@EnableCaching annotation in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What happens when @EnableCaching is added to a Spring Boot application?

Consider a Spring Boot application with a service method annotated with @Cacheable. What is the effect of adding @EnableCaching to the main configuration class?

Spring Boot

import org.springframework.cache.annotation.EnableCaching;
import org.springframework.context.annotation.Configuration;

@Configuration
@EnableCaching
public class AppConfig {
}

A It automatically creates a cache store but does not enable caching on any methods.

B It disables all caching in the application, forcing methods to always execute fully.

C It activates Spring's annotation-driven cache management, enabling caching behavior on methods annotated with @Cacheable.

D It only enables caching for methods annotated with @CachePut, ignoring @Cacheable annotations.

💡 Hint

Think about what @EnableCaching does in relation to @Cacheable methods.

The @EnableCaching annotation tells Spring to look for caching annotations like @Cacheable and activate caching behavior on those methods. Without it, caching annotations are ignored.

📝 Syntax

intermediate

Identify the correct way to enable caching in a Spring Boot application

Which of the following code snippets correctly enables caching in a Spring Boot application?

A

@Configuration
@EnableCaching
public class CacheConfig {}

B

@EnableCaching
public class CacheConfig {}

C

@Configuration
@EnableCache
public class CacheConfig {}

D

@Configuration
@EnableCaching(true)
public class CacheConfig {}

💡 Hint

Remember the exact annotation name and required annotations for configuration classes.

The @EnableCaching annotation must be used on a class annotated with @Configuration to enable caching properly. @EnableCache does not exist and @EnableCaching does not take parameters.

🔧 Debug

advanced

Why does caching not work despite @EnableCaching being present?

Given the following code, why might caching not be working as expected? @Configuration @EnableCaching public class AppConfig {} @Service public class MyService { @Cacheable("items") public String getItem(String id) { return "Item" + id; } } Assume the application runs but caching does not reduce method calls.

A The @EnableCaching annotation must be placed on the service class, not the configuration class.

B The cache name "items" is invalid and must be registered explicitly in the cache manager.

C The @Cacheable annotation requires a key attribute to work properly.

D The service method is called from within the same class, so Spring's proxy does not intercept the call to apply caching.

💡 Hint

Think about how Spring proxies work and when caching applies.

Spring caching works through proxies. If a method annotated with @Cacheable is called from within the same class, the proxy is bypassed and caching does not occur.

🧠 Conceptual

advanced

What is the role of @EnableCaching in Spring's caching abstraction?

Which statement best describes the role of @EnableCaching in a Spring application?

A @EnableCaching disables caching unless a custom cache manager bean is provided.

B @EnableCaching activates the processing of caching annotations and configures a cache manager if none is defined.

C @EnableCaching replaces the need to annotate methods with @Cacheable or other caching annotations.

D @EnableCaching automatically creates and manages all caches without any further configuration.

💡 Hint

Consider what enabling caching means for annotation processing and cache manager setup.

@EnableCaching enables Spring to detect caching annotations and sets up a default cache manager if none is provided. It does not create caches automatically nor replace caching annotations.

❓ state_output

expert

What is the output count of method calls with @EnableCaching and @Cacheable?

Given this Spring Boot service: @Service public class CounterService { private int count = 0; @Cacheable("numbers") public int getNumber(int input) { count++; return input * 2; } public int getCount() { return count; } } And this test code: CounterService service = context.getBean(CounterService.class); service.getNumber(5); service.getNumber(5); service.getNumber(10); service.getNumber(5); int calls = service.getCount(); What is the value of calls after these calls if @EnableCaching is present?

A 2

B 1

C 4

D 3

💡 Hint

Remember that @Cacheable caches results by method parameters.

The method is called with inputs 5, 5, 10, 5. The first call with 5 executes and increments count. The second call with 5 returns cached result, no increment. The call with 10 executes and increments count. The last call with 5 returns cached result again. So count increments twice.

Practice

1. What is the main purpose of the @EnableCaching annotation in a Spring Boot application?

easy

A. To activate caching support so methods annotated with @Cacheable can cache results

B. To disable all caching mechanisms in the application

C. To configure database connections automatically

D. To enable security features for REST endpoints

Solution

1. Step 1: Understand @EnableCaching role

   This annotation activates Spring's caching support, allowing caching annotations to work.

2. Step 2: Connect with @Cacheable

   Methods annotated with @Cacheable store their results in cache only if caching is enabled.

3. Final Answer:

   To activate caching support so methods annotated with @Cacheable can cache results -> Option A

4. Quick Check:

   @EnableCaching enables caching [OK]

Hint: Remember: @EnableCaching turns caching ON [OK]

Common Mistakes:

• Thinking @EnableCaching disables caching
• Confusing it with database or security annotations
• Assuming it caches data by itself without @Cacheable

2. Which of the following is the correct way to enable caching in a Spring Boot application?

easy

A. @CacheEnable

B. @EnableCache

C. @EnableCaching

D. @CachingEnable

Solution

1. Step 1: Recall the exact annotation name

   The correct annotation to enable caching is @EnableCaching.

2. Step 2: Check other options for typos

   Options B, C, and D are incorrect because they are not valid Spring annotations.

3. Final Answer:

   @EnableCaching -> Option C

4. Quick Check:

   Correct annotation spelling is @EnableCaching [OK]

Hint: Look for exact spelling: EnableCaching, not EnableCache [OK]

Common Mistakes:

• Using incorrect annotation names with similar words
• Missing the capital 'C' in Caching
• Confusing with other Spring annotations

3. Given the following Spring Boot code snippet, what will be the output when getData() is called twice?

@EnableCaching
@Service
public class DataService {
  private int count = 0;

  @Cacheable("dataCache")
  public String getData() {
    count++;
    return "Call number: " + count;
  }
}

medium

A. ["Call number: 1", "Call number: 1"]

B. ["Call number: 2", "Call number: 2"]

C. ["Call number: 0", "Call number: 1"]

D. ["Call number: 1", "Call number: 2"]

Solution

1. Step 1: Understand caching effect on method calls

   The first call to getData() runs the method, increments count to 1, and caches the result.

2. Step 2: Analyze second call behavior

   The second call returns the cached result without running the method again, so count stays 1.

3. Final Answer:

   ["Call number: 1", "Call number: 1"] -> Option A

4. Quick Check:

   Cache returns same result on repeated calls [OK]

Hint: Cached method runs once; repeated calls return cached result [OK]

Common Mistakes:

• Assuming count increments on every call despite caching
• Ignoring that @Cacheable caches method output
• Confusing cache key usage

4. Identify the error in the following Spring Boot configuration that prevents caching from working:

@Configuration
public class CacheConfig {
  @Bean
  public CacheManager cacheManager() {
    return new ConcurrentMapCacheManager("items");
  }
}

medium

A. Cache name "items" is invalid

B. Missing @EnableCaching annotation on configuration class

C. CacheManager bean should return null

D. CacheManager must be annotated with @Service

Solution

1. Step 1: Check caching activation

   Defining a CacheManager bean is not enough; caching must be enabled with @EnableCaching.

2. Step 2: Verify other options

   CacheManager returning null or invalid cache names are incorrect; @Service is unrelated here.

3. Final Answer:

   Missing @EnableCaching annotation on configuration class -> Option B

4. Quick Check:

   Enable caching with @EnableCaching [OK]

Hint: Always add @EnableCaching to activate caching [OK]

Common Mistakes:

• Forgetting to add @EnableCaching annotation
• Misunderstanding CacheManager bean role
• Wrong annotation usage on CacheManager

5. You want to cache results of a method that takes a user ID and returns user details. You also want to clear the cache when user data updates. Which combination of annotations and configuration correctly achieves this in Spring Boot?

hard

A. Use @EnableCaching on service class, @CachePut("users") on get method, and no annotation on update method

B. Use @CacheEvict on config class, @EnableCaching on update method, and no caching on get method

C. Use @Cacheable("users") on config class, @EnableCaching on get method, and @CacheEvict on update method

D. Use @EnableCaching on config class, @Cacheable("users") on get method, and @CacheEvict(value = "users", key = "#userId") on update method

Solution

1. Step 1: Enable caching globally

   Add @EnableCaching on a configuration or main class to activate caching support.

2. Step 2: Cache method results and evict on update

   Use @Cacheable("users") on the method fetching user details to cache results. Use @CacheEvict(value = "users", key = "#userId") on the update method to clear cache for that user.

3. Final Answer:

   Use @EnableCaching on config class, @Cacheable("users") on get method, and @CacheEvict(value = "users", key = "#userId") on update method -> Option D

4. Quick Check:

   Enable caching + cache get + evict on update [OK]

Hint: Enable caching, cache gets, evict on updates [OK]

Common Mistakes:

• Not enabling caching globally with @EnableCaching
• Using @CachePut instead of @CacheEvict for clearing cache
• Placing annotations on wrong classes or methods