In this tutorial, we will discuss how to connect two different MongoDB databases from your Spring boot application. This article assumes you already have MongoDB integrated into your project, hence this post skips the basics.
To connect to multiple MongoDB databases, we need to use MongoClientFactoryBean to create multiple MongoClient instances that connects to two different databases.
First let us add two set of MongoDB connection properties to your application.properties file corresponding to each DB.
# Primary MongoDB configs spring.data.mongodb.primary.host=localhost spring.data.mongodb.primary.port=27017 spring.data.mongodb.primary.username=root spring.data.mongodb.primary.password=admin spring.data.mongodb.primary.database=movies_db spring.data.mongodb.primary.authentication-database=admin # Secondary MongoDB configs spring.data.mongodb.secondary.host=localhost spring.data.mongodb.secondary.port=27018 spring.data.mongodb.secondary.username=root spring.data.mongodb.secondary.password=admin spring.data.mongodb.secondary.database=movies_db2 spring.data.mongodb.secondary.authentication-database=admin
MongoDB Config
Next, we will bind these configuration properties property to the MongoProperties object using the @ConfigurationProperties annotation.
And then, we will use these properties to create a MongoClient bean. The MongoClient is the entry point to the MongoDB driver API.
We then have to register a MongoClient via MongoDatabaseFactory. The MongoDatabaseFactory is used to bootstrap the connectivity to the database. Finally we can use the MongoDatabaseFactory instance to configure the MongoTemplate .
The MongoTemplate will be used for performing all Mongo DB CRUD operations including BSON queries or updates.
Primary MongoDB Config:
@Configuration
@EnableMongoRepositories(basePackages = "com.stacktips.app.repository.primary",
mongoTemplateRef = "primaryMongoTemplate")
public class PrimaryMongoConfig {
@Primary
@Bean("primaryMongoProperties")
@ConfigurationProperties(prefix = "spring.data.mongodb.primary")
public MongoProperties primaryMongoProperties() {
return new MongoProperties();
}
@Primary
@Bean(name = "primaryMongoClient")
public MongoClient primaryMongoClient(@Qualifier("primaryMongoProperties") MongoProperties mongoProperties) {
ServerAddress serverAddress = new ServerAddress(mongoProperties.getHost(), mongoProperties.getPort());
MongoClientSettings settings = MongoClientSettings.builder()
.applyToClusterSettings(builder ->
builder.hosts(List.of(serverAddress)))
.credential(MongoCredential.createCredential(
mongoProperties.getUsername(),
mongoProperties.getAuthenticationDatabase(),
mongoProperties.getPassword()))
.build();
return MongoClients.create(settings);
}
@Primary
@Bean(name = "primaryMongoFactory")
public MongoDatabaseFactory mongoDatabaseFactory(
@Qualifier("primaryMongoClient") MongoClient mongoClient,
@Qualifier("primaryMongoProperties") MongoProperties mongoProperties) {
return new SimpleMongoClientDatabaseFactory(mongoClient, mongoProperties.getDatabase());
}
@Primary
@Bean(name = "primaryMongoTemplate")
public MongoTemplate mongoTemplate(
@Qualifier("primaryMongoFactory") MongoDatabaseFactory mongoDatabaseFactory) {
return new MongoTemplate(mongoDatabaseFactory);
}
}
Important Notes:
- The
@EnableMongoRepositoriesis the key here. This will scan all mongo repository from specific package as defined. All repositories that will be used to - The
mongoTemplateRefis used to configure the name of theMongoTemplatebean to be used with the repositories detected. - The
@Primaryannotation indicates that the a bean should be given preference when multiple candidates are qualified to autowire a single-valued dependency. If exactly one 'primary' bean exists among the candidates, it will be the autowired value.
Secondary MongoDB Config:
The secondary mongo db config is similar to the primary, except for the @Primary annotation and it will read properties with spring.data.mongodb.secondary prefix.
@Configuration
@EnableMongoRepositories(basePackages = "com.stacktips.app.repository.secondary",
mongoTemplateRef = "secondaryMongoTemplate")
public class SecondaryMongoConfig {
@Bean("secondaryMongoProperties")
@ConfigurationProperties(prefix = "spring.data.mongodb.secondary")
public MongoProperties secondaryMongoProperties() {
return new MongoProperties();
}
@Bean(name = "secondaryMongoClient")
public MongoClient secondaryMongoClient(
@Qualifier("secondaryMongoProperties") MongoProperties mongoProperties) {
ServerAddress serverAddress = new ServerAddress(mongoProperties.getHost(), mongoProperties.getPort());
MongoClientSettings settings = MongoClientSettings.builder()
.applyToClusterSettings(builder -> builder.hosts(List.of(serverAddress)))
.credential(MongoCredential.createCredential(
mongoProperties.getUsername(),
mongoProperties.getAuthenticationDatabase(),
mongoProperties.getPassword()))
.build();
return MongoClients.create(settings);
}
@Bean(name = "secondaryMongoFactory")
public MongoDatabaseFactory mongoDatabaseFactory(
@Qualifier("secondaryMongoClient") MongoClient mongoClient,
@Qualifier("secondaryMongoProperties") MongoProperties mongoProperties) {
return new SimpleMongoClientDatabaseFactory(mongoClient, mongoProperties.getDatabase());
}
@Bean(name = "secondaryMongoTemplate")
public MongoTemplate mongoTemplate(
@Qualifier("secondaryMongoFactory") MongoDatabaseFactory mongoDatabaseFactory) {
return new MongoTemplate(mongoDatabaseFactory);
}
}
In the above example, we're defining two MongoTemplate beans, one for each database. We're passing in the MongoClient instances created by the MongoClientFactoryBean beans, along with the corresponding database name from the MongoProperties beans.
Mongo Repositories
In this example, we will created a two repositories to perform CRUD operation. Note that they reside in two different packages, i.e. com.stacktips.app.repository.primary and com.stacktips.app.repository.secondary.
Here we are using extending MongoRepository to perform the CRUD operations, but the same will work for custom repository that uses MongoTemplate.
package com.stacktips.app.repository.primary;
import com.stacktips.app.model.Movie;
import org.springframework.data.mongodb.repository.MongoRepository;
import org.springframework.stereotype.Repository;
@Repository
public interface PrimaryMovieRepository extends MongoRepository<Movie, String> {
}
Secondary Mongo Repository:
package com.stacktips.app.repository.secondary;
import com.stacktips.app.model.Movie;
import org.springframework.data.mongodb.repository.MongoRepository;
import org.springframework.stereotype.Repository;
@Repository
public interface SecondaryMovieRepository extends MongoRepository<Movie, String> {
}
No that we have everything, let us now inject these repositories into our service:
@Service
public class MovieService {
private final PrimaryMovieRepository primaryMovieRepository;
private final SecondaryMovieRepository secondaryMovieRepository;
public MovieService(
PrimaryMovieRepository primaryMovieRepository,
SecondaryMovieRepository secondaryMovieRepository) {
this.primaryMovieRepository = primaryMovieRepository;
this.secondaryMovieRepository = secondaryMovieRepository;
}
public Movie savePrimary(Movie movie) {
return primaryMovieRepository.save(movie);
}
public List<Movie> findAllPrimary() {
return primaryMovieRepository.findAll();
}
public Movie saveSecondary(Movie movie) {
return secondaryMovieRepository.save(movie);
}
public List<Movie> findAllSecondary() {
return secondaryMovieRepository.findAll();
}
}
That's it! With the above configuration, you should be able to connect to multiple MongoDB Databases from your Spring Boot application.
For complete project source code checkout of the download link.