How to Connect MongoDB with Spring Boot?

Connecting MongoDB with Spring Boot is straightforward using Spring Data MongoDB. Here's a step-by-step guide:

1. Add Dependencies:

Firstly, add the necessary dependencies to your pom.xml:

<!-- Spring Boot Data MongoDB Starter -->
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-mongodb</artifactId>
</dependency>

If you're using Gradle, you would add this to your build.gradle:

implementation 'org.springframework.boot:spring-boot-starter-data-mongodb'

2. Configure MongoDB Connection:

Update your application.properties or application.yml to set the connection details for MongoDB.

Using application.properties:

# URI for MongoDB (this is for a local MongoDB instance without authentication)
spring.data.mongodb.uri=mongodb://localhost:27017/mydatabase

Using application.yml:

spring:
  data:
    mongodb:
      uri: mongodb://localhost:27017/mydatabase

Note: If your MongoDB setup has authentication or is hosted elsewhere, adjust the URI accordingly.

3. Create Domain Classes:

Define your domain objects as usual, but annotate them with annotations from the org.springframework.data.annotation package:

import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;

@Document
public class User {
    @Id
    private String id;
    private String name;
    private String email;

    // Constructors, getters, setters, etc.
}

4. Create Repository Interfaces:

Spring Data MongoDB allows you to use repository interfaces. For example:

import org.springframework.data.mongodb.repository.MongoRepository;

public interface UserRepository extends MongoRepository<User, String> {
    User findByName(String name);
}

5. Use the Repository:

Now, you can autowire and use this repository in your service classes:

@Service
public class UserService {

    @Autowired
    private UserRepository userRepository;

    public User findByName(String name) {
        return userRepository.findByName(name);
    }

    // Other service methods
}

6. Run Your Application:

Now you can run your Spring Boot application, and it should be able to connect to MongoDB and perform CRUD operations as defined in your repository and service.

Bonus: Using MongoDB Reactive:

If you wish to use the reactive programming model with MongoDB, you would use the spring-boot-starter-data-mongodb-reactive dependency instead, and then your repositories would extend ReactiveMongoRepository.

That's the basic process to integrate MongoDB with Spring Boot. Depending on your exact needs, there may be additional configurations or customizations required.

Setting up Spring Boot for MongoDB integration:

Description: Set up a Spring Boot project for MongoDB integration, preparing the groundwork for MongoDB database connectivity.

Code:

@SpringBootApplication
public class SpringBootMongoDBApplication {
    public static void main(String[] args) {
        SpringApplication.run(SpringBootMongoDBApplication.class, args);
    }
}

MongoDB configuration in Spring Boot example:
- Description: Configure MongoDB in a Spring Boot application, specifying the database connection details.
- Code:
```
# application.properties
spring.data.mongodb.host=localhost
spring.data.mongodb.port=27017
spring.data.mongodb.database=mydb
```
Creating a MongoDB repository in Spring Boot:
- Description: Create a MongoDB repository interface in Spring Boot for performing CRUD operations on MongoDB entities.
- Code:
```
public interface UserRepository extends MongoRepository<User, String> {
    // Custom queries if needed
}
```
Using Spring Data MongoDB with Spring Boot:
- Description: Utilize Spring Data MongoDB in a Spring Boot application to simplify MongoDB data access.
- Code:
```
@Service
public class UserService {

    @Autowired
    private UserRepository userRepository;

    // CRUD operations using userRepository
}
```

Connecting to MongoDB database in Spring Boot application:

Description: Establish a connection to a MongoDB database within a Spring Boot application.

Code:

@Configuration
public class MongoDBConfig extends AbstractMongoClientConfiguration {

    @Override
    protected String getDatabaseName() {
        return "mydb";
    }

    @Override
    public MongoClient mongoClient() {
        return MongoClients.create();
    }
}

Configuring MongoDB properties in Spring Boot:
- Description: Configure MongoDB properties in a Spring Boot application for specifying connection details and other settings.
- Code:
```
# application.properties
spring.data.mongodb.uri=mongodb://localhost:27017/mydb
```

Handling CRUD operations with MongoDB in Spring Boot:

Description: Implement CRUD operations using Spring Boot and MongoDB, leveraging Spring Data MongoDB repositories.

Code:

@Service
public class UserService {

    @Autowired
    private UserRepository userRepository;

    public User saveUser(User user) {
        return userRepository.save(user);
    }

    // Other CRUD operations
}

MongoDB template usage in Spring Boot applications:

Description: Utilize the MongoDB template for more flexible and customizable interactions with MongoDB in Spring Boot.

Code:

@Service
public class UserService {

    @Autowired
    private MongoTemplate mongoTemplate;

    public List<User> findUsersByAgeRange(int minAge, int maxAge) {
        Query query = new Query(Criteria.where("age").gte(minAge).lte(maxAge));
        return mongoTemplate.find(query, User.class);
    }

    // Other MongoDB template operations
}

Indexing and querying in Spring Boot with MongoDB:
- Description: Implement indexing and querying strategies for MongoDB in a Spring Boot application to enhance performance.
- Code:
```
@Document
public class User {

    @Indexed(unique = true)
    private String username;
    // Other fields and methods
}
```
Connecting Spring Boot to MongoDB Atlas:
- Description: Configure Spring Boot to connect to MongoDB Atlas, a cloud-based MongoDB service.
- Code:
```
# application.properties
spring.data.mongodb.uri=mongodb+srv://<username>:<password>@cluster0.mongodb.net/mydb
```

Handling transactions with MongoDB in Spring Boot:

Description: Implement transactional operations with MongoDB in a Spring Boot application, ensuring data consistency.

Code:

@Service
@Transactional
public class TransactionalService {

    @Autowired
    private UserRepository userRepository;

    public void performTransactionalOperation(User user1, User user2) {
        userRepository.save(user1);
        userRepository.save(user2);
        // Additional operations
    }
}

Securing MongoDB connections in Spring Boot:
- Description: Secure MongoDB connections in a Spring Boot application by using authentication and encryption.
- Code:
```
# application.properties
spring.data.mongodb.uri=mongodb://username:password@localhost:27017/mydb
```
Handling nested documents in Spring Boot with MongoDB:
- Description: Manage nested documents in MongoDB entities within a Spring Boot application.
- Code:
```
@Document
public class Order {

    private String orderId;
    private List<Item> items;
    // Other fields and methods
}
```
Integration testing with MongoDB in Spring Boot:
- Description: Conduct integration testing for MongoDB operations in a Spring Boot application using tools like @DataMongoTest.
- Code:
```
@RunWith(SpringRunner.class)
@DataMongoTest
public class UserRepositoryIntegrationTest {

    @Autowired
    private UserRepository userRepository;

    // Test methods
}
```