Connection接口中定义了5中隔离级别常量
Connection.TRANSACTION_NONE -- 不支持事务
Connection.TRANSACTION_READ_UNCOMMITTED -- 脏读（事务回滚造成别的事务读取到的数据不准确），不可重复读和幻读均可发生
Connection.TRANSACTION_READ_COMMITTED -- 不可重复读和幻读均可发生
Connection.TRANSACTION_REPEATABLE_READ – 幻读发生（表一记录学生，表二记录表一统计信息。）
Connection.TRANSACTION_SERIALIZABLE -- 可串行化事务
Javax.ejb.TransactionAttributeType枚举中定义的事务属性：
TransactionAttributeType.MANDATORY
If a client invokes the enterprise bean's method while the client is associated with a transaction context, the container invokes the enterprise bean's method in the client's transaction context.
TransactionAttributeType.NEVER
The client is required to call without a transaction context, otherwise an exception is thrown.
TransactionAttributeType.NOT_SUPPORTED
The container invokes an enterprise bean method whose transaction attribute NOT_SUPPORTED with an unspecified transaction context.
TransactionAttributeType.REQUIRED
If a client invokes the enterprise bean's method while the client is associated with a transaction context, the container invokes the enterprise bean's method in the client's transaction context.
TransactionAttributeType.REQUIRES_NEW
The container must invoke an enterprise bean method whose transaction attribute is set to REQUIRES_NEW with a new transaction context.
TransactionAttributeType.SUPPORTS
If the client calls with a transaction context, the container performs the same steps as described in the REQUIRED case.