Introduction to Spring Data MongoDB

Spring Data MongoDB is a powerful framework that simplifies data access and manipulation in Spring-based applications using MongoDB. This guide covers key concepts and steps for getting started with Spring Data MongoDB, including adding dependencies, defining documents, creating repositories, and using CRUD operations.

Key Concepts of Spring Data MongoDB

• Spring Data MongoDB: A framework that provides easy integration with MongoDB, reducing boilerplate code and simplifying data access.
• Documents: Classes that represent MongoDB collections.
• Repositories: Interfaces that provide CRUD operations and custom query methods.
• CRUD Operations: Create, Read, Update, and Delete operations.

Adding Dependencies

Include the Spring Data MongoDB dependency in your pom.xml file:

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

Defining Documents

Create a document class that maps to a MongoDB collection:

Example: User.java

// User.java
package com.example.myapp.model;

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

@Document(collection = "users")
public class User {

    @Id
    private String id;
    private String username;
    private String password;

    // Getters and setters
}

Creating Repositories

Create a repository interface for the document, extending MongoRepository:

Example: UserRepository.java

// UserRepository.java
package com.example.myapp.repository;

import com.example.myapp.model.User;
import org.springframework.data.mongodb.repository.MongoRepository;
import org.springframework.stereotype.Repository;

@Repository
public interface UserRepository extends MongoRepository {
}

Using CRUD Operations

Use the repository to perform CRUD operations on the document:

Example: UserService.java

// UserService.java
package com.example.myapp.service;

import com.example.myapp.model.User;
import com.example.myapp.repository.UserRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class UserService {

    @Autowired
    private UserRepository userRepository;

    public List findAllUsers() {
        return userRepository.findAll();
    }

    public User findUserById(String id) {
        return userRepository.findById(id).orElse(null);
    }

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

    public void deleteUser(String id) {
        userRepository.deleteById(id);
    }
}

Testing Spring Data MongoDB

Test your Spring Data MongoDB setup to ensure it works as expected:

Example: UserServiceTests.java

// UserServiceTests.java
package com.example.myapp;

import com.example.myapp.model.User;
import com.example.myapp.repository.UserRepository;
import com.example.myapp.service.UserService;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.mock.mockito.MockBean;

import java.util.Optional;

import static org.assertj.core.api.Assertions.assertThat;
import static org.mockito.Mockito.when;

@SpringBootTest
public class UserServiceTests {

    @Autowired
    private UserService userService;

    @MockBean
    private UserRepository userRepository;

    @Test
    public void testFindUserById() {
        User user = new User();
        user.setId("1");
        user.setUsername("testuser");
        user.setPassword("password");

        when(userRepository.findById("1")).thenReturn(Optional.of(user));

        User foundUser = userService.findUserById("1");

        assertThat(foundUser.getUsername()).isEqualTo("testuser");
    }
}

Key Points

Conclusion

Spring Data MongoDB simplifies data access and manipulation in Spring-based applications by providing easy integration with MongoDB. By understanding and implementing documents, repositories, and CRUD operations, you can effectively manage data in your Spring Boot application. Happy coding!