mongodb 3.2 java driver aggregation whith match on lookup - mongodb

Question

I wonder how to perform the aggregation $match on a $lookup collection with the java driver for mongodb 3.2. Here is the structure of the two collections i am working on :
coll_one:{
_id : ObjectId("hex_string"),
foreign_id : ObjectId("hex_string") **the id of coll_two**}
coll_two:{
_id : ObjectId("hex_string"),
actif : true,
closed : false }
The lookup on the two ids (coll_one.foreign_id & coll_two._id) seems to work fine. But when i specify a match on coll_two.actif = true, it returns an empty result.
This is the Java code i'am using :
Bson lookup = new Document("$lookup",
new Document("from", "coll_two" )
.append("localField", "foreign_id")
.append("foreignField", "_id")
.append("as", "look_coll"));
List<Bson> filters = new ArrayList<Bson>();
filters.add(lookup);
//here is the MATCH
filters.add(match(eq("look_coll.actif",true)));
DB().getCollection("coll_one").aggregate(filters);
Evrything works fine whene i remove the match section. I have tried so many combination of possibilities with no success at all !!!
Can any body tells me if this is possible ????

Answer 1

Add your $match request to a Document instance :
Bson match = new Document("$match",
new Document("look_coll.actif", true));
filters.add(match);
Here is a full example :
MongoClient mongoClient = new MongoClient("localhost");
MongoDatabase db = mongoClient.getDatabase("mydb");
Bson lookup = new Document("$lookup",
new Document("from", "coll_two")
.append("localField", "foreign_id")
.append("foreignField", "_id")
.append("as", "look_coll"));
Bson match = new Document("$match",
new Document("look_coll.actif", true));
List<Bson> filters = new ArrayList<>();
filters.add(lookup);
filters.add(match);
AggregateIterable<Document> it = db.getCollection("coll_one").aggregate(filters);
for (Document row : it) {
System.out.println(row.toJson());
}