Could not autowire. No beans of 'HelloController' type found.

This error typically occurs when Spring cannot find a bean of type 'HelloController' to inject. There are a few possible reasons for this:

1. Check if the 'HelloController' class is properly annotated with the `@Controller` or `@RestController` annotation. This ensures that Spring recognizes it as a bean.

2. Verify that the 'HelloController' class is located within the component scan path. By default, Spring scans for components (including controllers) in the package and its sub-packages where the main application class is located. If the controller is in a different package, you can use the `@ComponentScan` annotation to specify additional packages to scan.

3. Ensure that the 'HelloController' class is being instantiated as a bean. You can use annotations like `@Component`, `@Service`, or `@Repository` to declare it as a bean, depending on its role in your application.

4. Double-check your project's dependencies and make sure you have all the required dependencies for Spring MVC. For example, you should have the `spring-webmvc` dependency in your `pom.xml` file (for Maven) or `build.gradle` file (for Gradle).

If none of these solutions work, please provide more details about your project structure and configuration so that I can assist you further.