1. Scala with MongoDB
Abdhesh Kumar
Email: abdhesh@knoldus.com
Twitter:@abdheshkumar90

2. 1. What is MongoDB?
2. Why we use MongoDB?
3. What are the MongoDB Terminologies?
4. How to Install and Use MonogDB?
5. What are the Operators of MongoDB?
6. What is Casbah?
7. What is Salat?
Agenda

3. What is MongoDB?
➢ MongoDB is a document-oriented database management
system designed for performance, horizontal scalability, high
availability,open source NoSQL database(Schemaless or Non-
relational) ,And advanced queryability.
➢ MongoDB is a document-based database system, and as a
result, all records, or data, in MongoDB are documents.

4. Why we use MongoDB?
Document Oriented
➢ Documents (objects) map nicely to programming language data
types.
➢ Dynamically-typed (schemaless) for easy schema evolution.
➢ No joins and no transactions for high performance and easy
scalability
High Performance
➢ No joins and no transactions makes reads and writes fast
➢ Indexes can include keys from embedded documents and
arrays.
➢ Optional asynchronous writes
.

5. High Availability
➢Replicated servers with automatic master failover.
Easy Scalability
➢ Automatic sharding distributes collection data across machines.
➢Reads and writes are distributed over shards
Flexibility
➢MongoDB stores data in JSON documents (which we serialize
to BSON).

6. Indexing
➢ MongoDB supports generic secondary indexes, allowing a
variety of fast queries,and provides unique, compound, and
geospatial indexing capabilities as well.
Fixed-size collections
➢ Capped collections are fixed in size and are useful for certain
types of data, such as logs.
➢ Real time aggregation
➢ Rich query capabilities
➢ Geospatial features
➢ Flexible schema

7. MongoDB Terminologies
Sql Terms/Concepts MongoDB Terms/Concepts
database database
table collection
index index
row Document or *BSON document
column Field or BSON field
join *Embedding and linking
Primary key _id
Group by aggregation

8. MongoDB Terms/Concepts
Documents:
➢ The concept of a document: an ordered set of keys with
associated values.
➢ documents are represented as objects:
{"greeting" : "Hello, world!"}
Collections:
➢ A collection is a group of documents.

9. Embedding:
➢ “Embedding is the nesting of objects and arrays inside a
BSON document”
Linking:
➢ “Links are references between documents”
Aggregation:
➢ The MongoDB aggregation framework provides a means to
calculate aggregated values without having to use map-reduce.
➢ If you’re familiar with SQL, the aggregation framework
provides similar functionality to GROUP BY and related SQL
operators as well as simple forms of “self joins.” Additionally,
the aggregation framework provides projection capabilities to
reshape the returned data.

10. What is JSON?
➢ JSON (JavaScript Object Notation) is a lightweight data-
interchange format.
➢ JSON is built on two structures:
1. A collection of name/value pairs. ex.object, record, struct,
dictionary, hash table, keyed list, or associative array
2. An ordered list of values. ex. array, vector, list, or sequence

11. {
"_id" : 1,
"name" : { "first" : "Rohan", "last" : "Singh" },
"contributes" : [ "TypeSafe", "Knoldus" ],
"awards" : [
{
"award" : "Play Framework Expert",
"year" : 2012,
"by" : "TypeSafe"
},
{ "award" : "Scala Expert",
"year" : 2013,
"by" : "Knoldus"
}
]
}

12. What is BSON?
➢ BSON is a binary-encoded serialization of JSON-like
document.
➢ BSON supports the embedding of documents and arrays
within other documents and arrays.
➢ MongoDB uses BSON as the data storage and network
transfer format for “documets”.

13. Install MongoDB
$ wget http://downloads.mongodb.org/osx/mongodb-osx-x86_64-
2.0.6.tgz
$ tar -zxvf mongodb-osx-x86_64-2.0.6.tgz
$ sudo mkdir -p /data/db
$ sudo chown `id -u` /data/db

14. Starting MonDB and Mongo Shell
➢ $ ./bin/mongod
➢ $ mongo
MongoDB shell version: 2.4.1
connecting to: test
>

15. MongoDB Operators
Query Selectors:
➢ Comparison
$all, $gt, $gte, $in, $lt, $lte, $ne, $nin
➢ Logical
$and, $or, $nor, $not
➢ Element
$exists, $mod, $type
➢ JavaScript
$regix, $where

16. ➢ Array
$elemMatch,$size
Update
➢ Fields
$inc, $set, $unset
➢ Array
$, $addToSet, $pop, $pullAll, $pull, $pushAll, $push
Projection
$, $elemMatch, $slice

17. What is the Casbah?
➢ Casbah is a Scala toolkit for MongoDB—We use the term “toolkit” rather
than “driver”, as Casbah integrates a layer on top of the official mongo-java-
driver for better integration with Scala.

18. Installing & Setting up Casbah
*You should have MongoDB setup and running on your machine.
Add casbah dependencies to buid.sbt
resolvers += "Scala-tools" at
"https://oss.sonatype.org/content/groups/scala-tools"
resolvers += "Sonatype Snapshot" at
"https://oss.sonatype.org/content/repositories/releases"
libraryDependencies ++= Seq(
"org.mongodb" % "casbah_2.10" % "2.5.1"
)

19. Use Casbah with Scala
➢ Import the Driver
import com.mongodb.casbah.Imports._
➢ Connecting to MongoDB
Connect to default - localhost, 27017
val mongoConnection = MongoConnection()
connect to "mongodb01" host, default port
val mongoConnection = MongoConnection("mongodb01")
connect to "mongodb02" host, port 42017
val mongoConnection = MongoConnection("mongodb02", 42017)

20. val mongoDB = mongoConnection("casbah_test")
Connect casbah_test database with test_data collecion by chaining
val mongoColl = mongoConnection("casbah_test")("test_data")
Working with Collections

21. What is Salat?
➢ Salat is a bi-directional Scala case class serialization library.
➢ Salat provides fast, reliable bi-directional serialization between
Scala case classes and MongoDB's DBObject format.
➢ case classes can be used directly for storing document by
simply declaring a DAO and with the help of some annotations

22. Salat DAO
SalatDAOmakes it simple to start working with your case class objects.
Use it as is or as the basis for your own DAO implementation.
By extending SalatDAO, you can do the following out of box:
➢ insert and get back an Option with the id
➢ findOne and get back an Option
➢ typed to your case class
➢ find and get back a Mongo cursor typed to your class
➢ iterate, limit, skip and sort
➢ update with a query and a case class
➢ save and remove case classes
➢ Projections
➢ built-in support for child collections

23. What Scala types can Salat handle?
➢ case classes
➢ embedded case classes
➢ embedded case classes typed to a trait or abstract superclass annotated
with @Salat
➢ Scala enums
➢ Options
➢ Collections
Collections
➢ Maps are represented as DBObject ; all other collections turn into DBList .

24. Salat collection support
Salat 0.0.8-SNAPSHOT and above support the following mutable and
immutable collections:
➢ Map
➢ Lists and linked lists
➢ Seqs and indexed seqs
➢ Set
➢ Buffer
➢ Vector

25. Salat Unsupported types
Salat can't support any of these types right now:
➢ Nested inner classes
➢ A class typed at the top-level to a trait or an abstract superclass
Salat can't support these types because the mongo-java-driver doesn't support
Them:
➢ Any type of Map whose key is not a String
➢ any type of map whose key is a String containing . or $

26. Salat Supports Annotations
Salat offers the following annotations to customize serialization
behavior:
➢ @Salat to support polymorphic instances of a trait or abstract
superclass
➢ @Key to change the name of a field
➢ @Persist to serialize a value outside the case class constructor
➢ @Ignore to ignore a field in the case class constructor
➢ @EnumAs to customize the behavior of a particular enum

27. Salat Grater
Grater
Salat as the notion of Grater that is responsible to the de/serialization
of a case class.
This through two simple functions, let have a Grater for the type T:
➢ asDBObject(t:T) : returns a MongoDB representation of t
➢ asObject(dbo:DBObject)[T] : returns a T instance based on the
provided
Mo ngoDB content

28. Installing & Setting up Salat
Add salat dependencies to buid.sbt
resolvers += "Novus Release Repository" at "http://repo.novus.com/releases/"
resolvers += "Sonatype OSS Snapshots" at "
https://oss.sonatype.org/content/repositories/snapshots"
libraryDependencies ++= Seq(
"com.novus" %% "salat" % "1.9.2-SNAPSHOT"
)

29. References
http://docs.mongodb.org/manual/