What is the significance of the @Transactional(propagation = Propagation.REQUIRES_NEW) annotation?

Table of Contents

Introduction

The @Transactional annotation in Spring provides declarative transaction management, which simplifies working with databases by automatically handling transactions. One of the most important aspects of transaction management is transaction propagation, which defines how transactions interact with each other. The **@Transactional(propagation = Propagation.REQUIRES_NEW)** annotation plays a key role in scenarios where a new transaction must be created, even if there is an existing one.

In this article, we'll explore the **REQUIRES_NEW** propagation level, its significance, and how to use it effectively in Spring applications.

What is the @Transactional(propagation = Propagation.REQUIRES_NEW)?

The **REQUIRES_NEW** propagation type instructs Spring to suspend any existing transaction (if there is one) and create a new transaction. This means that when a method annotated with @Transactional(propagation = Propagation.REQUIRES_NEW) is called, it will always run in its own independent transaction, regardless of whether the caller method is already in a transaction.

Transaction Propagation Types

In Spring, the **@Transactional** annotation supports several propagation types that control how transactions interact. Here is a quick summary of the most common ones:

  • **REQUIRES_NEW**: Suspends the current transaction (if any) and creates a new one.
  • **REQUIRED** (default): Joins the current transaction if one exists, or creates a new one if none exists.
  • **NESTED**: Creates a nested transaction, which is part of the current transaction but can be rolled back independently.
  • **SUPPORTS**: Participates in the current transaction if one exists, otherwise executes without a transaction.
  • **MANDATORY**: Requires an existing transaction; throws an exception if no transaction exists.
  • **NEVER**: Executes without a transaction; throws an exception if a transaction exists.

When to Use REQUIRES_NEW?

The **REQUIRES_NEW** propagation level is useful in scenarios where you want to ensure that a certain method runs in a separate transaction, regardless of the caller's transaction. This can be important in the following cases:

  1. Independent Sub-Transactions: When a part of your code needs to be independent of the existing transaction, and it must commit or rollback separately. For example, when logging or auditing actions need to be handled in their own transaction.
  2. Ensuring Transactional Integrity: If a method must succeed or fail on its own, regardless of the state of the calling method’s transaction, REQUIRES_NEW ensures that it always has a dedicated transaction.
  3. Nested Transactions: While the **NESTED** propagation can be used for nested transactions, **REQUIRES_NEW** creates a completely separate transaction and is suitable when the calling transaction should not affect the outcome of the current one.

Example: Using @Transactional(propagation = Propagation.REQUIRES_NEW)

Let’s walk through an example to see how **REQUIRES_NEW** behaves.

Scenario

Imagine a service where we are saving user information in a primary table (User) and logging that action in an audit table (Audit). We want the logging action to always succeed, even if the user data save fails (and vice versa).

Step 1: Service Layer

Step 2: AuditService with REQUIRES_NEW

Explanation:

  • **UserService** has a main business method that saves a user and logs an action. The logAction() method is annotated with @Transactional(propagation = Propagation.REQUIRES_NEW), meaning it will always run in a separate transaction.
  • If an exception occurs while saving the User, the audit log will still be created in its own independent transaction, because logAction() runs with REQUIRES_NEW.

Step 3: Behavior

Let’s break down what happens when we call createUser():

  1. Transaction 1 (UserService): A transaction is started for saving the user.
  2. Transaction 2 (AuditService): When the logAction() method is called, a new transaction is started, suspending the user transaction.
  3. The user save operation will commit or rollback independently of the audit log operation.

Handling Errors

In case the user save fails (e.g., due to a database constraint violation), the audit log will still be created in its own transaction. This ensures that logging actions are always performed, even if the main operation fails.

Conclusion

The **@Transactional(propagation = Propagation.REQUIRES_NEW)** annotation is a powerful tool in Spring transaction management that allows you to suspend an existing transaction and create a new, independent transaction. This is useful in scenarios where operations need to be isolated, such as logging, auditing, or when certain business logic must not be affected by the surrounding transaction.

Key Points:

  • **REQUIRES_NEW** creates a new transaction and suspends any existing one.
  • It ensures that specific operations run in their own independent transaction, unaffected by others.
  • Common use cases include logging, auditing, and ensuring transactional integrity for certain parts of the code.

Using this propagation type carefully can help ensure that your business logic is resilient and transactions are managed efficiently, providing the desired isolation and consistency for critical operations.

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