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Project in MongoDB Aggregation Framework

I am trying to use the $project operator in the aggregation-framework with MongoDB for Java.
DBObject fields = new BasicDBObject("example", 1);
fields.put("timestamp", $timestampField);
The above results in "exception: Unrecognized pipeline stage name: 'timestamp'" , "code" : 16436 , "ok" : 0.0}

If what you are trying to $project is basically something that serializes like this:
{ "$project": {
"example": 1,
"timestamp": "$timestameField"
}}
Then you construct your BSON accordingly, and pretty much exactly as shown:
DBObject project = new BasicDBObject(
"$project", new BasicDBObject(
"example", 1
).append(
"timestamp", "$timestamp"
)
);
It is the .append() method that adds additional field content. The .put() method "replaces" the content in the BasicDBObject.

Convert mongoDB shell command to java

I am trying to convert the mongodb shell code below to java. However, i run into some problems doing so. Can anyone help me with this issue?
MongoDB
var friend_ids = db.users.findOne(ObjectId("...")).friend_ids
db.users.find({_id:{$in:friend_ids}})
Java
ObjectId id = new ObjectId("...");
BasicDBObject fields = new BasicDBObject("friend_ids", 1).append("_id", false);
DBObject f_ids = coll.findOne(id, fields);
BasicDBObject query = new BasicDBObject("_id",(new BasicDBObject("$in", f_ids)));
DBCursor cursor = coll.find(query);
The java query is as follows.
query={ "_id" : { "$in" : { "friend_ids" : [ { "$oid" : "..."} , { "$oid" : "..."} , { "$oid" : "..."}]}}},
thanks

You need extract friend_ids from f_ids.
BasicDBObject query = new BasicDBObject("_id",(new BasicDBObject("$in", f_ids.get("friend_ids"))));

Aggregation Framework - Group Operation throw NumberFormatException

I'm using Spring-Data MongoDB aggregation framework.
Here is a code sample:
Aggregation agg = Aggregation.newAggregation(
match(Criteria.where("type").is("PROMO")),
group("locale")//.count().as("counts")
);
AggregationResults<Message> results = mongoTemplate.aggregate(agg, "message", Message.class);
return results.getMappedResults();
Throw:
org.springframework.core.convert.ConversionFailedException: Failed to convert from type java.lang.String to type java.math.BigDecimal for value 'CL'; nested exception is java.lang.NumberFormatException
CL is a value on locale field, but i dont understand why throw that exception.
Im using a similar example from the documentation.
SOLVED:
Aggregation agg = Aggregation.newAggregation(
match(Criteria.where("type").is("PROMO")),
group("created", "text").addToSet("locale").as("countries").addToSet("device.deviceType").as("platforms").count().as("count")
);
I try a simple example on mongo console. After that, map the operations to the builder.
I dont undesrtand why dont work before. If someone can clear the problem will be great.
The model "message":
{ "_id" : "90.0", "device" : { "_id" : "5faf92fd-37f2-4d42-a01a-dd1abce0c1af", "deviceType" : "iPhone", "countryId" : "AR" }, "text" : "Text", "created" : ISODate("2014-01-03T15:56:27.096Z"), "status" : "SENT", "type" : "PROMO" }

My simple answer is avoid using the MongoDB Spring Data classes directly for aggregation and use the standard MongoDB Java objects e.g. DBObject / AggregationOutput. The reason for that is I have lost several hours trying to get anything but basic aggregation queries working in MongoDB Spring data (and that is using the latest which as of today is spring-data-mongodb 1.5.0.RELEASE).
However, constructing aggregation queries using the standard MongoDB Java objects can be a pain (especially if nested / complex) as you end up creating countless DBObject groupFields = new BasicDBObject("_id", null); and the code looks a mess.
I recommend adding the following 3 wrapper methods to your code.
protected DBObject dbObj (String key, Object value) {
return new BasicDBObject (key, value);
}
protected DBObject dbObj (Object ... objs) {
DBObject dbObj = new BasicDBObject();
if (objs.length % 2 == 0) {
for (int i = 0; i < objs.length; i+=2) {
dbObj.put((String)objs[i], objs[i+1]);
}
}
return dbObj;
}
protected DBObject dbList (Object ... objs) {
BasicDBList dbList = new BasicDBList();
for (Object obj : objs) {
dbList.add(obj);
}
return (DBObject)dbList;
}
This enables easy translation between your JSON based queries and your Java code. e.g. if you had the following complex query (taken from http://docs.mongodb.org/manual/tutorial/aggregation-zip-code-data-set/)
db.zipcodes.aggregate(
{
$group: {
_id: { state: "$state", city: "$city" },
pop: { $sum: "$pop" }
}
},{
$sort: { pop: 1 }
},{
$group: {
_id: "$_id.state",
biggestCity: { $last: "$_id.city" },
biggestPop: { $last: "$pop" },
smallestCity: { $first: "$_id.city" },
smallestPop: { $first: "$pop" }
}
},{
$project: {
_id: 0,
state: "$_id",
biggestCity: {
name: "$biggestCity",
pop: "$biggestPop"
},
smallestCity: {
name: "$smallestCity",
pop: "$smallestPop"
}
}
});
... then your Java code would look something like this ...
List<DBObject> aggregation = Arrays.asList (
dbObj ("$group", dbObj (
"_id", dbObj ("state", "$state", "city", "$city"),
"pop", dbObj ("$sum", "$post")
)),
dbObj ("$sort", dbObj ("pop", 1)),
dbObj ("$group", dbObj (
"_id", "$_id.state",
"biggestCity", dbObj ("$last", "$_id.city"),
"biggestPop", dbObj ("$last", "$pop"),
"smallestCity", dbObj ("$first", "$_id.city"),
"smallestPop", dbObj ("$first", "$pop")
)),
dbObj ("$project", dbObj (
"_id", 0,
"state", "$_id",
"biggestCity", dbObj ("name", "$biggestCity", "pop", "$biggestPop"),
"smallestCity", dbObj ("name", "$smallestCity", "pop", "$smallestPop")
))
);
// Run aggregation query
DBCollection collection = mongoTemplate.getCollection(COLLECTION_NAME);
AggregationOutput output = collection.aggregate (aggregation);
Doing it this way, if it works in your editor (e.g. RoboMongo) it will work in your Java code although you will have to manually convert the objects from the result, which isn't too painful i.e.
List<MyResultClass> results = new ArrayList<MyResultClass>();
Iterator<DBObject> it = output.results().iterator();
while (it.hasNext()) {
DBObject obj = it.next();
MyResultClass result = mongoTemplate.getConverter().read(MyResultClass.class, obj);
results.add(result);
}
However, you may find the Spring Data Aggregation stuff does work OK for you. I love Spring and I do use Mongo Spring Data in various parts of my code, it is the aggregation support that lets it down e.g. doing a "$push" inside a "$group" with multiple items doesn't seem to work. I'm sure it will improve with time (and better documentation). Other people have echoed these thoughts e.g. http://movingfulcrum.tumblr.com/post/61693014502/spring-data-and-mongodb-a-mismatch-made-in-hell - see section 4.
Happy coding!

Updating inner doc from mongo

This is my sample doc.
{
"_id" : ObjectId("51f20148a85e39af87510305"),
"group_name" : "sai",
"privileges" : [
"Notification",
"News Letter"
],
"users" : [
{
"full_name" : "sumit",
"user_name" : "sumitdesh",
"password" : "magicmoments",
"status" : "Active"
},
{
"full_name" : "ad",
"user_name" : "asd",
"password" : "asdf",
"status" : "Active"
}
]
}
I want to replace inner doc from users array with a new doc.
This is my java code:
BasicDBObject g1=new BasicDBObject();
g1.put("full_name", "ram");
g1.put("user_name", "ram123");
g1.put("password", "pass$123");
g1.put("status", "Inactive");
BasicDBObject doc=new BasicDBObject();
doc.put("users",g1);
BasicDBObject q=new BasicDBObject("users.user_name","asd");
con.update(q,doc);
Any help is appreciated
Expected output is as follows
I want to replace inner doc with these values
{
"_id" : ObjectId("51f20148a85e39af87510305"),
"group_name" : "sai",
"privileges" : [
"Notification",
"News Letter"
],
"users" : [
{
"full_name" : "sumit",
"user_name" : "sumitdesh",
"password" : "magicmoments",
"status" : "Active"
},
{
"full_name" : "ram",
"user_name" : "ram123",
"password" : "pass$123",
"status" : "Inactive"
}
]
}

I must combine $set and $ operators, then you can update an specific item of array.
BasicDBObject g1 = new BasicDBObject();
g1.put("users.$.full_name", "ram");
g1.put("users.$.user_name", "ram123");
g1.put("users.$.password", "pass$123");
g1.put("users.$.status", "Inactive");
BasicDBObject doc = new BasicDBObject();
doc.put("$set", g1);
BasicDBObject q = new BasicDBObject("users.user_name","asd");
con.update(q,doc);

Your code will create a new document consisting only of the new user. To add a new element to an array in an existing document, use the $push operator
BasicDBObject where = new BasicDBObject("_id", new ObjectId("51f20148a85e39af87510305");
BasicDBObject doc = //... your new user object
BasicDBObject push = new BasicDBObject("$push", doc);
con.update(where, push);
To modify a field of an existing document, you can use the set-operator combined with the $-placeholder. This changes the user_name from "foo" to "bar"
BasicDBObject where = new BasicDBObject("users.user_name", "foo");
BasicDBObject value = new BasicDBObject("users.$.user_name", "bar");
BasicDBObject set = new BasicDBObject("$set", value);
con.update(where, set);
But the least headache-inducing way is to just keep the whole DBObject around when you retrieve an object from the database, mirror all modifications in the DBObject, and then call
con.save(dbObject);
An ORM wrapper library can do this for you. But while it is the easiest way, it isn't the most efficient way, because the whole document will be sent to the database. This is a problem which can be easily filed under "premature optimization" when writes are infrequent and the documents are small, but when you save often and have huge documents, it can become an issue.

This is actually fairly simple, if you follow the documentation.
The first difficulty is finding the document to update. You're looking for the user whose user_name field is 'asd', which is done, rather neatly, through the following query:
{'users.user_name': 'asd'}
The field name needs to be escaped in the mongo shell (it's a compound name) but you need not worry about that in Java.
Now that you've found your user, you need to change it. MongoDB magically stores the matched array index as $, which allows you to write the update criteria as:
{
$set: {
'users.$': {
full_name: 'ram',
user_name: 'ram123',
password: 'pass$123',
status: 'inactive'
}
}
}
You obviously know your way around the Java connector, I'll leave the transformation of my JSON object to instances of BasicDBObject to you.

How to query whole word in Java MongoDB

I'm using Java Mongo DB driver.
Im doing some OR and AND operation to query the collection.
QueryObj = new BasicDBObject("key1",Pattern.compile("v",Pattern.CASE_INSENSITIVE));
QueryList.add(QueryObj);
DBObject OrQuery = new BasicDBObject("$or", QueryList);
DBCursor cursor = MyCollection.find(OrQuery);
my Sample collection have 4 rows(JSON format might be wrong)
{
"key1": ["val1","val3"]
},
{
"key1": ["val2","val3"]
},
{
"key1": ["val3"]
},
{
"key1": ["val1","val2"]
}
If i search for "val2"
QueryObj = new BasicDBObject("key1",Pattern.compile("val2",Pattern.CASE_INSENSITIVE));
i'm getting expected output 2nd and 4th row
{
"key1": ["val2","val3"]
},
{
"key1": ["val1","val2"]
}
if i search just "v"
QueryObj = new BasicDBObject("key1",Pattern.compile("v",Pattern.CASE_INSENSITIVE));
i should get null set, but getting all the 4 rows, though the array have a character "v".
i need to search the whole word.

Do you mean that you want to search for the complete word 'v' -- in which case, I believe your pattern would be as follows where ^ denote the start of word and $ denote the end of word.
QueryObj = new BasicDBObject("key1",Pattern.compile("^v$",Pattern.CASE_INSENSITIVE));
Regards,
Kay

I hope it should help you
values ="val1";
CMD we use in DB as :
db.collection_name.findOne({ key1: "val1"})
Likewise use
query.put("key1", values)
Use the findOne() instead of find() in the statement
Correct me if 'm wrong

If you have the 4 documents above you can just use the following query to retrieve only the ones you need:
db.collection.find({"key1": "val2"})
This returns:
{ "_id" : ObjectId("507587fdf1ab6b3d9e0151d3"), "key1" : [ "val2", "val3" ] }
{ "_id" : ObjectId("50758801f1ab6b3d9e0151d5"), "key1" : [ "val1", "val2" ] }
(assuming your collection is called 'collection').
In the Java Driver the correct call should be:
Mongo mongo = new Mongo("localhost", 27017);
DB db = mongo.getDB("test");
BasicDBObject query = new BasicDBObject("key1", "val2");
db.getCollection("collection").find(query);
//omitting try catch
If I understand your question correct, you don't need to use a Pattern here.
hope this helps