#Connect dropwizard to MongoDB

dropwizard-mongo is a set of factories and health checks to be used with dropwizard for connecting to MongoDB.

Disclaimer

Update 8/1: Major refactor that simplifies usage. Thanks to kgilmer for the review.
This project is brand new, so I have a lot of additional work to support the multiple options that can be passed to the MongoClient, DB, and DBCollection objects.

##Usage

Installation

The project artifacts are not currently hosted in a maven repository, so you will need to clone the repo and build the dropwizard-mongo project at a minimum.

I recommend you use dropwizard-mongo in combination with the MongoJack project for quickest implementation. The dropwizard-mongo-example project shows an example of using MongoJack with dropwizard-mongo.

Updating Your yaml

If you want the factory to build a MongoClient object you can specify the connections in you config file.

mongoDB:
  connections:
    - host: localhost
      port: 27017
    - host: 192.168.1.12
      port: 27017

If you want to the factory to build a DB object you will need to further specify the db name in the config.

mongoDB:
    dbName: unittest
    connections:
        - host: localhost
          port: 27017
        - host: 192.168.1.12
          port: 27017

Finally, the factory can return a DBCollection object you will need to further specify the collection name in the config.

mongoDB:
    dbName: unittest
    collName: test
    connections:
        - host: localhost
          port: 27017
        - host: 192.168.1.12
          port: 27017

Updating you configuration

You will need to add a reference to MongoFactory in your class that extends Configuration or you can extend from com.eeb.dropwizardmongo.configuration.DropwizardMongoConfiguration.

@Valid
@NotNull
private MongoFactory mongoFactory = new MongoFactory();
  
@JsonProperty("mongoDB")
public MongoFactory getMongoFactory() {
    return this.mongoFactory;
}
  
@JsonProperty("mongoDB")
public void setMongoFactory(MongoFactory MongoFactory) {
    this.mongoFactory = MongoFactory;
}         

Update your applications run method

Your class that extends from Application needs to be updated to register the health checks and call the factory method you wish to use. Once you have the object you want you can pass it to your dropwizard resources.

Registering the health checks

 final MongoClient mongoClient = config.getMongoFactory().buildClient(environment);
 environment.healthChecks().register("mongo",new MongoHealthCheck(mongoClient));

Building a MongoClient object

 final MongoClient mongoClient = config.getMongoFactory().buildClient(environment); 
 //Register Resources
 environment.jersey().register(new CollectionIdsResource(mongoClient));

Building a DB object

 final DB db = config.getMongoFactory().buildDB(environment); 
 //Register Resources
 environment.jersey().register(new CollectionIdsResource(db));

Building a DBCollection object

final DBCollection coll = config.getMongoFactory().buildColl(environment); 
//Register Resources
environment.jersey().register(new CollectionIdsResource(coll));

Using MongoJack with dropwizard-mongo

The secret sauce here is MongoJack. It lets me pass my Jackson API objects directly to the MongoDB API as well as returning the results of queries as my API objects.

Super basic API object representing a MongoDB document:

public class MongoDocument {

    private String id;

    @ObjectId
    @JsonProperty("_id")
    public String getId() {
        return this.id;
    }

    @ObjectId
    @JsonProperty("_id")
    public void setId(String id) {
        this.id = id;
    }

}

My Resource's GET handler.

@GET
public List<MongoDocument> fetch(@PathParam("collection") String collection) {
   
    JacksonDBCollection<MongoDocument, String> coll = JacksonDBCollection.wrap(mongoDB.getCollection(collection), MongoDocument.class,
            String.class);
    DBCursor<MongoDocument> cursor = coll.find();
   
    List<MongoDocument> l = new ArrayList<>();

    try {
        while(cursor.hasNext()) {
            l.add(cursor.next());
        }
    }finally {
        cursor.close();
    }

    return l;
}

MongoJack provides wrappers for the standard MongoDB api calls that will parse MongoDB documents into objects that are Jackson annotated.