BasicDBObject();
    o1.put("s_mac", "AA:AA:AA:AA:AA:AA");
    o1.put("_cls", "Sample1");
    DBObject o2 = new BasicDBObject();
    o2.put("s_mac", "90:27:E4:0E:3D:D2");
    o2.put("_cls", "Sample2");
    DBObject o3 = new BasicDBObject();
    o3.put("s_mac", "A8:26:D9:E6:1D:8B");
    o3.put("_cls", "Sample3");
    collection.insert(o1, o2, o3);
    System.out.println(collection.find().count());
    List<String> MAC_LIST = Arrays.asList("90:27:E4:0E:3D:D2", "A8:26:D9:E6:1D:8B");
    System.out.println(collection.find(new BasicDBObject("s_mac", new BasicDBObject("$in", MAC_LIST))).count());
}

It inserts the following documents:

{ "_id" : ObjectId("5159ff98567e143bff0668e9"),
  "s_mac" : "AA:AA:AA:AA:AA:AA",
  "_cls" : "Sample1"
}
{ "_id" : ObjectId("5159ff98567e143bff0668ea"),
  "s_mac" : "90:27:E4:0E:3D:D2",
  "_cls" : "Sample2"
}
{ "_id" : ObjectId("5159ff98567e143bff0668eb"),
  "s_mac" : "A8:26:D9:E6:1D:8B",
  "_cls" : "Sample3"
}

A call to collection.find().count() returns 3 and a call to collection.find(new BasicDBObject("s_mac", new BasicDBObject("$in", MAC_LIST))).count() returns 2 which I think is what you expected.

answered Apr 1, 2013 at 21:45

assylias

330k84 gold badges680 silver badges806 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Savir Over a year ago

Yep, actually, what you said in your comment was working. It was my freaking fault it wouldn't work! But this is a very good answer. I'm sure it'll help many people (is the first time one of my questions gets 3 upvotes in like... 20 minutes, which makes me believe that many people were wondering the same). Thank you again!! :)

Collectives™ on Stack Overflow

MongoDB/Java SDK: Query elements with a value in array

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related