IOC (Inversion of Control) and Application Context

In traditional Java applications, we used to manually create objects of a class using the new operator. This meant that we were responsible for managing the object lifecycle and dependencies within our code.

However, in a Spring Boot application, we delegate the responsibility of object creation and management to the Spring framework. Instead of manually instantiating objects, we let Spring create and manage them through Dependency Injection (DI). This process is known as Inversion of Control (IoC), where the control over object creation is transferred from the developer to the Spring container.

By doing this, Spring ensures better loose coupling, scalability, and easier dependency management within the application.

The process used by Inversion of Control (IoC) to create and manage objects is interchangeably referred to as the Application Context in Spring.

ApplicationContext or IoC is the core container in Spring responsible:
1. To manage bean life cycle including creation, managing and configuring Beans
2. Manage Dependency Injection (DI)
3. Application configuration

Spring provides two types of containers:

BeanFactory Container

A lightweight container, primarily used for simple dependency injection.

BeanfactoryContainer class is an implementation of org.springframework.beans.factory.BeanFactory interface.
Below is the code snippet to create BeanFactory instance:

Resource resource=new ClassPathResource(“applicationContext.xml”);
BeanFactory factory=new XmlBeanFactory(resource);

ApplicationContext Container

A more advanced container, recommended for most Spring applications.

ApplicationContext is the child interface of BeanFactory interface.

ClassPathXmlApplicationContext class is an implementation of org.springframework.context.ApplicationContext interface.

Below is the code snippet to create BeanFactory instance:

ApplicationContext context =
new ClassPathXmlApplicationContext(“applicationContext.xml”)