Read-only transactions in Spring Boot

Introduction

Read-only transactions tell the system you only want to look at data, not change it. This helps the system work faster and safer.

When fetching data to show on a webpage without changing it.

When running reports that only read data.

When checking if some data exists without updating it.

When calling a service method that only reads from the database.

When you want to avoid accidental data changes during a process.

Syntax

Spring Boot

@Transactional(readOnly = true)
public ReturnType methodName() {
    // code that only reads data
}

Use @Transactional(readOnly = true) on methods that only read data.

This hint can improve performance and avoid accidental writes.

Examples

This method fetches all users without changing anything.

Spring Boot

@Transactional(readOnly = true)
public List<User> getAllUsers() {
    return userRepository.findAll();
}

This method looks up a product by its ID safely without modifying data.

Spring Boot

@Transactional(readOnly = true)
public Optional<Product> findProductById(Long id) {
    return productRepository.findById(id);
}

Sample Program

This service class has a method to get all books. The method is marked as read-only transaction because it only reads data.

Spring Boot

import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;
import java.util.List;

@Service
public class BookService {

    private final BookRepository bookRepository;

    public BookService(BookRepository bookRepository) {
        this.bookRepository = bookRepository;
    }

    @Transactional(readOnly = true)
    public List<Book> getAllBooks() {
        return bookRepository.findAll();
    }
}

// Assume BookRepository extends JpaRepository<Book, Long>

Important Notes

Read-only transactions can help databases optimize queries.

Do not try to save or update data inside a read-only transaction; it may cause errors or be ignored.

Summary

Use read-only transactions when you only need to read data.

Mark methods with @Transactional(readOnly = true) in Spring Boot.

This improves performance and prevents accidental data changes.