Introduction to Spring and Spring Boot

The Spring Framework is a popular, open-source framework for Java that helps developers create large, complex applications more easily. It is built around two main ideas: Inversion of Control (IoC) and Dependency Injection (DI). These concepts make code more organized, easier to manage, and simpler to reuse.

Spring Boot is an extension of the Spring Framework designed to make building Spring applications quicker and simpler. It provides a lot of default settings and dependencies, which means developers don’t have to write repetitive setup code and can focus more on the actual business logic of their applications.

Because of its simplicity, flexibility, and strength, Spring Boot is widely used in the industry. Many well-known companies, like Netflix, Target, and Alibaba, use Spring Boot to build and run their applications

• Faster Development

  Spring Boot comes with pre-configured settings and features that automatically handle many of the setup tasks for you. This reduces the amount of repetitive setup code (boilerplate code) developers have to write. As a result, developers can spend more time building the actual features of the application, which speeds up the development process.

• Simplified Configuration

  Configuring a Spring Boot application is straightforward and user-friendly. It simplifies managing all the settings and configuration files needed for the application, making the setup process easier and less error-prone.

• Embedded Server

  Spring Boot includes an embedded web server like Tomcat or Jetty. This means you can run and test your applications on your computer without needing to set up a separate server. This saves time and makes it easier to develop and test applications.

• Modular Architecture

  Spring Boot allows developers to pick and choose which components they need for their project. This means you can create lightweight applications that include only the necessary features, giving you greater flexibility and control over your project.

• Cloud Support

  Spring Boot makes it easy to deploy applications to cloud platforms like AWS, Google Cloud, and Microsoft Azure. This out-of-the-box support means you can quickly move your application to the cloud without extensive setup.

• Large Community

  Spring Boot has a big and active community of developers and users. This means there are plenty of resources available, such as documentation, forums, and tutorials. It’s easy to find help, learn new things, and stay up-to-date with the latest practices and solutions.

Spring and Spring Boot are both popular frameworks for building Java applications, but they have some key differences:

• Configuration

  In Spring, you have to manually set up everything, like the server and dependencies. Spring Boot, however, provides automatic setup and pre-configured dependencies, which saves time and effort.

• Convention over Configuration

  Spring Boot uses a “Convention over Configuration” approach, meaning it provides sensible defaults so you don’t have to configure everything manually. This makes development faster and easier.

• Ease of Use

  Spring Boot is designed to be easy and quick to use, offering features like an embedded web server and automatic configurations. Spring requires more manual setup.

• Dependency Management

  Spring Boot simplifies managing dependencies by offering a set of pre-configured libraries. In contrast, with Spring, you have to manage dependencies on your own.

• Scope

  Spring is a comprehensive framework that supports many functionalities, like dependency injection and data access. Spring Boot is more focused on making web development quicker and easier.

Dependency Injection (DI) is a software design pattern that manages how objects in a program are created and interact with each other. Rather than a class being responsible for creating its dependencies, those dependencies are provided to it. This means the creation of dependent objects happens outside the class and these objects are supplied to the class at runtime, not at compile time.

For example, imagine a car needing an engine to function. Instead of the car building its engine, we give the car an engine when it’s constructed. This way, the car only focuses on its own functionality, and the engine can be reused or swapped if necessary. DI works similarly: components (like the car) receive what they need (like the engine) from external sources.

How Does Spring Help with Dependency Injection?

In previous examples, we might have manually implemented dependency injection through code, explicitly creating and injecting dependencies into our objects. However, Spring Framework can handle this automatically, making it easier and cleaner to manage dependencies. This is one of the main reasons developers turn to Spring for building their applications.

Spring takes over the job of providing dependencies, leaving you to focus on writing business logic. With Spring, you don’t have to worry about manually wiring together objects—Spring does it for you.

How Spring Performs Dependency Injection

Spring uses a software component known as the Inversion of Control (IoC) Container to handle dependency injection. The IoC container manages the life cycle of Spring beans (the objects in Spring) and the injection of their dependencies.

Inversion of Control (IoC) is a software design principle where the control over certain operations (like creating objects or managing dependencies) is transferred from the program to an external container or framework.

Examples of IoC

JVM: Just like the Java Virtual Machine (JVM) is responsible for executing Java programs, Spring’s IoC container is responsible for managing the objects in a Spring application.

Servlet Container: A servlet container executes servlets in a Java web application, similar to how the Spring container manages Spring beans.

By using IoC, we allow the Spring Framework to handle the creation, configuration, and management of the objects and their dependencies in our application.

The Role of the Spring IoC Container

The Spring IoC container is the heart of the Spring Framework. It manages the complete life cycle of Spring beans:

• Instantiation: The IoC container creates the beans.

• Configuration: It configures beans according to the provided metadata (e.g., XML, annotations).

• Initialization: It performs any initialization steps required by the bean.

• Lifecycle Management: The container manages the entire life cycle, including initialization and destruction.

• Dependency Injection: The container automatically injects the required dependencies into the beans.

• Resource Management: It handles connections to databases, APIs, security, and other resources, ensuring efficient management.

Types of Spring IoC Containers

There are two primary types of IoC containers in Spring:

• BeanFactory: The older IoC container in Spring, located in org.springframework.beans.factory. While still usable, it is considered outdated.

• ApplicationContext: The modern, more powerful IoC container that extends the BeanFactory interface. It is located in org.springframework.context and offers additional features such as event propagation, declarative mechanisms to create beans, and integration with Spring’s AOP (Aspect-Oriented Programming) features.