Can a situation occur where the controller is absent in the context?

Yes, it might.

The reasons could be:

1. Absence of @Controller or @RestController annotation. Spring does not scan classes without the appropriate annotation.
2. Incorrect package scanning configuration. If the package containing the controller is not included in the scan list (for example, in @ComponentScan or XML configuration), Spring will not find it.
3. Errors during context startup. If errors occur during context initialization, some components, including controllers, may not be added.
4. Use of @Conditional annotations that prevent the creation of the controller bean based on certain conditions.
5. Dependency issues with the controller. If the controller depends on a bean that cannot be created or found, Spring may not create the controller itself.

Example of incorrect package scanning configuration:

// In this case, the controller in the package com.example.controllers will be ignored
@Configuration
@ComponentScan(basePackages = "com.example.services")
public class AppConfig {
    // ...
}