Spring Bean Scopes Overview

Direct Answer

A Spring scope controls how a bean instance is obtained and how long the container manages it. singleton is one instance per bean definition per ApplicationContext and is the default. prototype creates a new instance each time the container is asked for that bean. In a web-aware context, request, session, application, and websocket scopes follow their respective web lifetimes.

Code Example

import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Service;
import org.springframework.web.context.annotation.RequestScope;
import org.springframework.web.context.annotation.SessionScope;
import java.util.ArrayList;
import java.util.List;

@Service // default singleton scope
public class OrderService {
    private final OrderRepository repository;
    public OrderService(OrderRepository repository) {
        this.repository = repository;
    }
}

@Service
@Scope("prototype") // a new instance every time
public class ReportGenerator {
    private String reportData; // stateful, so prototype is needed
}

@RequestScope // one instance per HTTP request
public class ShoppingCart {
    private List<String> items = new ArrayList<>();
}

@SessionScope // one instance per user session
public class UserPreferences {
    private String theme;
    private String language;
}

Common Mistakes & Pitfalls

• Forgetting web scopes exist: Freshers often think Spring only has singleton and prototype, missing that request, session, and application scopes exist in web apps.
• Using singleton for stateful beans: Storing user-specific data (like current cart items) in a singleton bean causes one user to see another user's data because the instance is shared across all threads.
• Not using a scoped proxy for web scopes: Injecting a request or session scoped bean into a singleton without proxyMode=TARGET_CLASS fails because Spring can't put a short-lived bean into a long-lived one — you get a BeanCreationException at startup.