@CachePut for updating cache in Spring Boot - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to use @CachePut to update the cache after method execution.

Spring Boot

@CachePut(value = "users", key = "#user.id")
public User [1](User user) {
    // update user logic
    return user;
}

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

AdeleteUser

BgetUser

CupdateUser

DcreateUser

Attempts:

3 left

💡 Hint

Common Mistakes

Using @CachePut on a method that only retrieves data without updating.

Choosing a method name that does not indicate updating.

The method annotated with @CachePut should update the cache, so the method name 'updateUser' fits the purpose.

2fill in blank

medium

Complete the code to specify the cache key using SpEL expression in @CachePut.

Spring Boot

@CachePut(value = "products", key = "[1]")
public Product updateProduct(Product product) {
    // update logic
    return product;
}

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

Aid

B#product.id

C#id

Dproduct.id

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting '#' in the SpEL expression.

Using a variable name not matching the method parameter.

The key expression in @CachePut uses SpEL and must reference the method parameter with #, so '#product.id' is correct.

3fill in blank

hard

Fix the error in the @CachePut annotation to correctly update the cache for the method.

Spring Boot

@CachePut(value = "orders", key = "[1]")
public Order updateOrder(Order order) {
    // update order logic
    return order;
}

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

A#orderId

Border.id

CorderId

D#order.id

Attempts:

3 left

💡 Hint

Common Mistakes

Using a key expression without '#' symbol.

Referencing a variable name not declared as a parameter.

The key must use SpEL with '#' and match the method parameter name, so '#order.id' is correct.

4fill in blank

hard

Fill both blanks to correctly use @CachePut with cache name and key expression.

Spring Boot

@CachePut(value = "[1]", key = "[2]")
public Customer updateCustomer(Customer customer) {
    return customer;
}

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

Acustomers

B#customer.id

C#id

Dusers

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong cache name that does not match the entity.

Incorrect key expression without '#' or wrong parameter name.

The cache name is 'customers' and the key expression must reference the method parameter with '#customer.id'.

5fill in blank

hard

Fill all three blanks to create a method that updates cache with @CachePut, specifying cache name, key, and method name.

Spring Boot

@CachePut(value = "[1]", key = "[2]")
public Product [3](Product product) {
    // update logic
    return product;
}

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

Aproducts

B#product.id

CupdateProduct

DsaveProduct

Attempts:

3 left

💡 Hint

Common Mistakes

Using inconsistent cache names.

Incorrect key expressions missing '#'.

Method names that do not reflect updating.

The cache name is 'products', the key expression is '#product.id', and the method name 'updateProduct' clearly indicates updating.

Practice

1. What is the primary purpose of the @CachePut annotation in Spring Boot?

easy

A. To update the cache with the method's return value after execution

B. To clear all entries in the cache before method execution

C. To cache the method result only if it is not already cached

D. To disable caching for the annotated method

Solution

1. Step 1: Understand the role of @CachePut

   @CachePut is used to update the cache with fresh data after the method runs, unlike @Cacheable which caches only if data is absent.

2. Step 2: Compare options with @CachePut behavior

   Only To update the cache with the method's return value after execution correctly describes updating the cache after method execution. Others describe different caching behaviors.

3. Final Answer:

   To update the cache with the method's return value after execution -> Option A

4. Quick Check:

   @CachePut updates cache after method runs [OK]

Hint: Remember: @CachePut always updates cache after method runs [OK]

Common Mistakes:

• Confusing @CachePut with @Cacheable
• Thinking @CachePut clears cache
• Assuming it caches only if absent

2. Which of the following is the correct syntax to use @CachePut to update a cache named "users" with a key based on the method parameter id?

easy

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

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

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

D. @CachePut(cache = "users", key = "#id")

Solution

1. Step 1: Recall correct attribute names for @CachePut

   The correct attribute for cache name is 'value' or 'cacheNames', and SpEL expressions for keys use '#'.

2. Step 2: Analyze each option's syntax

   @CachePut(value = "users", key = "#id") uses 'value' and '#id' correctly. Others use incorrect attribute names or miss the '#' for SpEL.

3. Final Answer:

   @CachePut(value = "users", key = "#id") -> Option B

4. Quick Check:

   Use 'value' and '#param' for key in @CachePut [OK]

Hint: Use 'value' for cache name and '#' before param in key [OK]

Common Mistakes:

• Using wrong attribute names like cacheName or cache
• Missing '#' in key expression
• Using plain string instead of SpEL for key

3. Given the following method in a Spring Boot service:

@CachePut(value = "products", key = "#product.id")
public Product updateProduct(Product product) {
    product.setPrice(product.getPrice() + 10);
    return product;
}

What will be the effect on the cache when this method is called with a product having id=5 and price=100?

medium

A. The cache is not affected because @CachePut only caches if absent

B. The cache entry with key 5 is removed from the cache

C. The cache entry with key 5 is updated with the product having price 110

D. A new cache entry with key 110 is added

Solution

1. Step 1: Understand @CachePut behavior on method call

   @CachePut updates the cache entry with the key specified after the method returns the updated object.

2. Step 2: Analyze the method logic and cache key

   The method increases price by 10 and returns the product. The key is product.id which is 5, so cache key 5 is updated with product price 110.

3. Final Answer:

   The cache entry with key 5 is updated with the product having price 110 -> Option C

4. Quick Check:

   @CachePut updates cache key with returned value [OK]

Hint: Returned value updates cache at key specified [OK]

Common Mistakes:

• Thinking cache key changes to price
• Assuming cache entry is removed
• Confusing @CachePut with @Cacheable

4. Consider this method annotated with @CachePut:

@CachePut(value = "orders", key = "#order.id")
public Order updateOrder(Order order) {
    // missing return statement
}

What is the problem with this code?

medium

A. The method should be annotated with @Cacheable instead

B. The key expression is invalid and causes a syntax error

C. The cache name 'orders' is not allowed in @CachePut

D. The method does not return a value, so cache cannot be updated

Solution

1. Step 1: Check method return requirement for @CachePut

   @CachePut requires the method to return a value to update the cache with that value.

2. Step 2: Identify missing return statement issue

   The method lacks a return statement, so no value is returned to update the cache, causing runtime issues.

3. Final Answer:

   The method does not return a value, so cache cannot be updated -> Option D

4. Quick Check:

   @CachePut needs method return to update cache [OK]

Hint: Always return updated value when using @CachePut [OK]

Common Mistakes:

• Forgetting to return the updated object
• Confusing cache name attribute
• Using @Cacheable instead of @CachePut incorrectly

5. You have a method that updates a user's email and you want to ensure the cache entry for that user is updated immediately after the change. Which approach correctly uses @CachePut to achieve this, assuming the method signature is public User updateEmail(Long userId, String newEmail)?

hard

A. @CachePut(value = "users", key = "#userId")
public User updateEmail(Long userId, String newEmail) {
User user = userRepository.findById(userId);
user.setEmail(newEmail);
userRepository.save(user);
return user;
}

B. @CachePut(value = "users", key = "#newEmail")
public User updateEmail(Long userId, String newEmail) {
User user = userRepository.findById(userId);
user.setEmail(newEmail);
userRepository.save(user);
return user;
}

C. @CachePut(value = "users")
public void updateEmail(Long userId, String newEmail) {
User user = userRepository.findById(userId);
user.setEmail(newEmail);
userRepository.save(user);
}

D. @CachePut(key = "#userId")
public User updateEmail(Long userId, String newEmail) {
User user = userRepository.findById(userId);
user.setEmail(newEmail);
userRepository.save(user);
return user;
}

Solution

1. Step 1: Verify correct cache name and key usage

   @CachePut(value = "users", key = "#userId") public User updateEmail(Long userId, String newEmail) { User user = userRepository.findById(userId); user.setEmail(newEmail); userRepository.save(user); return user; } uses 'value = "users"' and key '#userId', correctly identifying the cache and key.

2. Step 2: Check method return and update logic

   @CachePut(value = "users", key = "#userId") public User updateEmail(Long userId, String newEmail) { User user = userRepository.findById(userId); user.setEmail(newEmail); userRepository.save(user); return user; } returns the updated User object, which is necessary for @CachePut to update the cache. Other options either use wrong key, no return, or missing cache name.

3. Final Answer:

   @CachePut(value = "users", key = "#userId") public User updateEmail(Long userId, String newEmail) { User user = userRepository.findById(userId); user.setEmail(newEmail); userRepository.save(user); return user; } -> Option A

4. Quick Check:

   Return updated object and use correct cache name and key [OK]

Hint: Return updated object and use correct cache name and key [OK]

Common Mistakes:

• Using wrong key expression
• Not returning updated object
• Omitting cache name in annotation