T- the value type of the resource. For instance, @see java.lang.Float for
public interface TransactionFuture<T>
getValue()method returns the resource value read in a transaction. If getValue() is called before the transaction has been executed, an exception is thrown.
T getValue() throws java.lang.IllegalStateException
java.lang.IllegalStateException- If the associated transaction has not been executed yet, or any of the operations involved in the transaction has thrown an exception, hence causing a rollback.