ContextLoaderListener: A Necessary Evil or an Unnecessary Complication?

Developers often encounter the use of ContextLoaderListener and DispatcherServlet in Spring web applications. However, a nagging question arises: why not simply use DispatcherServlet to manage all configuration and avoid the complexity of two contexts?

Purpose of ContextLoaderListener and DispatcherServlet

ContextLoaderListener is designed to load non-web-related configurations during the application's startup. Conversely, DispatcherServlet is responsible for handling web-specific elements such as controllers and view resolvers. This division creates two contexts: a parent context handled by ContextLoaderListener and a child context managed by DispatcherServlet.

Why Use Both Instead of Just DispatcherServlet?

Traditionally, this two-context pattern has been recommended for reasons such as isolating non-web dependencies and allowing multiple DispatcherServlets to coexist. However, in recent scenarios, these benefits may not be as relevant.

Arguments for Removing ContextLoaderListener

The absence of multiple DispatcherServlets or the need for non-web dependencies in your current application can make ContextLoaderListener redundant. By consolidating configuration into a single context managed by DispatcherServlet, you simplify the application structure, eliminate potential conflicts between contexts, and streamline troubleshooting.

Caveats

While removing ContextLoaderListener may provide benefits, there are potential drawbacks to consider:

• Missing background tasks: If you rely on background tasks (e.g., scheduled tasks), ensure that DispatcherServlet is correctly configured with load-on-startup to avoid delays in their execution.
• Legacy or non-Spring servlets: If your application integrates with legacy or non-Spring components that depend on the webapp-level context, you may need to maintain ContextLoaderListener.

Conclusion

In the absence of compelling reasons, removing ContextLoaderListener and utilizing a single context can enhance the simplicity and maintainability of your Spring web application. However, carefully evaluate your application's dependencies and consider potential drawbacks before making this transition.