MongoDB Extended JSON

The Scala driver supports reading and writing BSON documents represented as
MongoDB Extended JSON. Both variants are supported:

• Strict Mode: representations of BSON types that conform to the JSON RFC. This is the format that mongoexport produces and mongoimport consumes.
• Shell Mode: a superset of JSON that the MongoDB shell can parse.

Furthermore, the Document provides two sets of convenience methods for this purpose:

• Document.toJson(): a set of overloaded methods that convert a Document instance to a JSON string
• Document(json): a set of overloaded static factory methods that convert a JSON string to a Document instance

Writing JSON

Consider the task of implementing a mongoexport-like tool using the Scala driver.

val fileName =    // initialize to the path of the file to write to
val collection =  // initialize the collection from which you want to query

val writer: PrintWriter = new PrintWriter(fileName)
collection.find().subscribe(
      (doc: Document) => output.write(s"${doc.toJson}\r\n"),
      (t: Throwable) => // handle failure,
      () => output.close())

The Document.toJson() method constructs an instance of a JsonWriter with its default settings, which will write in strict mode with no new lines or indentation.

You can override this default behavior by using one of the overloads of toJson(). As an example, consider the task of writing a JSON string that can be copied and pasted into the MongoDB shell:

import java.text.SimpleDateFormat

val fmt = new SimpleDateFormat("dd/MM/yy")
val first = fmt.parse("01/01/2014")
val second = fmt.parse("01/01/2015")
val doc = Document("startDate" -> Document("$gt" -> first, "$lt" -> second))
println(doc.toJson(new JsonWriterSettings(JsonMode.SHELL)))

This code snippet will print out MongoDB shell-compatible JSON, which can then be pasted into the shell:

{ "startDate" : { "$gt" : ISODate("2014-01-01T05:00:00.000Z"), "$lt" : ISODate("2015-01-01T05:00:00.000Z") } }

Reading JSON

Consider the task of implementing a mongoimport-like tool using the Java driver.

import scala.io.Source
val fileName =    // initialize to the path of the file to read from
val collection =  // initialize the collection from which you want to import to

try {
  for (json <- Source.fromFile(fileName).getLines()) {
    collection.insertOne(Document(json)).head()
  }
} catch {
  case ex: Exception => println("Bummer, an exception happened.")
}

The Document(json) companion helper method constructs an instance of a JsonReader with the given string and returns an instance of an equivalent Document instance. JsonReader automatically detects the JSON flavor in the string, so you do not need to specify it.