Spring Boot - MongoRepository with Example

Spring Boot - MongoRepository with Example

The MongoRepository interface in Spring Boot is a part of Spring Data MongoDB. It provides a way to perform CRUD operations and queries on MongoDB documents using Spring's familiar repository abstraction. Below is an example of how to use MongoRepository with Spring Boot:

1. Dependencies:

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

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

2. Application Properties:

Configure MongoDB in the application.properties or application.yml:

spring.data.mongodb.uri=mongodb://localhost:27017/mydb

Replace mydb with your database name.

3. Create a Document:

For MongoDB with Spring, we use the @Document annotation for entities:

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; // ... getters, setters, constructors, etc. }

Here, @Id indicates the id property of the MongoDB document.

4. Create Repository:

Now, create a repository interface for the User document:

import org.springframework.data.mongodb.repository.MongoRepository; public interface UserRepository extends MongoRepository<User, String> { User findByName(String name); }

By extending MongoRepository, you get basic CRUD operations for free. Additionally, Spring Data allows you to define query methods in the repository, like findByName.

5. Use the Repository:

With the repository in place, you can now use it in a service or controller:

import org.springframework.beans.factory.annotation.Autowired; import org.springframework.stereotype.Service; @Service public class UserService { private final UserRepository userRepository; @Autowired public UserService(UserRepository userRepository) { this.userRepository = userRepository; } public User saveUser(User user) { return userRepository.save(user); } public User getUserByName(String name) { return userRepository.findByName(name); } // ... other methods }

6. Run Your Application:

Now, if you run your Spring Boot application and have a MongoDB instance running at the specified location (in our case, localhost:27017), you can use the UserService to interact with the MongoDB instance and perform CRUD operations on the User documents.

Conclusion:

This was a basic introduction to MongoRepository in Spring Boot. The power of Spring Data MongoDB lies in its ability to generate queries from method names, provide custom query methods using the @Query annotation, support for paging and sorting, and many other advanced features.

Examples

  1. Introduction to MongoRepository in Spring Boot:

    • Description: MongoRepository is part of Spring Data MongoDB and provides a set of abstractions and methods for interacting with MongoDB data stores.
    • Code:
      // Example MongoRepository interface public interface UserRepository extends MongoRepository<User, String> { }

  2. CRUD operations with MongoRepository in Spring Boot:

    • Description: MongoRepository supports standard CRUD operations like save, findById, findAll, delete, etc., out of the box.
    • Code:
      // Example CRUD operations with MongoRepository userRepository.save(new User("John Doe", 25)); Optional<User> user = userRepository.findById("userId"); List<User> allUsers = userRepository.findAll(); userRepository.delete(user.get());

  3. Custom queries with MongoRepository in Spring Boot:

    • Description: MongoRepository allows the creation of custom queries using method names or @Query annotations.
    • Code:
      // Custom query with method name List<User> findByAgeGreaterThan(int age); // Custom query with @Query annotation @Query("{ 'name' : ?0, 'age' : { $gte: ?1 } }") List<User> findUsersWithNameAndAge(String name, int age);

  4. Pagination and sorting with MongoRepository in Spring Boot:

    • Description: MongoRepository supports pagination and sorting for handling large datasets.
    • Code:
      // Pagination and sorting with MongoRepository Page<User> usersPage = userRepository.findAll(PageRequest.of(0, 10, Sort.by("name")));

  5. Handling embedded documents with MongoRepository in Spring Boot:

    • Description: MongoRepository seamlessly handles embedded documents and relationships between entities.
    • Code:
      // Example entity with embedded document public class User { private String name; private Address address; // getters and setters }

  6. Indexing and optimization with MongoRepository in Spring Boot:

    • Description: MongoRepository can leverage MongoDB indexing for optimizing query performance.
    • Code:
      // Indexing with MongoRepository @Document @CompoundIndex(def = "{'name': 1, 'age': -1}") public class User { // entity fields }

  7. Using QueryDSL with MongoRepository in Spring Boot:

    • Description: QueryDSL can be integrated with MongoRepository for more complex queries and dynamic query building.
    • Code:
      // QueryDSL with MongoRepository public interface UserRepository extends QuerydslMongoPredicateExecutor<User>, MongoRepository<User, String> { // custom queries with QueryDSL }

  8. Transaction management with MongoRepository in Spring Boot:

    • Description: MongoRepository supports transactions, allowing multiple operations to be executed within a single transaction.
    • Code:
      // Transactional method with MongoRepository @Transactional public void performTransactionalOperation() { userRepository.save(new User("Alice", 30)); userRepository.save(new User("Bob", 35)); }

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