@Scope for bean scope in Spring Boot - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a singleton scoped bean using @Scope.

Spring Boot

@Component
@Scope([1])
public class MyService {}

Drag options to blanks, or click blank then click option'

A"prototype"

B"session"

C"request"

D"singleton"

Attempts:

3 left

💡 Hint

Common Mistakes

Using "prototype" instead of "singleton" for a singleton bean.

The default and most common bean scope is singleton, which means one instance per Spring container.

2fill in blank

medium

Complete the code to define a prototype scoped bean using @Scope.

Spring Boot

@Component
@Scope([1])
public class TaskProcessor {}

Drag options to blanks, or click blank then click option'

A"prototype"

B"application"

C"singleton"

D"session"

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing prototype with singleton scope.

The prototype scope creates a new bean instance every time it is requested.

3fill in blank

hard

Fix the error in the code to set the bean scope to session.

Spring Boot

@Component
@Scope([1])
public class UserSession {}

Drag options to blanks, or click blank then click option'

ASession

Bsession

C"session"

D"Session"

Attempts:

3 left

💡 Hint

Common Mistakes

Missing quotes around the scope name.

The scope value must be a string literal with quotes, like "session".

4fill in blank

hard

Fill both blanks to define a request scoped bean with proxy mode.

Spring Boot

@Component
@Scope(value = [1], proxyMode = [2])
public class RequestBean {}

Drag options to blanks, or click blank then click option'

A"request"

BScopedProxyMode.TARGET_CLASS

C"singleton"

DProxyMode.DEFAULT

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong scope value or proxy mode.

Request scope is specified with "request". Proxy mode ScopedProxyMode.TARGET_CLASS creates a class-based proxy to handle the scope properly.

5fill in blank

hard

Fill all three blanks to define a session scoped bean with proxy mode and a custom bean name.

Spring Boot

@Component("[1]")
@Scope(value = [2], proxyMode = [3])
public class SessionBean {}

Drag options to blanks, or click blank then click option'

AcustomSessionBean

B"session"

CScopedProxyMode.TARGET_CLASS

D"prototype"

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to quote the scope or using wrong proxy mode.

The bean is named customSessionBean, scoped to "session", with proxy mode ScopedProxyMode.TARGET_CLASS for proper session handling.

Practice

1. What does the @Scope("prototype") annotation do in a Spring Boot bean?

easy

A. Creates a new bean instance per HTTP request

B. Creates only one shared instance of the bean for the entire application

C. Creates a new bean instance per HTTP session

D. Creates a new instance of the bean every time it is requested

Solution

1. Step 1: Understand the prototype scope meaning

   The prototype scope means Spring creates a new bean instance each time it is requested from the container.

2. Step 2: Compare with other scopes

   Unlike singleton which shares one instance, prototype always returns a fresh object.

3. Final Answer:

   Creates a new instance of the bean every time it is requested -> Option D

4. Quick Check:

   @Scope("prototype") = new instance each request [OK]

Hint: Prototype means new bean each request, singleton means shared [OK]

Common Mistakes:

• Confusing prototype with singleton scope
• Thinking prototype beans are shared
• Mixing prototype with web scopes like session or request

2. Which of the following is the correct way to declare a singleton scoped bean using @Scope annotation in Spring Boot?

easy

A. @Scope("session")

B. @Scope("prototype")

C. @Scope("singleton")

D. @Scope("request")

Solution

1. Step 1: Recall default and explicit singleton scope

   Singleton is the default scope in Spring, but explicitly it is declared as @Scope("singleton").

2. Step 2: Verify other scopes

   prototype creates new instances, session and request are web scopes, not singleton.

3. Final Answer:

   @Scope("singleton") -> Option C

4. Quick Check:

   Singleton scope = @Scope("singleton") [OK]

Hint: Singleton scope is default but use @Scope("singleton") explicitly [OK]

Common Mistakes:

• Using @Scope("prototype") for singleton beans
• Confusing web scopes with singleton
• Omitting @Scope and expecting prototype behavior

3. Consider this Spring Boot bean declaration:

@Component
@Scope("request")
public class UserRequestBean { }

What happens when this bean is injected into two different HTTP requests?

medium

A. Each request gets a new bean instance

B. Both requests share the same bean instance

C. Only the first request gets a bean, others get null

D. Bean is created once per session, shared across requests

Solution

1. Step 1: Understand request scope behavior

   The request scope means Spring creates a new bean instance for each HTTP request.

2. Step 2: Apply to two different requests

   Since the requests are different, each gets its own separate bean instance.

3. Final Answer:

   Each request gets a new bean instance -> Option A

4. Quick Check:

   @Scope("request") = new bean per HTTP request [OK]

Hint: Request scope means new bean per HTTP request [OK]

Common Mistakes:

• Assuming request scope shares bean across requests
• Confusing request scope with session scope
• Thinking request scope behaves like singleton

4. Given this bean declaration:

@Component
@Scope("session")
public class ShoppingCart { }

What is the likely error if you try to inject this bean into a singleton scoped bean without special handling?

medium

A. No error, injection works normally

B. Runtime error due to incompatible scopes

C. Compilation error due to missing @Scope annotation

D. Bean is created once and shared across all sessions

Solution

1. Step 1: Understand scope mismatch problem

   Injecting a session-scoped bean into a singleton bean causes a scope mismatch because singleton lives longer than session beans.

2. Step 2: Result of mismatch without proxy

   Without proxy or special configuration, Spring throws a runtime error as it cannot inject a shorter-lived bean into a longer-lived one safely.

3. Final Answer:

   Runtime error due to incompatible scopes -> Option B

4. Quick Check:

   Session bean into singleton without proxy = runtime error [OK]

Hint: Injecting shorter scope bean into singleton causes runtime error [OK]

Common Mistakes:

• Assuming injection always works regardless of scope
• Ignoring need for proxyMode in such injections
• Confusing compilation and runtime errors

5. You want a Spring Boot bean to create a new instance for each HTTP session but share the same instance within that session. Which @Scope annotation and configuration should you use?

hard

A. @Scope(value = "session", proxyMode = ScopedProxyMode.TARGET_CLASS)

B. @Scope("prototype")

C. @Scope("singleton")

D. @Scope(value = "request", proxyMode = ScopedProxyMode.INTERFACES)

Solution

1. Step 1: Identify session scope for per-session bean

   The session scope creates one bean instance per HTTP session, which fits the requirement.

2. Step 2: Use proxyMode for injection into singleton beans

   Adding proxyMode = ScopedProxyMode.TARGET_CLASS allows safe injection into other beans by creating a proxy that resolves the correct session instance.

3. Final Answer:

   @Scope(value = "session", proxyMode = ScopedProxyMode.TARGET_CLASS) -> Option A

4. Quick Check:

   Session scope + proxyMode = new instance per session shared inside session [OK]

Hint: Use session scope with proxyMode for per-session shared bean [OK]

Common Mistakes:

• Using prototype scope which creates new instance every injection
• Using singleton scope which shares one instance globally
• Using request scope which creates new instance per HTTP request