Bean Scopes

1. Scope Categories

• singleton: every time the Bean is obtained from the container, it is the same instance.
• prototype: every time the Bean is obtained from the container, a new one is created.
• request: the same Bean is used within an HTTP request.
• session: the same Bean is used within an HTTP session.

2. Why Is There prototype?

• Modifying properties on a singleton can cause thread-safety problems.

For example:

@Autowired
HttpServletRequest request;

The injected HttpServletRequest here does not have a thread-safety problem because it is prototype-scoped.

2.1. How to Use prototype

• MainController

@RestController
public class MainController
{
    @Autowired
    MainServices services;
}

• MainServices

@Service
@Scope(value="prototype", proxyMode=ScopedProxyMode.TARGET_CLASS)// ScopedProxyMode.TARGET_CLASS is required here.
public class MainServices
{
//...
}

3. References

• Correct Usage of Spring Beans with prototype Scope - Zhihu