Mastering Spring Transaction Propagation: When and How Transactions Flow

1. What Is Spring Transaction Propagation?

In a Spring application, transaction propagation defines how transactions are handled when a transactional method calls another transactional method. It determines whether the called method joins the existing transaction, starts a new one, or executes without a transaction.

2. The Seven Propagation Types

PROPAGATION_REQUIRED : Join the current transaction if one exists; otherwise start a new transaction.

PROPAGATION_SUPPORTS : Execute within the current transaction if present; otherwise run non‑transactionally.

PROPAGATION_MANDATORY : Must run inside a transaction; throws an exception if none exists.

PROPAGATION_REQUIRES_NEW : Always start a new transaction, suspending any existing one.

PROPAGATION_NOT_SUPPORTED : Suspend any existing transaction and run non‑transactionally.

PROPAGATION_NEVER : Throw an exception if a transaction is present; otherwise run non‑transactionally.

PROPAGATION_NESTED : Execute within a nested transaction (savepoint) if a transaction exists; otherwise behaves like REQUIRED.

3. How Each Propagation Works

3.1 REQUIRED

The default mode. All nested transactional methods share the same transaction, so they commit or roll back together.

Example: Method A (REQUIRED) calls Method B (REQUIRED). Both operations are performed in a single transaction; if B throws an exception, the whole transaction rolls back.

3.2 REQUIRES_NEW

A new, independent transaction is started for the called method, suspending the outer transaction.

When Method A (REQUIRED) invokes Method B (REQUIRES_NEW), A's transaction is paused, B runs in its own transaction, and after B commits, A's transaction resumes.

3.3 SUPPORTS

If a transaction exists, the method joins it; otherwise it runs non‑transactionally.

Example 1: Neither A nor B has @Transactional; B (SUPPORTS) runs without a transaction. Example 2: A (REQUIRED) starts a transaction, B (SUPPORTS) joins it.

3.4 NOT_SUPPORTED

The method always runs non‑transactionally, suspending any existing transaction.

Example: A (REQUIRED) starts a transaction, B (NOT_SUPPORTED) suspends it, runs non‑transactionally, then A's transaction resumes and commits.

3.5 NEVER

The method must not run inside a transaction; an exception is thrown if a transaction is present.

When A (REQUIRED) calls B (NEVER), B throws an exception, causing A's transaction to roll back.

3.6 MANDATORY

The method must run inside an existing transaction; otherwise an exception is thrown.

If A has no transaction, B (MANDATORY) throws an exception. If A already has a transaction, B joins it.

3.7 NESTED

Creates a savepoint within the existing transaction, allowing the inner transaction to roll back independently.

Example: A (REQUIRED) starts a transaction, B (NESTED) creates a savepoint. If B fails, only B's changes roll back to the savepoint while A can still commit.

4. Summary

The article clarifies how Spring handles transaction propagation across multiple service methods. Understanding the seven propagation levels—REQUIRED, SUPPORTS, MANDATORY, REQUIRES_NEW, NOT_SUPPORTED, NEVER, and NESTED—helps developers choose the appropriate strategy for their business scenarios, ensuring correct commit and rollback behavior in enterprise applications.