What are the different levels of transaction isolation in Spring?

In Spring, transaction isolation levels are defined through the TransactionDefinition interface, which includes the following five isolation levels:

1. DEFAULT: Utilize the default isolation level of the underlying database.
2. READ_UNCOMMITTED: Allows transactions to read uncommitted data, potentially leading to issues such as dirty reads, phantom reads, and non-repeatable reads.
3. READ_COMMITTED: Transactions can only read data that has already been committed. This can resolve the issue of dirty reads, but may still result in phantom reads and non-repeatable reads.
4. REPEATABLE_READ: Allows for multiple reads of the same data within a transaction, ensuring that the results obtained are consistent each time. This can address issues of dirty reads and non-repeatable reads, but may still encounter problems with phantom reads.
5. SERIALIZABLE: The highest level of isolation where transactions are executed one after the other, effectively addressing issues such as dirty reads, phantom reads, and non-repeatable reads, but with lower performance.

One option for setting the isolation level of a transaction is by specifying the isolation attribute in the @Transactional annotation. For example:

@Transactional with isolation level of READ_COMMITTED is used to perform some transactional operations within the method doSomething().