How do I push to a nested array in the following structure?
{
level1 : {
- arr1: [
"val1"
]
}
}
I've tried using
coll.update(entry, new BasicDBObject("$push", new BasicDBObject("level1", new BasicDBObject("arr1", "val2"))));
where coll is the collection object and entry is the entry above.
but the value is never pushed and no error is shown. What am I doing wrong?
You can reference the array in the sub-document "level1" using dot notation. So, instead of creating nested DBObjects like you've done, you simply need:
coll.update(entry, new BasicDBObject("$push", new BasicDBObject("level1.arr1", "val2")));
I wrote a test to show this works:
@Test
public void shouldPushANewValueOntoANesstedArray() throws UnknownHostException {
final MongoClient mongoClient = new MongoClient();
final DBCollection coll = mongoClient.getDB("TheDatabase").getCollection("TheCollection");
coll.drop();
//Inserting the array into the database
final BasicDBList array = new BasicDBList();
array.add("val1");
final BasicDBObject entry = new BasicDBObject("level1", new BasicDBObject("arr1", array));
coll.insert(entry);
// results in:
// { "_id" : ObjectId("51a4cfdd3004a84dde78d79c"), "level1" : { "arr1" : [ "val1" ] } }
//do the update
coll.update(entry, new BasicDBObject("$push", new BasicDBObject("level1.arr1", "val2")));
// results in:
// { "_id" : ObjectId("51a4cfdd3004a84dde78d79c"), "level1" : { "arr1" : [ "val1", "val2" ] } }
}
