JSTL Transaction Tag has Isolation attribute. It defines the level of isolation for this transaction. Value of this attribute can be TRANSACTION_READ_UNCOMMITTED, TRANSACTION_READ_COMMITTED, TRANSACTION_REPEATABLE_READ or TRANSACTION_SERIALIZABLE
1. TRANSACTION_READ_UNCOMMITTED: This allows dirty reads, non-repeatable reads, and phantom reads to occur.
2. TRANSACTION_READ_COMMITTED: This allows only commited data to read.
3. TRANSACTION_SERIALIZABLE: This does not allows dirty reads, non-repeatable reads, and phantom reads.
4. TRANSACTION_REPEATABLE_READ: This is close to transaction_serialazable except that it allows phantom reads.