In a Spring MVC application, there are typically two contexts: the root application context and the web application context.

1. Root Application Context: This context is loaded by the ContextLoaderListener when the application starts up. It contains beans that are shared among all servlets in the application. Typically, beans related to business logic, services, repositories, data access, and other non-web components are defined in the root application context. These beans are initialized when the application starts up and remain in memory throughout the application’s lifecycle.

2. Web Application Context: This context is specific to the DispatcherServlet and is loaded when the DispatcherServlet is initialized. It contains beans that are scoped to the web layer, such as controllers, view resolvers, handler mappings, and other web-related components. Each DispatcherServlet has its own web application context. Beans defined in the web application context are typically specific to handling web requests and responses.

So, why would you use the root application context instead of a web application context?

• Sharing Beans: If you have beans that are used across multiple servlets or components in your application, it’s best to define them in the root application context. This allows these beans to be shared among different parts of the application without duplication.

• Global Configuration: Beans that are not specific to handling web requests, such as business services, database access objects, and other infrastructure components, belong in the root application context. Placing them here ensures that they are initialized once when the application starts up and remain available throughout its lifecycle.

• Testability: Beans defined in the root application context are easier to test in isolation since they are not tied to the web layer. This makes it simpler to write unit tests for business logic and other non-web components.

• Scalability: Separating non-web components into the root application context can help improve the scalability and maintainability of your application. It makes it easier to modularize and organize your codebase, especially as the application grows in size and complexity.

Spring root application context helps to promote better organization, reusability, and maintainability of your application code.