Optimal isolation levels

As we learned in the previous section, the concept of a transaction is described with ACID. Transaction isolation level is a concept that is not limited to Spring Framework but is applicable to any application that interacts with a database. The isolation level defines how the changes made to some data repository by one transaction affect other concurrent transactions, and also how and when that changed data becomes available to other transactions. In Spring Framework, we define the isolation level of a transaction along with the @Transaction annotation.

The following snippet is an example of how we can define the isolation level in a transactional method:

@Autowired
private AccountDao accountDao;

@Transactional(isolation=Isolation.READ_UNCOMMITTED)
public void someTransactionalMethod(User user) {

  // Interact with accountDao

} 

In the preceding code, we defined a method with a transaction isolation level of READ_UNCOMMITTED. This means that the transaction in this...