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Write Operations

On this page

  • Prerequisites
  • Connect to a MongoDB Deployment
  • Insert a Document
  • Insert Multiple Documents
  • Update Existing Documents
  • Filters
  • Update Operators
  • Update a Single Document
  • Update Multiple Documents
  • Update Options
  • Replace an Existing Document
  • Filters
  • Replace a Document
  • Update Options
  • Delete Documents
  • Filters
  • Delete a Single Document
  • Delete Multiple Documents
  • Write Concern

You can perform write operations to insert new documents, update existing documents, replace an existing document, or delete existing documents from a collection.

Prerequisites

You must set up the following components to run the code examples in this guide:

  • A test.restaurants collection populated with documents from the restaurants.json file in the documentation assets GitHub.

  • The following import statements:

import org.mongodb.scala._
import org.mongodb.scala.model._
import org.mongodb.scala.model.Filters._
import org.mongodb.scala.model.Updates._
import org.mongodb.scala.model.UpdateOptions
import org.mongodb.scala.bson.BsonObjectId

Note

This guide uses the Observable implicits as covered in the Quick Start Primer.

Connect to a MongoDB Deployment

First, connect to a MongoDB deployment, then declare and define MongoDatabase and MongoCollection instances.

The following code connects to a standalone MongoDB deployment running on localhost on port 27017. Then, it defines the database variable to refer to the test database and the collection variable to refer to the restaurants collection:

val mongoClient: MongoClient = MongoClient()
val database: MongoDatabase = mongoClient.getDatabase("test")
val collection: MongoCollection[Document] = database.getCollection("restaurants")

To learn more about connecting to MongoDB deployments, see the Connect to MongoDB tutorial.

Insert a Document

To insert a single document into the collection, you can use the collection's insertOne() method:

val document = Document("name" -> "Café Con Leche" ,
                        "contact" -> Document("phone" -> "228-555-0149",
                                              "email" -> "cafeconleche@example.com",
                                              "location" -> Seq(-73.92502, 40.8279556)),
                        "stars" -> 3, "categories" -> Seq("Bakery", "Coffee", "Pastries"))
collection.insertOne(document).printResults()

Note

If no top-level _id field is specified in the document, MongoDB automatically generates a value and adds this field to the inserted document.

Insert Multiple Documents

To insert multiple documents, you can use the collection's insertMany() method, which takes a list of documents to insert as a parameter.

The following example inserts two documents into the collection:

val doc1 = Document("name" -> "Amarcord Pizzeria" ,
                    "contact" -> Document("phone" -> "264-555-0193",
                                          "email" -> "amarcord.pizzeria@example.net",
                                          "location" -> Seq(-73.88502, 40.749556)),
                    "stars" -> 2, "categories" -> Seq("Pizzeria", "Italian", "Pasta"))
val doc2 = Document("name" -> "Blue Coffee Bar" ,
                    "contact" -> Document("phone" -> "604-555-0102",
                                          "email" -> "bluecoffeebar@example.com",
                                          "location" -> Seq(-73.97902, 40.8479556)),
                    "stars" -> 5, "categories" -> Seq("Coffee", "Pastries"))
collection.insertMany(Seq(doc1, doc2)).printResults()

Note

If no top-level _id field is specified in the document, MongoDB automatically generates a value and adds this field to the inserted document.

Update Existing Documents

To update existing documents in a collection, you can use the collection's updateOne() or updateMany() methods.

Filters

You can pass in a filter document to the methods to specify which documents to update. The filter document specification is the same as for read operations. To facilitate the creation of filter objects, the driver provides the Filters helper class.

To specify an empty filter and match all documents in a collection, use an empty Document object as the filter.

Update Operators

To change a field in a document, MongoDB provides update operators. To specify the modification to perform using the update operators, create an update document. To learn more about update operators, see Update Operators in the Server manual.

To facilitate the creation of update documents, the driver provides the Updates helper class. To learn more about using builders to specify updates, see the Updates guide.

Important

The _id field is immutable, so you cannot change the value of the _id field in a document.

Update a Single Document

The updateOne() method updates a single document, even if the filter condition matches multiple documents in the collection.

The following operation on the restaurants collection updates a document in which the value of the _id field is BsonObjectId("57506d62f57802807471dd41"):

collection.updateOne(
                equal("_id", BsonObjectId("57506d62f57802807471dd41")),
                combine(set("stars", 1), set("contact.phone", "228-555-9999"), currentDate("lastModified")))
          .printResults()

Specifically, the operation uses the following methods:

  • Updates.set() to set the value of the stars field to 1 and the contact.phone field to "228-555-9999"

  • Updates.currentDate() to modify the lastModified field to the current date. If the lastModified field does not exist, the operator adds the field to the document.

Update Multiple Documents

The updateMany() method updates all documents that match the filter condition.

The following operation on the restaurants collection updates all documents in which the value of the stars field is 2:

collection.updateMany(
              equal("stars", 2),
              combine(set("stars", 0), currentDate("lastModified")))
          .println()

Specifically, the operation uses the following methods:

  • Updates.set() to set the value of the stars field to 0

  • Updates.currentDate() to set the lastModified field to the current date. If the lastModified field does not exist, the operator adds the field to the document.

Update Options

When using the updateOne() and updateMany() methods, you can include an UpdateOptions document to specify the upsert option or the bypassDocumentationValidation option:

collection.updateOne(
                equal("_id", 1),
                combine(set("name", "Fresh Breads and Tulips"), currentDate("lastModified")),
                UpdateOptions().upsert(true).bypassDocumentValidation(true))
          .printResults()

Replace an Existing Document

To replace an existing document in a collection, you can use the collection's replaceOne() method.

Important

The _id field is immutable, so you cannot replace the _id field in a document.

Filters

You can pass in a filter document to the replaceOne() method to specify which document to replace. The filter document specification is the same as for read operations. To facilitate the creation of filter objects, the driver provides the Filters helper class.

To specify an empty filter and match all documents in a collection, use an empty Document object as the filter.

The replaceOne() method replaces at most a single document, even if the filter condition matches multiple documents in the collection.

Replace a Document

To replace a document, pass a new document to the replaceOne() method.

Important

The replacement document can have different fields from the original document. In the replacement document, you can omit the _id field since the _id field is immutable. However, if you do include the _id field, you cannot specify a different value for the _id field.

The following operation on the restaurants collection replaces the document in which the value of the _id field is BsonObjectId("57506d62f57802807471dd41"):

collection.replaceOne(
                equal("_id", BsonObjectId("57506d62f57802807471dd41")),
                Document("name" -> "Green Salads Buffet", "contact" -> "TBD",
                         "categories" -> Seq("Salads", "Health Foods", "Buffet")))
         .printResults()

Update Options

When using the replaceOne() method, you can include an UpdateOptions document to specify the upsert option or the bypassDocumentationValidation option:

collection.replaceOne(
                equal("name", "Orange Patisserie and Gelateria"),
                Document("stars" -> 5, "contact"  -> "TBD",
                         "categories" -> Seq("Cafe", "Pastries", "Ice Cream")),
                UpdateOptions().upsert(true).bypassDocumentValidation(true))
          .printResults()

Delete Documents

To delete documents in a collection, you can use the deleteOne() and deleteMany() methods.

Filters

You can pass in a filter document to the methods to specify which documents to delete. The filter document specification is the same as for read operations. To facilitate the creation of filter objects, the driver provides the Filters helper class.

To specify an empty filter and match all documents in a collection, use an empty Document object as the filter.

Delete a Single Document

The deleteOne() method deletes at most a single document, even if the filter condition matches multiple documents in the collection.

The following operation on the restaurants collection deletes a document in which the value of the _id field is ObjectId("57506d62f57802807471dd41"):

collection.deleteOne(equal("_id", new ObjectId("57506d62f57802807471dd41"))).subscribe(new ObservableSubscriber<DeleteResult>())

Delete Multiple Documents

The deleteMany() method deletes all documents that match the filter condition.

The following operation on the restaurants collection deletes all documents in which the value of the stars field is 4:

collection.deleteMany(equal("stars", 4)).printResults()

Write Concern

Write concern describes the level of acknowledgment requested from MongoDB for write operations.

You can configure a write concern at the following levels:

  • In a MongoClient in the following ways:

    • By creating a MongoClientSettings instance:

      val mongoClient: MongoClient = MongoClient(MongoClientSettings.builder()
                                                      .applyConnectionString(ConnectionString("mongodb://host1,host2"))
                                                      .writeConcern(WriteConcern.MAJORITY)
                                                      .build())

    • By creating a ConnectionString instance:

      val mongoClientt = MongoClient("mongodb://host1:27017,host2:27017/?w=majority")

  • In a MongoDatabase by using the withWriteConcern() method:

    val database = mongoClient.getDatabase("test").withWriteConcern(WriteConcern.MAJORITY)

  • In a MongoCollection by using the withWriteConcern() method:

    val collection = database.getCollection("restaurants").withWriteConcern(WriteConcern.MAJORITY)

MongoDatabase and MongoCollection instances are immutable. Calling withWriteConcern() on an existing MongoDatabase or MongoCollection instance returns a new instance and does not affect the instance on which the method is called.

In the following example, the collWithWriteConcern instance has the write concern of majority whereas the read preference of the collection is unaffected:

val collWithWriteConcern = collection.withWriteConcern(WriteConcern.MAJORITY)

You can build MongoClientSettings, MongoDatabase, or MongoCollection instances to include combinations of read concerns, read preferences, and write concerns.

For example, the following code sets all three at the collection level:

val collection = database.getCollection("restaurants")
                         .withReadPreference(ReadPreference.primary())
                         .withReadConcern(ReadConcern.MAJORITY)
                         .withWriteConcern(WriteConcern.MAJORITY)

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