What is Transaction Management

The sequence of activities that will be performed to complete database operation and its management is known as Transaction Management. All these actions in combination will be treated as ONE action only. So that DB doesn’t fall in inconsistent mode ever. For more details, you can search for ACID property of relation DB.

Type of Transaction Management

In J2EE, Transaction Management can be divided into two types.

1. Global Transaction
2. Local Transaction

Global Transaction

• Use to work with multiple transaction resources like RDBMS or Message Queue (Pros)
• Managed by Application Server (WebSphere, Weblogic) using JTA (Cons)
• JNDI is required to use JTA
• Code can not be reused as JTA is available at server level(Cons)
• Example of Global Transaction : EJB CMT

Local Transaction

• Use to work with specific resource(transaction associated with JDBC)
• Can not work across multiple transaction resource opposite to Global transaction (cons)
• Most of web application uses only single resources hence it is best option to use in normal app.

Spring Framework Transaction Management

As you can see above there are some pros and cons associated with both approaches. Spring transaction management tries to resolve the problem of both transactions. A consistent programming model approach can be used in any environment. The same code will work for different transactions management in different environments.

Different Approach for transaction management

Spring supports two different approaches to transaction management.

Programmatic Transaction Management

Here you will write code for transaction management. Spring API dependency. Not good for maintenance. Good for development. Flexibility.

Declarative Transaction Management

Here you will use XML or annotation for transaction management. Less flexible but preferable over programmatic approach. In normal cases, no code is required for transaction management.

Spring transaction management abstraction

To understand transaction management you should understand abstraction(Transaction strategy) in Spring. Which is defined in Spring using PlatformTransactionManager Interface.

public interface PlatformTransactionManager {

  TransactionStatus getTransaction(TransactionDefinition definition)
    throws TransactionException;

  void commit(TransactionStatus status) throws TransactionException;

  void rollback(TransactionStatus status) throws TransactionException;
}

As you can see in PlatformTransactionManager Interface all methods throw TransactionException. This Exception itself is UncheckedException means the developer is not forced to handle these exceptions. 

TransactionDefinition

TransactionDefinition is an Interface that specifies below 4 points.

1. Isolation
2. Propagation
3. Timeout
4. Read-Only status

Isolation

The degree to which a particular transaction is isolated from other Transactions. Below is the list of Isolation levels and their details

DEFAULT	Default isolation level. It uses the isolation of the underlying data source.
READ_COMMITTED	Dirty reads NOT supported; Non-repeatable reads and Phantom reads can occur.
READ_UNCOMMITTED	Dirty reads / Non-repeatable reads / Phantom reads all can occur.
REPEATABLE_READ	Dirty reads and non-repeatable reads are prevented; phantom reads can occur.
SERIALIZABLE	Dirty reads, non-repeatable reads and phantom reads are prevented.

Propagation

MANDATORY	Support a current transaction
NESTED	Execute within a nested transaction if a current transaction exists
NEVER	Execute non-transactionally
NOT_SUPPORTED	Execute non-transactionally
REQUIRED	Support a current transaction
REQUIRES_NEW	Create a new transaction, suspend the current transaction if one exists.
SUPPORTS	Support a current transaction, execute non-transaction if none exists.

Timeout

This setting is used to define how long this transaction may run before timing out (candidate for rolled back by the underlying transaction infrastructure).

Read-Only Status

This setting is used to specify a read-only transaction. As read-only transactions do not modify any data. Hence it is optimized in some cases.