Retrieve Data

Sample Data

The examples in this guide use the companies collection in the sample_training database from the Atlas sample datasets. To access this collection from your Scala application, create a MongoClient that connects to an Atlas cluster and assign the following value to your database and collection variables:

val database: MongoDatabase = mongoClient.getDatabase("sample_training")
val collection: MongoCollection[Document] = database.getCollection("companies")

To learn how to create a free MongoDB Atlas cluster and load the sample datasets, see the Get Started with Atlas guide.

Find Multiple Documents

To find multiple documents in a collection, pass a query filter to the find() method that specifies the criteria of the documents you want to retrieve.

The find() method returns an instance of FindObservable, which you can iterate to see the matching documents. Use the subscribe() method to iterate through the FindObservable.

The following example uses the find() method to find all documents in which the founded_year field has the value 1970 and prints the results:

val filter = equal("founded_year", 1970)
collection.find(filter).subscribe((doc: Document) => println(doc.toJson()),
                            (e: Throwable) => println(s"There was an error: $e"))

{"_id":{"$oid":"..."},"name":"Mitsubishi Motors","permalink":"mitsubishi-motors",
"crunchbase_url":"http://www.crunchbase.com/company/mitsubishi-motors",
... }
{"_id":{"$oid":"..."},"name":"Western Digital","permalink":"western-digital",
"crunchbase_url":"http://www.crunchbase.com/company/western-digital",
... }
{"_id":{"$oid":"..."},"name":"Celarayn","permalink":"celarayn","crunchbase_url":
"http://www.crunchbase.com/company/celarayn",
... }

collection.find()

Find One Document

To find a single document in a collection, call the find() method and pass a query filter that specifies the criteria of the document you want to find. Then, chain the first() method to find().

The find() method returns a FindObservable instance, and the first() method returns a SingleObserver instance that contains the first query result stored by the FindObservable. You can access the SingleObserver result by calling the subscribe() method.

The following example uses the find() and first() methods to find the first document in which the name field has the value "LinkedIn":

val filter = equal("name", "LinkedIn")
collection.find(filter).first().subscribe((doc: Document) => println(doc.toJson()),
                            (e: Throwable) => println(s"There was an error: $e"))

{"_id": {"$oid": "..."}, "name": "LinkedIn", "permalink": "linkedin", "crunchbase_url":
"http://www.crunchbase.com/company/linkedin", "homepage_url": "http://linkedin.com",
...}

Modify Find Behavior

You can modify the behavior of the find() method by chaining methods provided by the FindObservable class. The following table describes some of these methods:

The following example uses the find() method to find all documents in which the number_of_employees field has the value 1000. The example uses the limit() method to return a maximum of 5 results:

val filter = equal("number_of_employees", 1000)
collection.find(filter).limit(5).subscribe((doc: Document) => println(doc.toJson()),
                            (e: Throwable) => println(s"There was an error: $e"))

{"_id": {"$oid": "..."}, "name": "Akamai Technologies", "permalink": "akamai-technologies",
"crunchbase_url": "http://www.crunchbase.com/company/akamai-technologies", "homepage_url":
"http://www.akamai.com", ... }
{"_id": {"$oid": "..."}, "name": "Yodle", "permalink": "yodle", "crunchbase_url":
"http://www.crunchbase.com/company/yodle", "homepage_url": "http://www.yodle.com", ... }
{"_id": {"$oid": "..."}, "name": "Antal International", "permalink": "antal-international",
"crunchbase_url": "http://www.crunchbase.com/company/antal-international", "homepage_url":
"http://antal.com", ... }
{"_id": {"$oid": "..."}, "name": "Yatra online", "permalink": "yatra-online", "crunchbase_url":
"http://www.crunchbase.com/company/yatra-online", "homepage_url": "http://www.Yatra.com", ... }
{"_id": {"$oid": "..."}, "name": "Gumtree", "permalink": "gumtree", "crunchbase_url":
"http://www.crunchbase.com/company/gumtree", "homepage_url": "http://www.gumtree.co.za", ... }

For a full list of FindObservable member methods, see the API documentation for the FindObservable class.

API Documentation

To learn more about any of the methods discussed in this guide, see the following API documentation:

• find()

• first()

• limit()