Spring’s default bean scope is singleton, where a single instance is created per container and shared across all request. The framework supports several scopes to manage bean lifecycle and visibility.

• Singleton: The default scope; one instance per Spring IoC container.
• Prototype: A new insatnce is created on each request.
• Request: Exclusive to web applications; a new instance per HTTP request, valid only for that request.
• Session: Exclusive to web applications; a new instance per HTTP session, valid for the session’s duration.
• Application: Exclusive to web applications; one instance per ServletContext, shared across the entire application.
• WebSocket: Exclusive to web applications; an instance is tied to a WebSocket’s lifecycle.

To specify a non-default scope, use the scope attribute in @Bean or @Scope annotations:

@Bean
@Scope("prototype")
public DataProcessor dataProcessor() {
    return new DataProcessorImpl();
}

Here, dataProcessor is prototype-scoped, so each injection or getBean() call yields a new DataProcessorImpl instance.

Singleton

A singleton bean is instantiated once per container:

@Configuration
public class AppConfig {
    @Bean
    @Scope("singleton") // Optional, as it is default
    public LoggerService loggerService() {
        return new LoggerServiceImpl();
    }
}

Multiple calls to loggerService() return the same LoggerServiceImpl instance.

Prototype

Each request creates a new prototype bean:

@Configuration
public class AppConfig {
    @Bean
    @Scope("prototype")
    public CacheManager cacheManager() {
        return new CacheManagerImpl();
    }
}

Every retrieval of cacheManager produces a fresh CacheManagerImpl.

Request

In web contexts, a request-scoped bean is created per HTTP request:

@Controller
@Scope("request")
public class RequestHandler {
    // Bean valid only for the current request
}

Session

A session-scoped bean is tied to an HTTP session:

@Component
@Scope("session")
public class SessionData {
    // Instance persists for the user’s session
}

Application

Application-scoped beans are singleton-like with in a ServletContext:

@Component
@Scope("application")
public class AppConfigData {
    // Shared across the entire web application
}

WebSocket

WebSocket-scoped beans align with WebSocket lifecycle events:

@Component
@Scope("websocket")
public class SocketSession {
    // Created per WebSocket connection and destroyed on close
}

For web-specific scopes (request, session, application), ensure Spring’s web modules are configured, such as via ContextLoaderListener in web.xml or Spring Boot auto-configuration.