@Query for custom JPQL in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this JPQL query method?

Given the following Spring Data repository method using @Query, what will be the result when calling findActiveUsers() if the database has 3 users with active = true and 2 users with active = false?

Spring Boot

public interface UserRepository extends JpaRepository<User, Long> {
  @Query("SELECT u FROM User u WHERE u.active = true")
  List<User> findActiveUsers();
}

A A list containing 2 User objects with active = false

B A list containing all 5 User objects regardless of active status

C An empty list

D A list containing 3 User objects with active = true

💡 Hint

Look at the WHERE clause in the JPQL query.

The query selects users where the 'active' field is true, so only users with active = true are returned.

📝 Syntax

intermediate

Which @Query syntax is correct for selecting users by email?

You want to write a JPQL query to find a user by their email address. Which of the following @Query annotations is syntactically correct?

A @Query("SELECT u FROM User u WHERE u.email == :email")

B @Query("SELECT * FROM User WHERE email = :email")

C @Query("SELECT u FROM User u WHERE u.email = :email")

D @Query("SELECT u FROM User u WHERE u.email = ?1")

💡 Hint

JPQL uses entity names and fields, not table names or SQL syntax.

JPQL queries use entity names and fields, and parameters are referenced with a colon and name. '==' is invalid in JPQL, and '*' is not used.

🔧 Debug

advanced

What error does this @Query cause?

Consider this repository method:

 @Query("SELECT u FROM User u WHERE u.name = ?2")
User findByName(String name);

What error will occur when this method is called?

A org.springframework.dao.InvalidDataAccessApiUsageException due to parameter index out of bounds

B No error, method works correctly

C Syntax error in JPQL query

D NullPointerException at runtime

💡 Hint

Check the parameter index used in the query and method signature.

The query uses parameter index 2, but the method has only one parameter, so Spring throws an exception about invalid parameter index.

🧠 Conceptual

advanced

Which statement about @Query and JPQL is true?

Select the correct statement about using @Query with JPQL in Spring Data repositories.

A @Query cannot use parameters and must hardcode values.

B @Query allows defining JPQL queries that use entity names and fields, not table names.

C @Query queries must always use native SQL syntax.

D @Query queries are automatically converted to REST endpoints.

💡 Hint

Think about what JPQL queries look like compared to SQL.

JPQL queries use entity names and their fields, not database table names. @Query supports JPQL and native queries if specified.

❓ state_output

expert

What is the result of this @Query with JOIN and parameter?

Given these entities: User and Order, where User has a collection of Orders. Consider this repository method:

@Query("SELECT u FROM User u JOIN u.orders o WHERE o.status = :status")
List findUsersByOrderStatus(@Param("status") String status);

If the database has 2 users with orders of status 'SHIPPED' and 1 user with orders of status 'PENDING', what does calling findUsersByOrderStatus("SHIPPED") return?

A A list of 2 User objects who have at least one order with status 'SHIPPED'

B A list of all users regardless of order status

C A list of 1 User object with orders status 'PENDING'

D An empty list

💡 Hint

The query joins users with their orders and filters by order status.

The query returns users who have orders matching the given status. So users with 'SHIPPED' orders are returned.