Transaction Propagation example

Setup

• Jdk 1.8
• Maven 3.x
• H2

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Saving User then Message Entity From UserService to MessageService & check console logs to see transaction propagation

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1. Without Transaction Annotation In Both Method

- Both entity will be saved 

- curl --location 'localhost:8080/user/without-transaction'

2. Without Transaction Annotation In Both Method But Exception In MessageService

- `User` entity will save but `Message` will throw exception

- curl --location 'localhost:8080/user/without-transaction-exception'

3. Transaction Annotation In Both Method (Propagation REQUIRED) By Default

- Both entity will be saved 

- curl --location 'localhost:8080/user/transaction-required'

4. Transaction Annotation In Both Method (Propagation REQUIRED) By Default But Exception In MessageService

- If Exception occur in `MessageService` then rollback will happen, no data will save

- curl --location 'localhost:8080/user/transaction-required-exception'

5. Transaction -> UserServie (Propagation REQUIRED) & MessageService (Propagation REQUIRED_NEW)

- Both will save but `MessageService` will always create new transaction

- curl --location 'localhost:8080/user/transaction-required-new'

6. Transaction -> UserServie (Propagation REQUIRED) & MessageService (Propagation REQUIRED_NEW) With Exception

- `User Entity` will save but `MessageService` will always create new transaction and occur exception 
   then `UserService` has try catch block to handle `MessageService` method so that `User Entity` will save but `Message Entity` will not save
   if try catch is not there then it will rollback all entities

- curl --location 'localhost:8080/user/transaction-required-new-exception'

7. Transaction -> UserServie (Propagation REQUIRED) & MessageService (Propagation SUPPORT)

-  if it is directly called from `Controller` to `MessageService` then new transaction will be created

-  if it is called from `UserService` then same transaction will be used

- curl --location 'localhost:8080/user/transaction-support'

8. Transaction -> UserServie (Propagation REQUIRED) & MessageService (Propagation MANDATORY)

-  if it is directly called from `Controller` to `MessageService` then exception occur because there is no transaction

-  if it is called from `UserService` then same transaction will be used

- curl --location 'localhost:8080/user/transaction-mandatory'