@CachePut for updating cache in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What happens when a method annotated with @CachePut is called?

Consider a Spring Boot method annotated with @CachePut. What is the behavior when this method is executed?

A The method executes but does not update the cache.

B The method does not execute; the cached value is returned directly.

C The cache is cleared before the method executes.

D The method executes and updates the cache with the returned value without skipping the method execution.

💡 Hint

Think about whether the method runs or if the cache is just read.

@CachePut always runs the method and then updates the cache with the new result. It does not skip method execution like @Cacheable.

📝 Syntax

intermediate

Which @CachePut annotation syntax correctly updates cache named 'users' with key 'user.id'?

Choose the correct @CachePut annotation syntax to update the cache named users using the id property of the user parameter as the key.

A @CachePut(value = "users", key = "user.id")

B @CachePut(value = "users", key = "#user.id")

C @CachePut(cacheNames = "users", key = "user.id")

D @CachePut(cacheNames = "users", key = "#user")

💡 Hint

Remember to use SpEL (Spring Expression Language) syntax for keys.

The key must be a SpEL expression starting with # to access method parameters. Option B correctly uses #user.id.

🔧 Debug

advanced

Why does the cache not update after calling a @CachePut method?

Given this method:

  @CachePut(value = "products", key = "#product.id")
  public Product updateProduct(Product product) {
    productRepository.save(product);
    return product;
  }

Why might the cache not update after calling updateProduct?

A The method is called from within the same class, so Spring proxy does not intercept and update cache.

B The <code>productRepository.save(product)</code> does not update the database, so cache update is skipped.

C The method returns the same product instance without changes, so cache sees no update.

D The cache name 'products' is invalid and causes silent failure.

💡 Hint

Think about how Spring AOP proxies work with self-invocation.

Spring cache annotations work via proxies. If the method is called from the same class (self-invocation), the proxy is bypassed and caching annotations are not applied.

❓ state_output

advanced

What is the cache content after calling updateUser twice with different data?

Given this method:

  @CachePut(value = "users", key = "#user.id")
  public User updateUser(User user) {
    return user;
  }

And these calls:

  updateUser(new User(1, "Alice"));
  updateUser(new User(1, "Bob"));

What is the cached value for key 1?

A User object with id=1 and name='Bob'

B User object with id=1 and name='Alice'

C Cache is empty because @CachePut does not store values

D Cache contains both Alice and Bob objects under key 1

💡 Hint

Consider what happens when the same key is updated twice.

@CachePut updates the cache with the returned value each time. The second call overwrites the first cached value for key 1.

🧠 Conceptual

expert

Why use @CachePut instead of @Cacheable when updating data?

Which reason best explains why @CachePut is preferred over @Cacheable for methods that update data?

A @CachePut skips method execution if cache has the key, improving performance.

B @CachePut only caches null results to reduce cache size.

C @CachePut always executes the method and updates the cache, ensuring cache consistency after data changes.

D @CachePut clears the entire cache before method execution to avoid stale data.

💡 Hint

Think about cache consistency when data changes.

@CachePut ensures the method runs and the cache is updated with fresh data. @Cacheable may skip method execution and return stale cache data, which is not suitable for updates.