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  • https://www.baeldung.com/transaction-configuration-with-jpa-and-spring - topics

Hibernate - Transaction management

  • add @Bean PlatformTransactionManager
  • add @EnableTransactionManagement, or add spring-data-*-starter dependencies
  • org.springframework.transaction = DEBUG
  • fact:
  • Mixing the database I/O with other types of I/O in a transactional context isn’t a great idea.

A. @Transactional

  • manage transaction boundaries in a declarative way.
  • Spring creates proxies, to inject transactional-logic, before and after the running method.
  • only public methods.
  • best place apply on service method
  • can also apply on repo methods
  • @Transactional(attribtes=) : check below

propagation

  • purpose:
  • define the transactional behavior between multiple transactional methods.
  • how the transaction management system handles existing and new transactions
  • requires_new -> AlwaysNewT
  • If a transaction exists, the current method will join it
  • If no transaction exists, a new one will be created.
  • Required -> t1 else t2new
  • Suspends any existing transaction and starts a new one
  • mandatory -> t1 else ex
  • Requires an existing transaction

  • If no transaction exists, an exception is thrown

  • SUPPORTS -> t1

  • If a transaction exists, the method will participate in it.
  • If no transaction exists, it will execute non-transactionally
  • none / NOT_SUPPORTED
  • Suspends any existing transaction and executes non-transactionally.
  • never ->
  • Must execute without a transaction
  • Throws an exception if a transaction exists
  • Nested
  • inner txn : independent transaction within the context of an existing/outer transaction.
  • if inner transaction rolls back, it only rolls back the nested transaction, not the outer transaction.
  • Not all databases and transaction managers provide full support for nested transactions.
  • it uses Save points.
  • enable it: 
      @Bean
  public PlatformTransactionManager transactionManager(DataSource dataSource) 
  {
    DataSourceTransactionManager transactionManager = new DataSourceTransactionManager(dataSource);
    transactionManager.setNestedTransactionAllowed(true); // Enable nested transactions                   <<< 
    return transactionManager;
  }

isolation

  • txn side effect : Dirty-read, Non-repeatable read, Phantom read.
  • protection levele: READ_UNCOMMITTED, READ_COMMITTED, REPEATABLE_READ and SERIALIZABLE.
  • can check: 03_ACID.md

timeout

readOnly

– t/f - just a hint for the persistence provider that the transaction should be read only. - optimizes performance.

rollbackFor / noRollbackFor

  • @Transactional(rollbackFor = {Exception.class, SpecificException.class})
  • @Transactional(rollbackForClassName = {"java.lang.Exception", "com.example.SpecificException"})
  • if we don't mention any rule, rollback happens on unchecked-exceptions/RuntimeException

B. programmatic txn

intro

  • check StudentServiceImpl.java
  • TransactionTemplate utility provided by Spring to programmatically manage transaction
  • Amix with AOP
  • open and search : https://chatgpt.com/c/7b6dd03e-ca98-44d5-87a6-73c23026a009