DEV Community: Onatade Abdulmajeed

Top 5 Spring Dependency Injection Best Practices You Need

Onatade Abdulmajeed — Sun, 05 Apr 2026 16:27:37 +0000

Introduction
Understanding Dependency Injection
Best Practices for Effective Dependency Injection
Final Thoughts
Additional Resources

Dependency Injection is the core of the Spring Framework.

Introduction

In the early days of Java, there were lots of heavier enterprise Java technologies for enterprise applications that provided enterprise solutions to programmers. However, it was not easy to maintain the applications because it was tightly coupled with the framework.

The Spring Framework provided a very simple, leaner, and lighter programming model compared with other existing Java technologies and it is one of the most widely used frameworks for building robust and scalable Java applications.

Spring makes dependency injection possible by using features such as Inversion of Control (IoC), and aspect-oriented programming (AOP). Spring allows developers to build applications with simple, framework-independent classes that are easy to test and maintain by using many available design patterns, but it focused on the Plain Old Java Object (POJO) programming model.

At the core of Spring lies Dependency Injection (DI), a design pattern where a class receives its dependencies from an external source rather than creating them internally, making applications easier to manage, test, and extend.

In this article, we’ll explore the top 5 Dependency Injection best practices in Spring that will help you build cleaner, more maintainable, and scalable applications.

Understanding Dependency Injection

Dependency injection (DI) is a software design pattern whereby objects define their dependencies (that is, the other objects with which they work) only through constructor arguments, arguments to a factory method, or properties that are set on the object instance after it is constructed or returned from a factory method.

In the Spring Framework, the container creates objects (beans) and injects their dependencies at runtime. This is known as Inversion of Control (IoC), where control over object creation is handled by Spring instead of the application code, resulting in cleaner, more loosely coupled systems.

Core Benefits of Using Dependency Injection (DI) in Spring

Loose Coupling: Components have minimal dependencies on each other and interact through well-defined interfaces rather than concrete implementations.
Easier Testing: Dependencies can be easily replaced with mocks or stubs, making unit testing simpler and more effective.
Flexibility: You can switch between different implementations without modifying the dependent class.
Maintainability: Since dependencies are managed externally, the code is easier to extend, update, and refactor.
Scalability: Applications can grow and evolve without getting tangled in complex object creation logic.

Common Ways to Use Dependency Injection (DI) in Spring

Spring supports three main ways to inject dependencies:

1. Constructor Injection (Recommended): Dependencies are passed through a class constructor. It allows for immutable objects and ensures the bean is never returned in an uninitialized state.

@Component
public class UserService {

    private final UserRepository userRepository;

    // Constructor Injection
    public UserService(UserRepository userRepository) {
        this.userRepository = userRepository;
    }

    public void getUser() {
        userRepository.findUser();
    }
}

2. Setter Injection (Optional): Dependencies are provided through setter methods after the bean has been instantiated.

@Component
public class UserService {

    private UserRepository userRepository;

    // Setter Injection
    @Autowired
    public void setUserRepository(UserRepository userRepository) {
        this.userRepository = userRepository;
    }

    public void getUser() {
        userRepository.findUser();
    }
}

3. Field Injection (Not recommended): Dependencies are injected directly into class fields. It makes testing hard and reduces clarity.

@Component
public class UserService {

    @Autowired
    private UserRepository userRepository;
}

Best Practices for Effective Dependency Injection.

1. Prefer Constructor Injection

Using constructor-based Dependency Injection is widely regarded as the best practice in Spring Framework. By requiring dependencies to be passed through a class’s constructor, you ensure that a class’s dependencies are provided at the time of object creation.

Advantages of Constructor Injection

Immutability: Dependencies can be marked as final, ensuring they are set only once during creation and cannot be changed later, which increases safety.
Guaranteed Initialization: An object cannot be instantiated without its required dependencies, preventing null pointer exceptions and ensuring the object is always in a valid state.
Easier Unit Testing: Dependencies can be easily mocked and passed into the constructor during testing without requiring reflection or specialized frameworks.

@Service
public class OrderService {
    private final OrderRepository orderRepository;
    private final PaymentProcessor paymentProcessor;

    @Autowired
    public OrderService(OrderRepository orderRepository, PaymentProcessor paymentProcessor) {
        this.orderRepository = orderRepository;
        this.paymentProcessor = paymentProcessor;
    }

    public void placeOrder(Order order) {
        paymentProcessor.process(order);
        orderRepository.save(order);
    }
}

2. Use @Autowired Wisely

The @Autowired annotation injects an instance of a class automatically. While it simplifies wiring, if used carelessly it can lead to hidden dependencies, reduced clarity, and difficulties in testing.

Best Practices for @Autowired

Prefer Constructor Injection: Use @Autowired on constructors rather than fields. This enforces immutability and makes dependencies explicit.
Avoid Field Injection: Direct field injection hides dependencies and is generally discouraged for production-grade code.
Avoid Autowiring Static Fields: Spring's Dependency Injection is designed for instance-level beans.

@Service
public class PaymentService {
    private final PaymentGateway paymentGateway;

    @Autowired
    public PaymentService(PaymentGateway paymentGateway) {
        this.paymentGateway = paymentGateway;
    }

    public void processPayment(Order order) {
        paymentGateway.charge(order);
    }
}

3. Leverage Qualifiers

Why Qualifiers Are Needed?

In many Spring applications, you may have multiple beans of the same type. For example, two different implementations of a PaymentGateway interface. When Spring attempts to inject a dependency, it can’t automatically decide which bean to use, leading to ambiguity. The @Qualifier annotation resolves this by explicitly specifying which bean should be injected.

This is where the @Qualifier annotation becomes useful. It allows you to specify exactly which bean should be injected, giving you more control over dependency resolution.

@Component("emailService")
public class EmailService implements NotificationService {}

@Component("smsService")
public class SmsService implements NotificationService {}

@Component
public class UserService {

    private final NotificationService notificationService;

    public UserService(@Qualifier("emailService") NotificationService notificationService) {
        this.notificationService = notificationService;
    }
}

4. Scope Management

Managing Spring bean scopes carefully is crucial for application performance, memory efficiency, and ensuring thread safety. A bean's scope defines its lifecycle and visibility within the Spring container. Choosing the wrong scope can lead to memory leaks, inconsistent data, and concurrency issues. The most commonly used scopes are:

Singleton (Default): A single instance per Spring container (ApplicationContext). Ideal for stateless services, repositories, and controllers.

@Component
public class OrderRepository {
    // Singleton by default
}

Prototype: A new instance is created every time the bean is requested. Ideal for stateful beans.

@Component
@Scope("prototype")
public class ShoppingCart {
    private List<Item> items = new ArrayList<>();
}

Request: A single instance per HTTP request (web-aware only). Created per request, destroyed after the request is completed.

@Component
@Scope("request")
public class RequestLogger {
    private final String requestId = UUID.randomUUID().toString();
}

Session: One instance per HTTP session (web-aware only).

@Component
@Scope("session")
public class UserPreferences {
    private String theme;
    private String language;
}

Best Practices for Scope Management

Default to Singleton: For stateless beans (e.g., service classes), use the default singleton scope to save memory.
Use Prototype for Stateful Beans: Use prototype if the bean needs to maintain internal state that is specific to the caller.
Be Careful with Mutable State: If a singleton bean has mutable member variables, it must be thread-safe.
Avoid Overusing Prototype: It can lead to memory overhead and and performance issues if not managed carefully.

5. Avoid Over-Complexity

Avoiding over-complexity in Spring Dependency Injection comes down to keeping things simple and not over-engineering your application. It’s best to stick with constructor injection, use annotation-based configuration instead of XML, and design your application in a way that avoids circular dependencies. Following these practices helps keep your code clean, readable, and easy to maintain.

Tips for avoiding excessive use of Dependency Injection (DI):

Keep Constructor Simple
Prefer annotations and configuration classes over XML
Use Proper Lifecycle Management
Refactor large constructors
Inject what is necessary

Example of a complex Dependency Injection (DI) configuration:

@Component
public class OrderService {

    @Autowired
    private PaymentService paymentService;

    @Autowired
    private EmailService emailService;

    @Autowired
    private SmsService smsService;

    @Autowired
    private AuditService auditService;
}

Example of a simplified Dependency Injection (DI) configuration:

@Component
public class OrderService {

    private final PaymentService paymentService;

    public OrderService(PaymentService paymentService) {
        this.paymentService = paymentService;
    }
}

Final Thoughts

Dependency Injection is a core part of the Spring Framework, making it easier to build applications that are clean, modular, and easy to maintain. In this article, we covered five practical best practices—from using constructor injection and handling @Autowired carefully, to working with qualifiers, managing bean scopes, and keeping your configuration simple.

Each of these practices helps improve how your code is structured. Constructor injection makes dependencies clear and required, qualifiers remove ambiguity, proper scope management improves efficiency, and avoiding unnecessary complexity keeps your application easier to understand.

When you apply these principles, your code becomes easier to test, extend, and scale over time. Spring gives you powerful tools, but using them well is what truly makes the difference.

If you’ve worked with Spring Dependency Injection before, feel free to share your experience or any tips you’ve learned along the way.

Additional Resources

Here are some useful resources that will help to deepen your understanding of Dependency Injection in Spring:

Official Spring Documentation

https://docs.spring.io/spring-framework/reference/core/beans/dependencies/factory-collaborators.html

Spring Guides & Tutorials

Books Worth Checking Out

Spring in Action by Craig Walls
Pro Spring by Clarence Ho and Rob Harrop

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Building an AI Blog Generator with Node.js, OpenAI & Notion MCP

Onatade Abdulmajeed — Sat, 28 Mar 2026 18:41:00 +0000

This is a submission for the Notion MCP Challenge

What I Built

I built an AI-powered Blog Generator that takes a user’s topic, generates a structured blog outline using OpenAI, and automatically stores the result inside a Notion database.

The system works as a CLI tool built with Node.js and integrates both OpenAI API and Notion API to automate content creation workflows.

This project demonstrates how AI can be combined with productivity tools to remove manual writing effort and streamline content generation.

Video Demo

Watch the full demo here:

https://youtu.be/0e8DcL7EjuY

GitHub Repository

https://github.com/Spider1201/AI-Blog

How I Used Notion MCP

I used Notion as the final output layer of my AI system.

Here’s how it works:

After generating a blog outline using OpenAI, the content is processed in Node.js
A new page is created inside a structured database
Properties like title and status are automatically filled

This effectively turns Notion into an AI-powered content storage system.

What this unlocks:

Automated documentation
AI-powered content pipelines
Structured knowledge storage
Zero manual copy-paste workflow

Tech Stack

Node.js
OpenAI API (GPT-4o-mini)
Notion MCP
dotenv
prompt-sync

Key Features

AI-generated blog outlines
Automatic Notion page creation
CLI-based interaction
Clean structured output system

What I Learned

This project helped me understand:

How to integrate multiple APIs in a real workflow
Prompt engineering for structured AI outputs
Working with Notion as a backend database
Handling API limitations and data chunking
Building automation tools with Node.js

Conclusion

This project shows how AI can transform simple workflows into automated systems. By combining OpenAI with Notion, I was able to build a tool that turns ideas into structured content instantly.

Excited to keep improving this and building more AI-powered tools

[Boost]

Onatade Abdulmajeed — Tue, 24 Mar 2026 13:31:43 +0000

Onatade Abdulmajeed

Mar 23

MongoDB vs MySQL: Choosing the Right Database for Your Project

#database #mongodb #mysql #backend

Comments 1

7 min read

MongoDB vs MySQL: Choosing the Right Database for Your Project

Onatade Abdulmajeed — Mon, 23 Mar 2026 13:46:27 +0000

Introduction
What is MongoDB?
Advantages of MongoDB
Disadvantages of MongoDB
What is MySQL
Advantages of MySQL
Disadvantages of MySQL
Differences between MongoDB vs MySQL
MongoDB vs MySQL: Which One Should You Use?
Conclusion

Introduction

Choosing a suitable database for your project is an important decision when building modern applications. Databases are responsible for storing, managing, and retrieving data efficiently. The type of database you choose can affect the performance, scalability, and flexibility of your application.

MongoDB and MySQL are two of the most popular database technologies used by developers today. While both are powerful tools for managing data, they serve different purposes in how they store and manage information. In this article, we will explore the differences between MongoDB and MySQL, discuss their advantages, and help you choose the right database for your project.

“Data is a precious thing and will last longer than the systems themselves.”

— Tim Berners-Lee

What is MongoDB?

MongoDB is a NoSQL document-oriented database designed to store and manage large amounts of unstructured or semi-structured data. Unlike traditional relational databases, MongoDB does not store data in tables and rows. Instead, it stores data in flexible JSON-like documents, which are grouped into collections.

MongoDB was developed in 2007 in New York by Kevin P. Ryan, Dwight Merriman, and Eliot Horowitz. The company behind it was originally called 10gen, which built the MongoDB open-source database. The database was first released in 2009 and quickly gained attention for its flexible document-based approach to storing data.

In 2013, the company officially changed its name from 10gen to MongoDB Inc., reflecting the growing popularity of the database. The name MongoDB itself was inspired by the word “humongous,” highlighting its ability to handle large volumes of data.

You can read more about MongoDB's history on the MongoDB official website.

Advantages of MongoDB

Flexible and Dynamic Schema

One of the biggest advantages of MongoDB is its flexible schema. Developers can store data without defining a strict structure beforehand, making it easier to adjust the database as application requirements evolve.
High Performance and Speed

The document-based structure combined with indexing helps deliver fast read and write operations, which is especially useful for applications that handle large amounts of data.
Rich Query Language and Indexing

It provides a powerful query language along with different indexing options that help improve how quickly data can be searched and retrieved.
Multi-Document ACID Transactions

Support for ACID transactions helps ensure that multiple database operations remain consistent and reliable, even when dealing with complex updates.
Handles Unstructured Data Well

This makes it a strong option for applications that deal with unstructured or semi-structured data, such as logs, user activity, or content-driven platforms.
Good for Large-Scale Applications

The database is designed to scale horizontally, allowing data to be distributed across multiple servers as the application grows.

Disadvantages of MongoDB

High Memory Usage

MongoDB uses memory to boost performance, which can result in higher memory usage.
No Schema Enforcement

Flexibility can lead to data inconsistency if not handled carefully.
Limited Support for Joins

MongoDB supports basic joins, but it is less efficient for complex relationships.

What is MySQL?

MySQL is an open-source, relational database management system (RDBMS) that stores data in structured tables consisting of rows and columns. It uses Structured Query Language (SQL) to manage and retrieve data.

MySQL was originally developed in 1995 by Michael Widenius, David Axmark, and Allan Larsson at the Swedish company MySQL AB. Designed for speed, reliability, and ease of integration with web applications, it quickly became one of the most widely adopted open-source databases.
In 2008, Sun Microsystems acquired MySQL AB, integrating the database into its software portfolio. Following Oracle Corporation’s acquisition of Sun Microsystems in 2010, MySQL became part of Oracle’s suite of database technologies, where it continues to be maintained and developed.

You can learn more about MySQL on the MySQL official website.

Advantages of MySQL

High Performance

MySQL is optimized for speed and can handle large amounts of data efficiently. Its indexing and query optimization features help deliver fast read and write operations, making it suitable for many web applications.
Ease of Use and Management

MySQL is relatively easy to install, configure, and manage. Its straightforward structure and large ecosystem of tools make it accessible for both beginners and experienced developers.
Strong Community Support

As one of the most widely used relational databases, MySQL benefits from a large global community, extensive documentation, and a wide range of tools that support development and database management.
Mature and Stable Technology

Having been around for decades, MySQL is well-tested and trusted for building reliable applications.
Easy Integration with Web Applications

It works well with many programming languages and frameworks, including Java, Python, PHP, and Node.js.
Cross-Platform Compatibility

It runs on all major operating systems, including Windows, Linux, macOS, and various Unix versions.

Disadvantages of MySQL

Scalability Issues

Its single-node architecture can create bottlenecks under high load and limit horizontal scaling for write-heavy workloads.
Error messages can be less descriptive

Debugging query errors sometimes requires deeper knowledge
Less Flexible with JSON

MySQL supports JSON, but it is less flexible compared to document-based databases.

Differences between MongoDB vs MySQL

This section highlights some of the key differences between MongoDB and MySQL.

Database Type

MongoDB is a NoSQL database while MySQL is a relational database management system (RDBMS)
Database Structure

MongoDB stores data as JSON documents, whereas MySQL stores data in rows and tables.

Data in MySQL look like the below table:

In MongoDB it will look like this:

   {
      "student_id": "0123",
      "first_name": "John",
      "last_name": "Doe"
   }

Query Language MongoDB uses MongoDB Query Language (MQL) to interact with data stored in documents. MySQL uses Structured Query Language (SQL) to manage and retrieve data from relational tables.

Finding Data in MongoDB:

   db.students.find()

Finding Data in MySQL:

   SELECT * FROM students;

Inserting data in MongoDB

   db.students.insertOne({
      student_id: "0123",
      first_name: "John",
      last_name: "Doe"
   })

Inserting data in MySQL

   INSERT INTO students (student_id, first_name, last_name)
   VALUES ('0123', 'John', 'Doe');

Updating data in MongoDB

   db.students.updateOne(
      { student_id: "0123" },
      { $set: { first_name: "Johnny" } }
   )

Updating data in MySQL

   UPDATE students
   SET first_name = 'Johnny'
   WHERE student_id = '0123';

Deleting data in MongoDB

   db.students.deleteOne({ student_id: "0123" })

Deleting data in MySQL

   DELETE FROM students
   WHERE student_id = '0123';

Data Grouping

In MongoDB, documents that belong to the same type or category are grouped together in a collection.

In MySQL, related data is organized in tables, where each row represents a record.
Scalability

MongoDB provides a way to scale your databases horizontally across hundreds of nodes, allowing data to be distributed across multiple servers.

MySQL scales vertically, this involves adding more resources (CPU, RAM, storage) to a single, existing server.
Transactions

MySQL has long supported ACID-compliant transactions, making it ideal for systems that require strict data consistency.

MongoDB also supports ACID transactions but was originally designed for flexibility and scalability.
Performance

MongoDB can deliver high performance when working with large volumes of unstructured or rapidly changing data because of its flexible document-based structure.

MySQL performs very well with structured data and complex queries, especially when relationships between tables are required.
Durability

MySQL provides strong durability through its ACID-compliant storage engines such as InnoDB.

MongoDB also supports durability by writing operations to its journal, which helps ensure that data is not lost after a crash or restart.
Security

MySQL has strong built-in security features, including user authentication, role-based access control, and permission management that help protect data.

MongoDB also provides security features like authentication and encryption, but in earlier versions these features needed more manual configuration

MongoDB vs MySQL: Which One Should You Use?

MongoDB is a good choice if:

Your application handles large amounts of unstructured or rapidly changing data.
You need a flexible schema that can evolve as your application grows.
Your system requires high scalability or cloud-based deployment.
You are building modern applications such as real-time analytics platforms, mobile apps, or IoT systems.
You want to speed up development.

MySQL is a good choice if:

Your application relies on structured data with a fixed schema.
You need strong data consistency and reliable transactions.
Data Security is your major priority.
You are building traditional systems such as financial, enterprise, or legacy applications
You need strong community support, as MySQL has been around for many years.

Conclusion

MongoDB and MySQL are both powerful database technologies, but they are designed for different types of applications. MongoDB offers a flexible document-based structure that works well for applications handling large volumes of unstructured or rapidly changing data. MySQL, on the other hand, is well suited for systems that rely on structured data, strong relationships between tables, and reliable transactions.

Choosing the right database depends on your project requirements. If your application requires a fixed schema and strong data consistency, MySQL may be the better option. However, if your system needs flexibility, scalability, and the ability to handle evolving data structures, MongoDB can be a strong choice.

DEV Community: Onatade Abdulmajeed

Top 5 Spring Dependency Injection Best Practices You Need

Table of Contents

Introduction

Understanding Dependency Injection

Core Benefits of Using Dependency Injection (DI) in Spring

Common Ways to Use Dependency Injection (DI) in Spring

Best Practices for Effective Dependency Injection.

1. Prefer Constructor Injection

Advantages of Constructor Injection

2. Use @Autowired Wisely

Best Practices for @Autowired

3. Leverage Qualifiers

4. Scope Management

Best Practices for Scope Management

5. Avoid Over-Complexity

Tips for avoiding excessive use of Dependency Injection (DI):

Final Thoughts

Additional Resources

Building an AI Blog Generator with Node.js, OpenAI & Notion MCP

What I Built

Video Demo

GitHub Repository

How I Used Notion MCP

Tech Stack

Key Features

What I Learned

Conclusion

[Boost]

MongoDB vs MySQL: Choosing the Right Database for Your Project

MongoDB vs MySQL: Choosing the Right Database for Your Project

Table of Contents

Introduction

What is MongoDB?

Advantages of MongoDB

Disadvantages of MongoDB

What is MySQL?

Advantages of MySQL

Disadvantages of MySQL

Differences between MongoDB vs MySQL

MongoDB vs MySQL: Which One Should You Use?

Conclusion