Custom query methods by naming convention in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What does this Spring Data JPA method return?

Given the method List findByAgeGreaterThan(int age); in a repository interface, what will it return when called with findByAgeGreaterThan(30)?

A All users with age less than 30

B All users with age exactly 30

C All users with age greater than 30

D All users with age greater than or equal to 30

💡 Hint

Think about the meaning of 'GreaterThan' in the method name.

The method name 'findByAgeGreaterThan' tells Spring Data JPA to find all users whose age is strictly greater than the given value.

📝 Syntax

intermediate

Which method signature is valid for finding users by last name and active status?

You want to create a method in a Spring Data JPA repository to find users by their last name and whether they are active. Which method signature is valid?

A List<User> findByLastName_And_Active(String lastName, boolean active);

B List<User> findByLastNameAndActive(String lastName, boolean active);

C List<User> findByLastNameActive(String lastName, boolean active);

D List<User> findByLastNameOrActive(String lastName, boolean active);

💡 Hint

Use 'And' to combine conditions in method names.

Spring Data JPA supports 'And' and 'Or' keywords to combine conditions. The method name must follow camel case with these keywords.

🔧 Debug

advanced

Why does this method cause a runtime error?

Consider this method in a Spring Data JPA repository:
List findByEmailContainingIgnoreCaseOrderByAgeDesc(String emailPart);
At runtime, calling this method causes an error. What is the most likely cause?

A The method name is valid but the entity does not have an 'age' field

B The method name is too long and exceeds Spring Data limits

C The method name uses unsupported keywords 'ContainingIgnoreCase' and 'OrderBy' together

D The method should return a single User, not a list

💡 Hint

Check if all fields in the method name exist in the entity.

If the entity lacks the 'age' field, Spring Data cannot create the query and throws an error at runtime.

🧠 Conceptual

advanced

What is the effect of using 'Distinct' in method names?

In Spring Data JPA, what does adding 'Distinct' to a query method name do?
For example: List findDistinctByCity(String city);

A It removes duplicate users from the result list

B It filters users with distinct cities

C It sorts the users by city

D It returns only one user from the city

💡 Hint

Think about what 'distinct' means in database queries.

'Distinct' ensures the query returns unique results without duplicates.

❓ state_output

expert

What is the size of the result list after calling this method?

Given a User entity with fields id, name, age and a repository method:
List findByAgeBetween(int start, int end);
Assume the database has users with ages: 20, 25, 30, 35, 40.
What is the size of the list returned by findByAgeBetween(25, 35)?

A 2

B 5

C 4

D 3

💡 Hint

The 'Between' keyword includes both start and end values.

Ages 25, 30, and 35 are included, so the list size is 3.