Mongo DB Update to a sub array document - mongodb

Question

I have a structure
{
"_id" : ObjectId("562dfb4c595028c9r74fda67"),
"office_id" : "123456",
"employee" : [
{
"status" : "declined",
"personId" : "123456",
"updated" : NumberLong("1428407042401")
}
]
}
This office can have multiple persons.Is there a way if I want to update the employee status for all the person under that specific office_id to say "approved".I am trying the same through plain mongo java driver.What I am trying is get all the office id using a query builder , then iterate over the list and save the document.Somewhat I am not satisfied with the iterative approach(fetch,iterate and save ) that I am following.Please suggest if there is alternative way.

Answer 1

You can update using the $ positional operator:
db.collection.update(
{
"office_id" : "123456",
"employee.status": "declined"
},
{
"$set": { "employee.$.status": "approved" }
}
);
The positional operator saves the index (0 in the case above) of the element from the array that matched the query. This means that if you knew the position of the element beforehand (which is nearly impossible in a real life case), you could just change the update statement to: {"$set": {"employee.0.status": "approved"}}.
Please note that the $ positional operator (for now) updates the first relevant document ONLY, there is a JIRA ticket for this.
EDIT:
Using the Java driver, the above update may be done like so (untested):
BasicDBObject update = new BasicDBObject();
BasicDBObject query = new BasicDBObject();
query.put("office_id", "123456");
query.put("employee.status", "declined");
BasicDBObject set = new BasicDBObject("$set", update);
update.put(""employee.$.status", "approved");
collection.update(query, set);