How do you define transaction propagation behavior in Spring?

Table of Contents

• Introduction
  • 1. Transaction Propagation Types in Spring
    • a. REQUIRED (default)
    • b. REQUIRES_NEW
    • c. MANDATORY
    • d. SUPPORTS
    • e. NOT_SUPPORTED
    • f. NEVER
    • g. NESTED
  • 2. When to Choose Which Propagation Type?
  • 3. Practical Example: Combining Propagation Types
• Conclusion

Introduction

Transaction propagation in Spring defines how transactions are handled when one transactional method calls another. The transaction propagation behavior is crucial when multiple service methods or operations need to be executed in a transaction. By controlling propagation, you can determine whether a method should join an existing transaction or whether a new one should be created.

In Spring, you can define transaction propagation behavior using the @Transactional annotation's propagation attribute. The Spring framework provides several types of propagation behaviors to handle different use cases, such as requiring new transactions, suspending the current transaction, or reusing an existing one.

This guide explains the different types of transaction propagation behavior in Spring and provides examples of how to configure them.

1. Transaction Propagation Types in Spring

Spring provides the following transaction propagation types that you can specify in the @Transactional annotation:

a. REQUIRED (default)

The REQUIRED propagation behavior is the default behavior in Spring. If there is an existing transaction, the current method will join that transaction. If no transaction exists, a new transaction will be created.

When to use it:
Use REQUIRED when you want methods to participate in an existing transaction if one exists, or start a new transaction if none exists. This is the most commonly used propagation type.

Example:

b. REQUIRES_NEW

The REQUIRES_NEW propagation behavior creates a new transaction, suspending any existing transaction. The current transaction, if any, is paused until the new transaction completes.

When to use it:
Use REQUIRES_NEW when you want to ensure that a method always runs in a new transaction, even if an existing transaction is in progress. This is useful in scenarios where certain actions (e.g., logging, sending notifications) need to occur independently of the main transaction.

Example:

In this example, the processPayment method will always execute within its own transaction, regardless of whether there is an existing transaction in progress.

c. MANDATORY

The MANDATORY propagation type requires that a transaction already exists. If there is no active transaction when the method is invoked, Spring will throw an exception.

When to use it:
Use MANDATORY when you want to ensure that the method is always called within an existing transaction. This is useful when you want to enforce that certain methods only run when a surrounding transaction is active.

Example:

If there is no active transaction, Spring will throw an exception.

d. SUPPORTS

The SUPPORTS propagation type indicates that the method can run within an existing transaction if one exists, but it will not require a transaction. If no transaction is present, the method will execute without one.

When to use it:
Use SUPPORTS when you don't require a transaction, but if one exists, you want to participate in it. This is useful for read-only operations or when a transaction is optional.

Example:

If a transaction exists, the method will participate in it; otherwise, it will run without one.

e. NOT_SUPPORTED

The NOT_SUPPORTED propagation type suspends any existing transaction and ensures that the method does not run within a transaction. The transaction, if any, is paused for the duration of the method.

When to use it:
Use NOT_SUPPORTED when you need to ensure that a method does not participate in a transaction, even if one exists. This is useful for operations that should not be executed within a transaction (e.g., certain logging or auditing operations).

Example:

f. NEVER

The NEVER propagation type ensures that the method does not run within a transaction. If there is an existing transaction, it will throw an exception.

When to use it:
Use NEVER when the method should never execute within a transaction, and you want to ensure that there is no active transaction when the method is invoked.

Example:

If there is an active transaction, Spring will throw an exception, indicating that the method should not be executed within a transaction.

g. NESTED

The NESTED propagation type creates a nested transaction if there is an existing transaction. A nested transaction is effectively a sub-transaction of the parent, meaning that if the nested transaction fails, only the nested changes are rolled back, while the parent transaction can continue to commit.

When to use it:
Use NESTED when you want to execute a method within a transaction but still retain the ability to roll back the method’s changes independently of the parent transaction.

Example:

2. When to Choose Which Propagation Type?

• REQUIRED: Default option. Suitable for most cases where the method should participate in an existing transaction or start a new one if none exists.
• REQUIRES_NEW: Use when the method must always run in its own transaction, regardless of any existing transaction.
• MANDATORY: Use when the method should only run if there is an existing transaction.
• SUPPORTS: Use when the method can run without a transaction but should participate in one if available.
• NOT_SUPPORTED: Use when the method should not run within a transaction, even if one exists.
• NEVER: Use when the method should never run with a transaction, and an exception should be thrown if one exists.
• NESTED: Use when you need a nested transaction that can be committed or rolled back independently of the parent transaction.

3. Practical Example: Combining Propagation Types

Consider an e-commerce system with order processing, inventory updating, and payment processing. You might want to ensure that:

1. Inventory updates are always part of the same transaction as the order creation (REQUIRED).
2. Payment processing always occurs in a new, independent transaction (REQUIRES_NEW).
3. Auditing (logging) actions should not participate in transactions (NOT_SUPPORTED).

Conclusion

Understanding and configuring transaction propagation behavior in Spring is essential for building robust and flexible applications. The @Transactional annotation provides several propagation options, each suited to different use cases, such as joining existing transactions, creating new ones, or suspending transactions temporarily. By selecting the right propagation type, you can control how Spring manages transaction boundaries in your application, ensuring data consistency and optimal performance.