Find objects by array in mongodb (or java) - mongodb

Question

I've got a collection (dataset) like this:
{
"_id" : ObjectId("515611c1c6e3718ee42a5655"),
"id": "Product1",
"type": "ProductType4"
"productFeature": [
{
"id": "ProductFeature1"
},
{
"id": "ProductFeature2"
},
{
"id": "ProductFeature3"
}
]
"productPropertyNumeric": 25
},
... and more product objects...
{
"_id" : ObjectId("515611c1c6e3718ee42a5666"),
"id": "ProductFeature1",
"label": "blablabla"
},
{
"_id" : ObjectId("515611c1c6e3718ee42a5667"),
"id": "ProductFeature2",
"label": "blebleble"
},
{
"_id" : ObjectId("515611c1c6e3718ee42a5668"),
"id": "ProductFeature3",
"label": "blublublu"
} ... and more feature objects...
According to Product1, I have to find the features and labels that the specific product has in its "productFeature" array.
I have tried in Mongo shell to find them (using a variable, for example):
var aaa = db.dataset.find({ id: "Product1" })
db.dataset.find({ id: "aaa.productFeature.id" })
But it doesn't work. If somebody knows how to find objects by array please help me.
Thanks very much.
PS: It would be best in Java - I apply a query just for example:
BasicDBObject query = new BasicDBObject();
query.put("type","ProductType4");
query.put("productPropertyNumeric", new BasicDBObject("$gt", 10));
DBCursor cursor = coll.find(query).sort( new BasicDBObject("label", 1));
while (cursor.hasNext()){
System.out.println(cursor.next().get("id"));
}

Answer 1

Here is my answer to my own question. I hope this helps to someone.
BasicDBObject query = new BasicDBObject();
BasicDBObject field = new BasicDBObject();
query.put("id", "Product1");
field.put("id", 1);
field.put("productFeature", 1);
field.put("_id", 0);
DBCursor cursor = coll.find(query, field);
while (cursor.hasNext()) {
BasicDBObject result = (BasicDBObject) cursor.next();
System.out.println(result);
ArrayList<BasicDBObject> features = (ArrayList<BasicDBObject>) result.get("productFeature");
for (BasicDBObject embedded : features) {
String featuresId = (String) embedded.get("id");
BasicDBObject query2 = new BasicDBObject();
BasicDBObject field2 = new BasicDBObject();
query2.put("id", featuresId);
field2.put("id", 1);
field2.put("label", 1);
field2.put("_id", 0);
DBCursor cursor2 = coll.find(query2, field2);
while (cursor2.hasNext()) {
System.out.println(cursor2.next());
}
}
}

Answer 2

You have to supply the "path" in the document structure to the field you want to query on from the document root. In this case the path is 'productFeature' --> 'id'. Instead of an arrow MongoDB uses a dot (.), e.g.,
db.dataset.find({ "productFeature.id" : "Product1" });
In Java you do something very similar:
BasicDBObject query = new BasicDBObject("productFeature.id" : "Product1");
DBCursor cursor = coll.find(query).sort( new BasicDBObject("label", 1));
while (cursor.hasNext()){
System.out.println(cursor.next().get("id"));
}

Answer 3

In Java you could also use the Query class in combination with MongoTemplate.
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.data.mongodb.core.query.Criteria;
import org.springframework.data.mongodb.core.query.Query;
#Autowired
private final MongoTemplate mongoTemplate;
...
public YourObjectClass findProduct1(){
Query query = new Query();
query.addCriteria(Criteria.where("productFeature.id").is("Product1"));
List<YourObjectClass> result = this.mongoTemplate.find(query, YourObjectClass.class);
return result;
}