@Profile for environment-specific beans in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What bean is loaded with active profile 'dev'?

Given these two Spring beans with @Profile annotations, which bean will be loaded when the active profile is set to 'dev'?

Spring Boot

import org.springframework.context.annotation.Profile;
import org.springframework.stereotype.Component;

@Component
@Profile("dev")
public class DevService {
    public String getName() { return "Development Service"; }
}

@Component
@Profile("prod")
public class ProdService {
    public String getName() { return "Production Service"; }
}

A Both DevService and ProdService beans are loaded.

B ProdService bean is loaded and DevService is ignored.

C DevService bean is loaded and ProdService is ignored.

D No beans are loaded because profiles conflict.

💡 Hint

Think about how @Profile controls bean loading based on active profiles.

The @Profile annotation tells Spring to load a bean only if the specified profile is active. Since the active profile is 'dev', only the DevService bean is loaded. The ProdService bean is ignored because its profile 'prod' is not active.

📝 Syntax

intermediate

Which @Profile annotation syntax is correct?

Which option shows the correct way to use @Profile to specify multiple profiles for a bean in Spring Boot?

A @Profile(dev | test)

B @Profile({"dev", "test"})

C @Profile(dev, test)

D @Profile("dev, test")

💡 Hint

Check how arrays are passed in Java annotations.

The correct syntax to specify multiple profiles is to pass an array of strings: @Profile({"dev", "test"}). Other options are either invalid Java syntax or incorrect usage.

🔧 Debug

advanced

Why does this bean not load despite active profile?

Given this bean definition and active profile 'prod', why does Spring fail to load the bean?

Spring Boot

import org.springframework.context.annotation.Profile;
import org.springframework.stereotype.Component;

@Component
@Profile("production")
public class PaymentService {
    // service code
}

A Because the active profile is 'prod' but the bean is annotated with 'production'.

B Because @Component is missing.

C Because the class is not public.

D Because @Profile cannot be used on classes.

💡 Hint

Check if the profile names match exactly.

The active profile is 'prod' but the bean is annotated with @Profile("production"), which does not match. Profile names must match exactly for the bean to load.

❓ state_output

advanced

What is the output when no active profile is set?

Consider these two beans with @Profile annotations. What happens if no active profile is set in the Spring Boot application?

Spring Boot

import org.springframework.context.annotation.Profile;
import org.springframework.stereotype.Component;

@Component
@Profile("dev")
public class DevConfig {
    public String getConfig() { return "Dev Config"; }
}

@Component
@Profile("prod")
public class ProdConfig {
    public String getConfig() { return "Prod Config"; }
}

A Only ProdConfig bean is loaded by default.

B Both DevConfig and ProdConfig beans are loaded.

C Only DevConfig bean is loaded by default.

D Neither DevConfig nor ProdConfig beans are loaded.

💡 Hint

Think about what happens when no profile is active and beans require profiles.

Beans annotated with @Profile are only loaded if their profile is active. If no profile is active, none of these beans load.

🧠 Conceptual

expert

How to load a bean for all profiles except 'test'?

Which @Profile expression correctly loads a bean for all profiles except 'test' in Spring Boot?

A @Profile("!test")

B @Profile("all & !test")

C @Profile("!test") and @Profile("*")

D @Profile("!test") and @Profile("default")

💡 Hint

Spring supports negation in @Profile expressions.

The @Profile annotation supports negation with !. Using @Profile("!test") loads the bean for all profiles except 'test'. Other options are invalid or unsupported syntax.

Practice

1. What is the main purpose of the @Profile annotation in Spring Boot?

easy

A. To define the database connection URL

B. To schedule tasks at fixed intervals

C. To create beans only for specific environments

D. To handle HTTP requests in controllers

Solution

1. Step 1: Understand the role of @Profile

   The @Profile annotation is used to mark beans that should only be created when a specific environment profile is active.

2. Step 2: Compare with other options

   Options A, C, and D relate to other Spring Boot features but not to environment-specific bean creation.

3. Final Answer:

   To create beans only for specific environments -> Option C

4. Quick Check:

   @Profile controls bean creation per environment [OK]

Hint: Remember: @Profile controls which beans load per environment [OK]

Common Mistakes:

• Confusing @Profile with @Component or @Service
• Thinking @Profile sets database URLs
• Assuming @Profile schedules tasks

2. Which of the following is the correct way to use @Profile on a Spring bean class for the "dev" environment?

easy

A. @Profile("dev")
public class DevService {}

B. @Profile(dev)
public class DevService {}

C. @Profile({dev})
public class DevService {}

D. @Profile(["dev"])
public class DevService {}

Solution

1. Step 1: Check correct syntax for @Profile

   The @Profile annotation requires a string value in quotes, e.g., @Profile("dev").

2. Step 2: Analyze each option

   @Profile(["dev"]) public class DevService {} uses square brackets, invalid Java annotation syntax. @Profile(dev) public class DevService {} misses quotes around "dev", syntax error. @Profile({dev}) public class DevService {} uses braces but misses quotes around "dev", syntax error. @Profile("dev") public class DevService {} uses correct quoted string syntax.

3. Final Answer:

   @Profile("dev") public class DevService {} -> Option A

4. Quick Check:

   @Profile needs quoted string [OK]

Hint: Use quotes around profile names in @Profile [OK]

Common Mistakes:

• Omitting quotes around profile names
• Using square brackets instead of curly braces
• Confusing array syntax with string

3. Given the following Spring Boot configuration and beans, what will be the output when the active profile is set to "prod"?

@Profile("dev")
@Component
public class DevBean {
    public String getMessage() { return "Development Bean"; }
}

@Profile("prod")
@Component
public class ProdBean {
    public String getMessage() { return "Production Bean"; }
}

@Component
public class BeanUser {
    private final Object bean;
    public BeanUser(@Autowired(required = false) Object bean) { this.bean = bean; }
    public String show() { return bean == null ? "No Bean" : ((ProdBean)bean).getMessage(); }
}

medium

A. Development Bean

B. Production Bean

C. ClassCastException at runtime

D. No Bean

Solution

1. Step 1: Identify active profile and beans created

   With profile "prod" active, only ProdBean is created. DevBean is not created.

2. Step 2: Analyze BeanUser constructor injection

   BeanUser tries to autowire an Object bean with @Autowired(required = false). Spring injects the available ProdBean instance as it matches.

3. Step 3: Check the show() method

   In show(), bean is cast to ProdBean, which succeeds, returning "Production Bean".

4. Final Answer:

   Production Bean -> Option B

5. Quick Check:

   Prod profile loads ProdBean successfully [OK]

Hint: Profile determines available beans for injection [OK]

Common Mistakes:

• Thinking Object type causes injection failure
• Expecting ClassCastException with matching profile
• Confusing which beans load per profile

4. You have two beans annotated with @Profile("test") and @Profile("prod") respectively. When running the app with no active profile set, you get a NoSuchBeanDefinitionException. What is the most likely cause?

medium

A. The beans are not annotated with @Component

B. The beans have syntax errors in @Profile annotation

C. Spring Boot does not support @Profile annotation

D. No profile is active, so no beans with @Profile are created

Solution

1. Step 1: Understand @Profile behavior with no active profile

   If no profile is active, Spring does not create beans annotated with any specific profile.

2. Step 2: Analyze exception cause

   NoSuchBeanDefinitionException means Spring could not find a bean to inject because none were created due to missing active profile.

3. Final Answer:

   No profile is active, so no beans with @Profile are created -> Option D

4. Quick Check:

   No active profile means no profile-specific beans [OK]

Hint: Beans with @Profile need active profile to load [OK]

Common Mistakes:

• Assuming beans load without active profile
• Blaming syntax errors without checking profiles
• Ignoring need for @Component on beans

5. You want to create a bean that is active in both "dev" and "test" profiles but not in "prod". Which @Profile annotation usage correctly achieves this?

hard

A. @Profile({"dev", "test"})

B. @Profile("dev & test")

C. @Profile("dev | test")

D. @Profile({"dev & test"})

Solution

1. Step 1: Understand @Profile multiple values usage

   Using @Profile({"dev", "test"}) means the bean is active if either "dev" OR "test" profile is active.

2. Step 2: Analyze other options

   @Profile("dev & test") and D use string with "&" which is invalid syntax for multiple profiles. @Profile("dev | test") uses "|" inside string which is not supported syntax.

3. Final Answer:

   @Profile({"dev", "test"}) -> Option A

4. Quick Check:

   Use array of profiles for OR condition in @Profile [OK]

Hint: Use array syntax for multiple profiles in @Profile [OK]

Common Mistakes:

• Using string with & or | inside @Profile
• Confusing AND and OR logic in profiles
• Forgetting to use curly braces for multiple profiles