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  • Upgrade Considerations

Upgrading to the 4.0 Driver

Upgrading from the 3.12 Java driver

The 4.0 release is a major release as per the definition of semantic versioning. As such, users that upgrade to this release should expect breaking changes. That said, we have attempted to ensure that the upgrade process is as seamless as possible. Breaking changes are as follows:

  • Numerous classes and methods have been removed from the driver. All of these API elements are annotated as deprecated in the 3.12 release, so if you compile your application with 3.12 and enable deprecation warnings in the compiler, you will be able to locate all uses of these API elements and follow the recommendations contained in the Javadoc for each API element to remove usage from your application. Most of these API elements are unlikely to be used by normal applications, but one bears mentioning explicitly: the entire callback-based asynchronous driver has been removed. Applications relying on this driver must either port their application to the Reactive Streams driver, or else must remain on a 3.x driver release.
  • While the com.mongodb.MongoClient#getDB method is deprecated in 3.x drivers, it has not been removed in this release. It will remain at least until the next major release cycle.
  • The insert helper methods now return an insert result object instead of void.
  • The various toJson methods on BsonDocument, Document, and DBObject now return “relaxed” JSON instead of “strict” JSON. This creates more readable JSON documents at the cost of a loss of some BSON type information (e.g., differentiating between 32 and 64 bit integers).
  • The default BSON representation of java.util.UUID values has changed from JAVA_LEGACY to UNSPECIFIED. Applications that store or retrieve UUID values must explicitly specify which representation to use, via the uuidRepresentation property of MongoClientSettings (or MongoClientOptions for the legacy driver).
  • The connection pool no longer enforces any restrictions on the size of the wait queue of threads or asynchronous tasks that require a connection to MongoDB. It is up to the application to throttle requests sufficiently rather than rely on the driver to throw a MongoWaitQueueFullException.
  • The driver no longer logs via JUL (java.util.logging). The only supported logging framework is SLF4J.
  • The embedded and Android drivers have been removed. Applications relying on these drivers must remain on a 3.x driver release.
  • The mongo-java-driver and mongodb-driver “uber-jars” are no longer published. Applications that reference either of these artifacts must switch to either mongodb-driver-sync or mongodb-driver-legacy, depending on which API is being used. Care should be taken to ensure that neither of the uber-jars are included via a transitive dependency, as that could introduce versioning conflicts.
  • Java 8 is now the minimum supported version. Applications using older versions of Java must remain on a 3.x driver release.
  • Several binary compatibility breaks were introduced (in particular, the change to the signature of the insert helper methods), so any classes that link to the driver must be recompiled in order to work with this release.

Upgrading from the 1.12 Reactive Streams driver

The main change to the MongoDB Reactive Streams Java Driver 1.12 driver is the removal of the Success type.

Breaking changes are as follows:

  • Publisher<Success> has been migrated to Publisher<Void>. Please note that onNext will not be called just onComplete if the operation is successful or onError if there is an error.
  • Removal of deprecated methods

Upgrading from the 2.8 Scala driver

As the mongodb-driver-async package was deprecated in 3.x. The 4.0 version of the MongoDB Scala Driver is now built upon the mongo-java-driver-reactivestreams 4.0 driver. One major benefit is now the Scala driver is also a reactive streams driver.

Breaking changes are as follows:

  • Observable is now a reactive streams Publisher implementations Observable implicits extend any Publisher implementation and can be imported from org.mongodb.scala._
  • Completed type has now been removed. Observable[Completed] has been migrated to Observable[Void]. Please note that onNext will not be called just onComplete if the operation is successful or onError if there is an error.
  • Removal of deprecated methods

System Requirements

The minimum JVM is Java 8.


The following table specifies the compatibility of the MongoDB Java driver for use with a specific version of MongoDB.

Java Driver Version MongoDB 3.0 MongoDB 3.2 MongoDB 3.4 MongoDB 3.6 MongoDB 4.0 MongoDB 4.2 MongoDB 4.4
Version 4.0
Version 3.12 ✓*
Version 3.11
Version 3.10
Version 3.9
Version 3.9
Version 3.8
Version 3.7
Version 3.6
Version 3.5
Version 3.4
Version 3.3
Version 3.2
Version 3.1
Version 3.0

* The 3.12 driver is tested against MongoDB 4.4 but does not support all the new features