{
    "_id" : "rsStat",
    "version" : 3,
    "members" : [
        {
            "_id" : 0,
            "host" : "someDNS:27024",
            "priority" : 2
        },
        {
            "_id" : 1,
            "host" : "someDNS:27025",
            "priority" : 0,
            "slaveDelay" : 60
        }
    ]
}

Morphia morphia = new Morphia();
String host = "someDNS";
int port = 27024;
String dbName = "someDatabaseName";

// Configure the mongo options
MongoOptions options = new MongoOptions();
options.autoConnectRetry = true;
options.connectionsPerHost = 100;
options.w = WriteConcern.NONE.getW();
options.readPreference = ReadPreference.secondaryPreferred();
// options.slaveOk = true;

// Declare the real Mongo object
Mongo mongo;

// Look at the system.replset collection to know the replica set status
Mongo mongoInit = new Mongo(new ServerAddress(host, port), options);
DB localDb = mongoInit.getDB("local");
DBCollection replsetCollection = localDb.getCollection("system.replset");
DBObject replsetInfos = replsetCollection.findOne();

// If the returned object is null, there is no replica set (a single node)
if (replsetInfos == null)
{
	mongo = new Mongo(new ServerAddress(host, port), options);
}
else
{
	// It's a replica set, gather information of each node
	List<ServerAddress> addresses = getReplicaSetInfos(host, replsetInfos);

	// The Mongo constructor doesn't work with a list of only one address...
	if (addresses.size() > 1)
	{
		mongo = new Mongo(addresses, options);
	}
	else
	{
		mongo = new Mongo(addresses.get(0), options);
	}
}

// Create the morphia datastore
Datastore datastore = morphia.createDatastore(mongo, dbName);
datastore.getMongo().setReadPreference(ReadPreference.secondaryPreferred());

morphia.mapPackage("some.package");

datastore.ensureIndexes();

List<SomeDocument> docs = datastore.find(SomeDocument.class).queryNonPrimary().asList();