What is a Spring bean?
A Spring bean is an object that the Spring container creates, configures, and manages for you. You mark a class as a bean with annotations like Component, Service, or Bean, and Spring keeps it in its application context ready to inject where needed. By default beans are singletons, meaning one shared instance per container.
- A Spring bean is an object that the Spring container creates, wires, and manages.
- Beans are usually defined by annotations like Component or by methods marked Bean.
- The container handles a bean's full lifecycle, from creation to destruction.
How a bean is created
@Component
class EmailService { }
// or from a configuration method
@Bean
EmailService emailService() { return new EmailService(); }Common bean scopes
- Singleton: one shared instance per container, the default.
- Prototype: a new instance every time it is requested.
- Request and session: one per web request or user session.
Be ready for the scope question. Say the default is singleton, one shared instance, and use prototype when you need a fresh object each time. Knowing that singleton is the default catches a common misconception.
Frequently asked questions
What is the default scope of a bean?
The default scope is singleton, meaning the container creates one shared instance per application context and reuses it everywhere it is injected.
How does a class become a bean?
By annotating it with a stereotype like Component, Service, or Repository and letting component scanning find it, or by defining it with a Bean method.
Common follow up questions
Related interview questions
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