@Autowired, @Primary, and @Qualifier.

Collision Handling:

When multiple beans of the same type exist and you try to @Autowired one, Spring will throw a NoUniqueBeanDefinitionException.

Solutions:

1. @Primary: Marks one bean as the default choice.
2. @Qualifier("name"): Explicitly specifies which bean to inject by its ID/Name.
3. Naming Convention: If you name your variable the same as the bean ID, Spring uses that to resolve the dependency (less reliable than Qualifiers).