Spring Framework

Spring Life Cycle:

BeanFacory vs ApplicationContext:

Annotation	Purpose	Scope
@Autowired	Auto-wires dependencies by type	Constructor, Field, Setter
@Qualifier	Specifies which bean to inject	With @Autowired
@Primary	Sets default bean when multiple candidates exist	On bean definitions
@Bean	Declares a bean in a config class	@Configuration classes
@Value	Injects property values or expressions	Fields
@Profile	Activates beans for specific environments	On components/config classes
@Configuration	Declares a configuration class	Application setup
@ComponentScan	Scans for Spring components	Main class or config classes
@Scope	Defines bean lifecycle (singleton, prototype)	On beans
@PostConstruct	Initializes beans after dependency injection	Bean lifecycle
@PreDestroy	Cleans up before bean destruction	Bean lifecycle

@Order

Approach	Pros	Cons
ObjectFactory<T>	Simple, lightweight	Some boilerplate code
Provider<T>	Better readability, cleaner	Requires jakarta.inject
@Lookup Method Injection	No need for Provider	Less flexible, needs subclassing

TransactionManagement:
Spring Transaction Abstraction:

The key to the Spring transaction abstraction is defined by the org.springframework.transaction.PlatformTransactionManager interface, which is as follows −

public interface PlatformTransactionManager {
   TransactionStatus getTransaction(TransactionDefinition definition);
   throws TransactionException;
   
   void commit(TransactionStatus status) throws TransactionException;
   void rollback(TransactionStatus status) throws TransactionException;
}

The TransactionDefinition is the core interface of the transaction support in Spring and it is defined as follows −

public interface TransactionDefinition {
   int getPropagationBehavior();
   int getIsolationLevel();
   String getName();
   int getTimeout();
   boolean isReadOnly();
}

Isolation:

TransactionDefinition.ISOLATION_DEFAULT
This is the default isolation level.

TransactionDefinition.ISOLATION_READ_UNCOMMITTED

Indicates that dirty reads, non-repeatable reads, and phantom reads can occur.

TransactionDefinition.ISOLATION_READ_COMMITTED

Indicates that dirty reads are prevented; non-repeatable reads and phantom reads can occur.

TransactionDefinition.ISOLATION_REPEATABLE_READ

Indicates that dirty reads and non-repeatable reads are prevented; phantom reads can occur.
TransactionDefinition.ISOLATION_SERIALIZABLE

Indicates that dirty reads, non-repeatable reads, and phantom reads are prevented.

Propagation:

TransactionDefinition.PROPAGATION_REQUIRED

Supports a current transaction; creates a new one if none exists.
TransactionDefinition.PROPAGATION_REQUIRES_NEW
Creates a new transaction, suspending the current transaction if one exists.
TransactionDefinition.PROPAGATION_MANDATORY
Supports a current transaction; throws an exception if no current transaction exists.
TransactionDefinition.PROPAGATION_NESTED
Executes within a nested transaction if a current transaction exists.
TransactionDefinition.PROPAGATION_NEVER
Does not support a current transaction; throws an exception if a current transaction exists.
TransactionDefinition.PROPAGATION_SUPPORTS
Supports a current transaction; executes non-transactionally if
TransactionDefinition.PROPAGATION_NOT_SUPPORTED
Does not support a current transaction; rather always execute nontransactionally.
TransactionDefinition.TIMEOUT_DEFAULT
Uses the default timeout of the underlying transaction system, or none if timeouts are not supported.

TransactionStatus:

public interface TransactionStatus extends SavepointManager {
   boolean isNewTransaction();
   boolean hasSavepoint();
   void setRollbackOnly();
   boolean isRollbackOnly();
   boolean isCompleted();
}