Recently, we’ve seen a rise in popularity of NoSQL databases. MongoDB has rapidly gained popularity in the enterprise and the Spring community.

While developing and testing Spring Boot applications with MongoDB as the data store, it is common to use the lightweight Embedded MongoDB rather than running a full-fledged server. As the embedded MongoDB runs in memory, it is blazing fast and will save you lot of time during both development and when running your tests whether it's in your development machine or a CI server.

I have covered setting up MongoDB in a Spring Boot application here.

In this post, I’ll discuss how to use embedded MongoDB in a Spring Boot application.

I posted a video here that explains the Spring Boot application that I’ll use in this post.

The Maven POM

Embedded MongoDB downloads and fires up a real MongoDB instance. You get the benefit of talking to an instance loaded in memory with the same capabilities as your production environment. The Maven POM dependency to include Embedded MongoDB is this:

<dependency>
    <groupId>de.flapdoodle.embed</groupId>
    <artifactId>de.flapdoodle.embed.mongo</artifactId>
    <version>1.50.5</version>
</dependency>

You also need to include the embedmongo-spring dependency that provides Spring Factory Bean for Embedded MongoDB, like this:

<dependency>
    <groupId>cz.jirutka.spring</groupId>
    <artifactId>embedmongo-spring</artifactId>
    <version>RELEASE</version>
</dependency>

Finally, with this spring-boot-starter-data-mongodb dependency pulled in, you should be all set to use embedded MongoDB in your Spring Boot app.

<dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-data-mongodb</artifactId>
</dependency>

The complete pom.xml is this:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>guru.springframework</groupId>
    <artifactId>spring-boot-mongodb</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>spring-boot-mongodb</name>
    <description>Demo project for Spring Boot and Mongo DB</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.1.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>de.flapdoodle.embed</groupId>
            <artifactId>de.flapdoodle.embed.mongo</artifactId>
            <version>1.50.5</version>
        </dependency>
        <dependency>
            <groupId>cz.jirutka.spring</groupId>
            <artifactId>embedmongo-spring</artifactId>
            <version>RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-mongodb</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>


</project>

The MongoDB Config

You need to provide a MongoTemplate bean to Spring Boot for your application to interact with the embedded MongoDB instance. You typically use a @Configuration class, like this:

package guru.springframework.config;

import java.io.IOException;
import cz.jirutka.spring.embedmongo.EmbeddedMongoFactoryBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.mongodb.core.*;
import com.mongodb.MongoClient;


@Configuration
public class MongoConfig {

    private static final String MONGO_DB_URL = "localhost";
    private static final String MONGO_DB_NAME = "embeded_db";
    @Bean
    public MongoTemplate mongoTemplate() throws IOException {
        EmbeddedMongoFactoryBean mongo = new EmbeddedMongoFactoryBean();
        mongo.setBindIp(MONGO_DB_URL);
        MongoClient mongoClient = mongo.getObject();
        MongoTemplate mongoTemplate = new MongoTemplate(mongoClient, MONGO_DB_NAME);
        return mongoTemplate;
    }
}

In this MongoConfig class, EmbeddedMongoFactoryBean is a FactoryBean for embedded MongoDB that runs MongoDB as a managed process and exposes a pre-configured instance of MongoClient.

This is all you need to do to start using Embedded MongoDB in a Spring Boot application.

Note: By default, your application will connect to the test database. For a different database, set the spring.data.mongodb.database property in your application.properties configuration file.

You can download the source code from git here.