Read-only transactions in Spring Boot - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What happens when a read-only transaction tries to perform a write?

Consider a Spring Boot service method annotated with @Transactional(readOnly = true). What is the expected behavior if this method attempts to save a new entity to the database?

Spring Boot

import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

@Service
public class UserService {

    @Transactional(readOnly = true)
    public void createUser(String name) {
        User user = new User();
        user.setName(name);
        userRepository.save(user); // Attempt to write inside read-only transaction
    }
}

A The save operation is ignored and no data is persisted, but no exception is thrown.

B The transaction commits successfully and the new user is saved to the database.

C The transaction silently rolls back without any exception or data change.

D An exception is thrown at runtime indicating that a write operation is not allowed in a read-only transaction.

💡 Hint

Think about how Spring enforces read-only transactions at runtime.

Spring marks the transaction as read-only, and depending on the database and transaction manager, attempting to write inside such a transaction typically causes an exception to prevent data modification.

📝 Syntax

intermediate

Identify the correct way to declare a read-only transaction in Spring Boot

Which of the following method annotations correctly configures a read-only transaction in Spring Boot?

A @Transactional(readonly = true)

B @Transactional(readOnly = true)

C @Transaction(readOnly = true)

D @Transactional(readOnly = "true")

💡 Hint

Pay attention to case sensitivity and annotation spelling.

The correct attribute name is 'readOnly' with capital 'O' and the annotation is '@Transactional'.

❓ state_output

advanced

What is the effect of read-only transactions on Hibernate's session flush?

In a Spring Boot application using Hibernate, what happens to the session flush behavior inside a method annotated with @Transactional(readOnly = true)?

A Hibernate throws an exception if any flush is attempted inside a read-only transaction.

B Hibernate flushes the session normally, committing all changes to the database.

C Hibernate disables automatic session flush, so changes are not synchronized with the database.

D Hibernate flushes only entity deletions but ignores inserts and updates.

💡 Hint

Think about how read-only transactions optimize performance by avoiding unnecessary writes.

In read-only transactions, Hibernate avoids flushing the session to prevent accidental data changes, improving performance.

🔧 Debug

advanced

Why does a read-only transaction still allow data modification in some cases?

A developer marks a service method with @Transactional(readOnly = true) but notices that data is still being updated in the database. What is the most likely cause?

A The underlying database or transaction manager does not enforce read-only transactions, so writes are allowed.

B The <code>readOnly</code> attribute was misspelled, so the annotation was ignored.

C The method is private, so Spring's transaction proxy does not apply the transaction.

D The entity manager is configured to ignore transaction settings.

💡 Hint

Consider how different databases handle read-only flags.

Some databases or transaction managers do not enforce read-only transactions, so writes can still occur despite the annotation.

🧠 Conceptual

expert

Why use read-only transactions in Spring Boot applications?

Which of the following is the best explanation for why developers use @Transactional(readOnly = true) in Spring Boot service methods?

A To optimize performance by avoiding unnecessary database locks and flushes during read operations.

B To automatically rollback any changes made during the transaction.

C To prevent any accidental data reads during write operations.

D To enable caching of all database queries within the transaction.

💡 Hint

Think about how read-only transactions affect database interaction and resource usage.

Read-only transactions help optimize performance by signaling the database and ORM to avoid unnecessary locking and flushing, improving efficiency for read operations.