Spring Transaction Management

 

• Transaction Propagation : Propagation defines our business logic's transaction boundary. Spring manages to start and pause a transaction according to our propagation setting. (in other words  : Defines how transactions relate to each other)
• REQUIRED : Code will always run in a transaction. Creates a new transaction or reuses one if available.
• REQUIRED_NEW : Code will always run in a new transaction. Suspends the current transaction if one exists.
• SUPPORTS
• MANDATORY
• NEVER
• NOT_SUPPORTED
• NESTED
  
  
• Transaction  Isolation :  solation is one of the common ACID properties: Atomicity, Consistency, Isolation, and Durability. Isolation describes how changes applied by concurrent transactions are visible to each other. (in other words :  Defines the data contract between transactions)
  Isolation Levels
• DEFAULT 
• READ_UNCOMMITTED : Allows dirty reads
• READ_COMMITTED :  Does not allow dirty reads
• REPEATABLE_READ : If a row is read twice in the same transaction, the result will always be the same 
• SERIALIZABLE : Performs all transactions in a sequence

Each isolation level prevents zero or more concurrency side effects on a transaction:

Dirty read: read the uncommitted change of a concurrent transaction

Nonrepeatable read: get different value on re-read of a row if a concurrent transaction updates the same row and commits

Phantom read: get different rows after re-execution of a range query if another transaction adds or removes some rows in the range and commits

References

Baeldung : link 

Stackoverflow : link

Transactions with Spring and JPA : link