Admin Quick Tour

This is the second part of the MongoDB driver quick tour. In the quick tour we looked at how to use the Reactive Streams Java driver to execute basic CRUD operations. In this section we’ll look at some of the administrative features available in the driver.

The following code snippets come from the example code that can be found with the driver source.


See the installation guide for instructions on how to install the MongoDB Driver.


To get started we’ll quickly connect and create a mongoClient, database and collection variable for use in the examples below:

MongoClient mongoClient = new MongoClient(new ConnectionString("mongodb://localhost"));
MongoDatabase database = mongoClient.getDatabase("mydb");
MongoCollection<Document> collection = database.getCollection("test");


Calling the getDatabase() on MongoClient does not create a database. Only when a database is written to will a database be created. Examples include the creation of an index or the insertion of a document into a previously non-existent collection.

Get A List of Databases

You can get a list of the available databases by calling the listDatabaseNames method. Here we use the static printSubscriber helper so that we can print the list of database names:

mongoClient.listDatabaseNames().subscribe(printSubscriber("Database Names: "));

Drop A Database

You can drop a database by name using a MongoClient instance. Here we block for the Observable to complete before continuing.


Create A Collection

Collections in MongoDB are created automatically simply by inserted a document into it. Using the createCollection method, you can also create a collection explicitly in order to customize its configuration. For example, to create a capped collection sized to 1 megabyte:

database.createCollection("cappedCollection", new CreateCollectionOptions().capped(true).sizeInBytes(0x100000))
    .subscribe(printSubscriber("Creation Created!"));

Get A List of Collections

You can get a list of the available collections in a database:

database.listCollectionNames().subscribe(printSubscriber("Collection Names: %s"));

Drop A Collection

You can drop a collection by using the drop() method:


Create An Index

MongoDB supports secondary indexes. To create an index, you just specify the field or combination of fields, and for each field specify the direction of the index for that field. For 1 ascending or -1 for descending. The following creates an ascending index on the i field:

// create an ascending index on the "i" field
collection.createIndex(new Document("i", 1)).subscribe(printSubscriber("Created an index named: "));

Get a List of Indexes on a Collection

Use the listIndexes() method to get a list of indexes. The following uses the PrintDocumentSubscriber to print the json version of each index document:


The example should print the following indexes:

{ "v" : 1, "key" : { "_id" : 1 }, "name" : "_id_", "ns" : "mydb.test" }
{ "v" : 1, "key" : { "i" : 1 }, "name" : "i_1", "ns" : "mydb.test" }

Text indexes

MongoDB also provides text indexes to support text search of string content. Text indexes can include any field whose value is a string or an array of string elements. To create a text index specify the string literal “text” in the index document:

// create a text index on the "content" field
subscriber = printSubscriber("Created an index named: ");
collection.createIndex(new Document("content", "text")).subscribe(subscriber);

As of MongoDB 2.6, text indexes are now integrated into the main query language and enabled by default (here we use the Filters.text helper):

// Insert some documents
subscriber = new TestSubscriber();
collection.insertMany(asList(new Document("_id", 0).append("content", "textual content"),
        new Document("_id", 1).append("content", "additional content"),
        new Document("_id", 2).append("content", "irrelevant content"))).subscribe(subscriber);

// Find using the text index
subscriber = printSubscriber("Text search matches: ");
collection.count(text("textual content -irrelevant")).subscribe(subscriber);

// Find using the $language operator
subscriber = printSubscriber("Text search matches (english): ");
Bson textSearch = text("textual content -irrelevant", new TextSearchOptions().language("english"));

// Find the highest scoring match
System.out.print("Highest scoring document: ");
Document projection = new Document("score", new Document("$meta", "textScore"));

and it should print:

Text search matches: [2]
Text search matches (english): [2]
Highest scoring document: { "_id" : 1, "content" : "additional content", "score" : 0.75 }

For more information about text search see the text index and $text query operator documentation.

Running a command

While not all commands have a specific helper, however you can run any command by using the runCommand() method. Here we call the buildInfo command:

database.runCommand(new Document("buildInfo", 1)).subscribe(printDocumentSubscriber());