Shulou(Shulou.com)06/01 Report--

Operators such as $in are often used when querying, such as db.collection_0.find ("_ id": {"$in", "0001", "0002", "0003"}).

But how shell should be written in shell,java, take $in as an example here.

PS: I like $in, especially when key is an array type.

I use mongo-java-driver 2.11.0

Now I have a collection named col_0, and I save something like this in it.

Suppose this is a user with an id of 0001 who has 0002 and 0003 friends.

Now I want to query the friends of a user's friends, such as "recommend friends".

For Java code, you can probably write something like this:

DB db = MonFactory.getInstance (). GetMongo (). GetDB ("test"); DBCollection dbCollection = db.getCollection ("col_0"); BasicDBObject term = new BasicDBObject (); term.put ("_ id", uid); DBObject curUserData = dbCollection.findOne (term); List p4pList = new ArrayList (); p4pList.addAll ((Collection)

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