In web development with Spring Boot, encountering a "404 Not Found" error is relatively common, especially when dealing with Spring Boot MVC (Model-View-Controller) applications. Such an error indicates that the server could not find the requested resource. This guide analyzes the possible causes and solutions for a Spring Boot MVC Template not loading and throwing a 404 Not Found error.

Understanding the 404 Error in Spring Boot MVC

A 404 error is an HTTP status code that means the server could not find the requested resource. Within a Spring Boot MVC application, this typically signifies that a mapped URL does not correspond to any controller, resource, or endpoint as defined in the application.

Common Causes of 404 Not Found Error

1. Incorrect Request Mapping:
   • Ensure that the URL path used in the browser matches the path defined in the @RequestMapping or annotation-specific mappings like @GetMapping, @PostMapping, etc.
2. Thymeleaf or JSP Template Issues:
   • The template engine (like Thymeleaf) could be misconfigured, causing Spring Boot to fail when trying to load views.
3. Static Resources Misconfiguration:
   • Static assets (CSS, JS, images) might not be served correctly. If not specified, Spring Boot uses src/main/resources/static as the default location for static content.
4. Controller Not Scanned:
   • Annotations like @RestController or @Controller might be missing, or the components are not being scanned by Spring Boot due to misconfiguration.
5. Incorrect File Structure:
   • Files structures, such as incorrect package design or improper location of Controllers and view directories, can contribute to navigation failures in the web application.

Example Scenario

Consider a simple Spring Boot application where a controller is supposed to load a view from a Thymeleaf template.

• The browser URL should be /home. Check if there are no extra characters or slashes.
• Ensure the template home.html is available under src/main/resources/templates/.
• If static resources are needed, ensure they exist under src/main/resources/static/.
• The main application class should be annotated properly and reside under the base package or sub-package structure for scanning:
• Check Server Logs:
• Application Profile Configuration:
• Cross-Referencing with API Docs:
• Dependencies & Build Configuration: