Mapping to POJOs couldn't be easier!

Since MongoDB uses BSON, a binary form of JSON, to store its documents, a JSON mapper is a perfect mechanism for mapping Java objects to MongoDB documents. And the best Java JSON mapper is Jackson. Jackson's parsing/generating interface fits serialising to MongoDBs documents like a glove. Its plugins, custom creators, serialisers, views, pluggable annotators and so on give this mapping library a massive head start, making it powerful, performant, and robust.

Project documentation

The official documentation for this project lives here.

Mailing lists

The MongoDB Jackson Mapper users mailing list is hosted here.

Issues

The MongoDB Jackson Mapper issues are hosted here.

Quick start

Mongo driver compatibility

Version 2.3.0 and earlier are compatible only with the 2.x series mongo-java-driver.
Version 2.5.0 to 2.10.0 are compatible with the 3.x series mongodb-driver using the legacy 3.x series APIs.
Version 3.0.0 and later are compatible with versions 3.12.x and later of the mongo driver using mongodb-driver-sync without the legacy APIs.
Version 4.0.x is built on the mongojack-4.0.x branch against MongoDB's 4.0.x driver
Version 4.2.x is built on the master branch against MongoDB's 4.2.x driver
Version 4.3.x is built on the master branch against MongoDB's 4.3.x driver

Installation

Using a Java dependency manager

The quickest and easiest way to start using MongoJack is to use one of the standard Java build tools, such as Maven or Gradle. For example:

Maven:

<dependency>
  <groupId>org.mongojack</groupId>
  <artifactId>mongojack</artifactId>
  <version>4.2.0</version>
</dependency>

Gradle:

implementation 'org.mongojack:mongojack:4.2.0'

Writing code

Note: The 3.0 release of MongoJack removes all the functions of the older JacksonDBCollection, and all references to the legacy Mongo APIs.

MongoJack now supports only usage of the java mongo driver's 3.x API. There are two ways to use this feature.

Use the JacksonCodecRegistry class
Use the JacksonMongoCollection class

For a more detailed look at migration from 2.x to 3.x, see the migration guide

Using JacksonCodecRegistry

The java mongo 3.0 and higher driver supports the usage of codecs to map to specific types. MongoJack provides a Codec Registry which can be used for this purpose. Some example code making use of the JacksonCodecRegistry can be seen below:

MongoClient mongo = new MongoClient();
MongoDatabase mongoDatabase = mongo.getDatabase(testDatabaseName);
JacksonCodecRegistry jacksonCodecRegistry = new JacksonCodecRegistry();
jacksonCodecRegistry.addCodecForClass(MyObject.class);
MongoCollection<?> coll = mongoDatabase.getCollection("testCollection");
MongoCollection<MyObject> collection = coll.withDocumentClass(MyObject.class).withCodecRegistry(jacksonCodecRegistry);

The first two lines above get the database using the mongo driver. The third line constructs a new JacksonCodecRegistry. The fourth line tells the JacksonCodecRegistry to create a codec that will use Jackson for serialization/deserialization for the class MyObject. The fifth line gets a MongoCollection from the MongoDatabase, and the sixth tells the MongoCollection to use the MyObject class and work with the JacksonCodecRegsitry setup on lines three and four. JacksonCodecRegistry includes the default Mongo codecs, so it will also be capable of serializing and deserializing the Document and other default classes.

Using JacksonMongoCollection

JacksonMongoCollection is an implementation of MongoCollection which builds a JacksonCodecRegistry for you and adds some additional features such as mapping of queries and update documents. As an implementation of MongoCollection, it has all the features of the underlying driver, including map-reduce functionality, aggregation, transactions, etc. To use a JacksonMongoCollection the user will first need to initialize it using the builder.

MongoClient mongo = new MongoClient();
JacksonMongoCollection<MyObject> collection = JacksonMongoCollection.builder()
    .withObjectMapper(customObjectMapper)
    .build(mongo, "testDatabase", "testCollection", MyObject.class);

The builder allows you to specify the collection in a number of different ways; see the code and JavaDoc for specific options.

Usage largely follow the same pattern as the JacksonDBCollection with a few exceptions. In general, you use a JacksonMongoCollection as if it were a MongoCollection; it implements all methods and delegates almost everything to an underlying collection. The collection provides some additional helper methods, but in generally the interface is the same as com.mongodb.client.MongoCollection.

Old JacksonMongoCollection:

MockObject o1 = new MockObject("1", "ten", 10);
MockObject o2 = new MockObject("2", "ten", 10);
coll.insert(o1, o2, new MockObject("twenty", 20));
List<MockObject> results = collection.find(new BasicDBObject("string", "ten")).toArray();

New:

MockObject o1 = new MockObject("1", "ten", 10);
MockObject o2 = new MockObject("2", "ten", 10);
coll.insertMany(Arrays.asList(o1, o2, new MockObject("twenty", 20)));
List<MockObject> results = collection.find(Filters.eq("string", "ten")).into(new ArrayList<>());

The biggest difference between the usage of JacksonDBCollection and JacksonMongoCollection is that is that most of the inputs to the methods in the API must implement the org.bson.conversions.Bson interface. This allows you to pass instances of org.bson.Document, or com.mongodb.BasicDBObject, or any of Mongo's helper/builder objects like com.mongodb.client.model.Filters, com.mongodb.client.model.Aggregates, or com.mongodb.client.model.Updates.

MongoJack's older DBQuery, DBUpdate, and Aggregation helpers should all still work with the new JacksonMongoCollection, but they have been deprecated as the Mongo driver provides a set of useful builders for all of these things in the com.mongodb.client.model package. The implementation attempts to do mapping on any Bson inputs.

Using a custom ObjectMapper

If you want to use a custom ObjectMapper, you need to install MongoJackModule on your ObjectMapper before using it. This can be done with one of two mechanisms. The first one installs the MongoJackModule, and also installs JavaTimeModule and changes some other settings on the object mapper.

ObjectMapper customObjectMapper = new ObjectMapper()
// ... configure your object mapper
ObjectMapperConfigurer.configureObjectMapper(customObjectMapper)
// ...
MongoClient mongo = new MongoClient();
JacksonMongoCollection<MyObject> collection = JacksonMongoCollection.builder()
    .withObjectMapper(customObjectMapper)
    .build(mongo, "testDatabase", "testCollection", MyObject.class);

If you want to install only the module itself, you can use the following, which installs the module but makes no other changes:

ObjectMapper customObjectMapper = new ObjectMapper()
// ... configure your object mapper
ObjectMapperConfigurer.addMongojackModuleOnly(customObjectMapper)
// ...
MongoClient mongo = new MongoClient();
JacksonMongoCollection<MyObject> collection = JacksonMongoCollection.builder()
    .withObjectMapper(customObjectMapper)
    .build(mongo, "testDatabase", "testCollection", MyObject.class);

volomas / mongojack