30.2 MongoDB

MongoDB is an open-source NoSQL document database that uses a JSON-like schema instead of traditional table-based relational data. Spring Boot offers several conveniences for working with MongoDB, including the spring-boot-starter-data-mongodb ‘Starter’.

30.2.1 Connecting to a MongoDB database

You can inject an auto-configured org.springframework.data.mongodb.MongoDbFactory to access Mongo databases. By default the instance will attempt to connect to a MongoDB server using the URL mongodb://localhost/test:

import org.springframework.data.mongodb.MongoDbFactory;
import com.mongodb.DB;

_@Component_
public class MyBean {

    private final MongoDbFactory mongo;

    _@Autowired_
    public MyBean(MongoDbFactory mongo) {
        this.mongo = mongo;
    }

    // ...

    public void example() {
        DB db = mongo.getDb();
        // ...
    }

}

You can set spring.data.mongodb.uri property to change the URL and configure additional settings such as the replica set:

spring.data.mongodb.uri=mongodb://user:[email protected]:12345,mongo2.example.com:23456/test

Alternatively, as long as you’re using Mongo 2.x, specify a host/port. For example, you might declare the following in your application.properties:

spring.data.mongodb.host=mongoserver
spring.data.mongodb.port=27017

	Note
spring.data.mongodb.host and spring.data.mongodb.port are not supported if you’re using the Mongo 3.0 Java driver. In such cases, spring.data.mongodb.uri should be used to provide all of the configuration.

	Tip
If spring.data.mongodb.port is not specified the default of 27017 is used. You could simply delete this line from the sample above.

	Tip
If you aren’t using Spring Data Mongo you can inject com.mongodb.Mongo beans instead of using MongoDbFactory.

You can also declare your own MongoDbFactory or Mongo bean if you want to take complete control of establishing the MongoDB connection.

30.2.2 MongoTemplate

Spring Data Mongo provides a MongoTemplate class that is very similar in its design to Spring’s JdbcTemplate. As with JdbcTemplate Spring Boot auto-configures a bean for you to simply inject:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.stereotype.Component;

_@Component_
public class MyBean {

    private final MongoTemplate mongoTemplate;

    _@Autowired_
    public MyBean(MongoTemplate mongoTemplate) {
        this.mongoTemplate = mongoTemplate;
    }

    // ...

}

See the MongoOperations Javadoc for complete details.

30.2.3 Spring Data MongoDB repositories

Spring Data includes repository support for MongoDB. As with the JPA repositories discussed earlier, the basic principle is that queries are constructed for you automatically based on method names.

In fact, both Spring Data JPA and Spring Data MongoDB share the same common infrastructure; so you could take the JPA example from earlier and, assuming that City is now a Mongo data class rather than a JPA @Entity, it will work in the same way.

package com.example.myapp.domain;

import org.springframework.data.domain.*;
import org.springframework.data.repository.*;

public interface CityRepository extends Repository<City, Long> {

    Page<City> findAll(Pageable pageable);

    City findByNameAndCountryAllIgnoringCase(String name, String country);

}

	Tip
For complete details of Spring Data MongoDB, including its rich object mapping technologies, refer to their reference documentation.

30.2.4 Embedded Mongo

Spring Boot offers auto-configuration for Embedded Mongo. To use it in your Spring Boot application add a dependency on de.flapdoodle.embed:de.flapdoodle.embed.mongo.

The port that Mongo will listen on can be configured using the spring.data.mongodb.port property. To use a randomly allocated free port use a value of zero. The MongoClient created by MongoAutoConfiguration will be automatically configured to use the randomly allocated port.

If you have SLF4J on the classpath, output produced by Mongo will be automatically routed to a logger named org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongo.

You can declare your own IMongodConfig and IRuntimeConfig beans to take control of the Mongo instance’s configuration and logging routing.