f597fc1b07
* Fix languages * Missed change for version number * Add language field for presentation * Revert change in README for double buffer Co-authored-by: Jackie Nim <=>
121 lines
3.6 KiB
Markdown
121 lines
3.6 KiB
Markdown
---
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layout: pattern
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title: Transaction Script
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folder: transaction-script
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permalink: /patterns/transaction-script/
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categories: Behavioral
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language: en
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tags:
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- Data access
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---
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## Intent
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Transaction Script organizes business logic by procedures where each procedure handles a single
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request from the presentation.
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## Explanation
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Real world example
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> You need to create a hotel room booking system. Since the requirements are quite simple we intend
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> to use the Transaction Script pattern here.
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In plain words
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> Transaction Script organizes business logic into transactions that the system needs to carry out.
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Programmatic example
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The `Hotel` class takes care of booking and cancelling room reservations.
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```java
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@Slf4j
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public class Hotel {
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private final HotelDaoImpl hotelDao;
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public Hotel(HotelDaoImpl hotelDao) {
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this.hotelDao = hotelDao;
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}
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public void bookRoom(int roomNumber) throws Exception {
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Optional<Room> room = hotelDao.getById(roomNumber);
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if (room.isEmpty()) {
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throw new Exception("Room number: " + roomNumber + " does not exist");
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} else {
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if (room.get().isBooked()) {
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throw new Exception("Room already booked!");
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} else {
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Room updateRoomBooking = room.get();
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updateRoomBooking.setBooked(true);
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hotelDao.update(updateRoomBooking);
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}
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}
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}
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public void cancelRoomBooking(int roomNumber) throws Exception {
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Optional<Room> room = hotelDao.getById(roomNumber);
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if (room.isEmpty()) {
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throw new Exception("Room number: " + roomNumber + " does not exist");
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} else {
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if (room.get().isBooked()) {
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Room updateRoomBooking = room.get();
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updateRoomBooking.setBooked(false);
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int refundAmount = updateRoomBooking.getPrice();
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hotelDao.update(updateRoomBooking);
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LOGGER.info("Booking cancelled for room number: " + roomNumber);
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LOGGER.info(refundAmount + " is refunded");
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} else {
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throw new Exception("No booking for the room exists");
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}
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}
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}
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}
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```
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The `Hotel` class has two methods, one for booking and cancelling a room respectively. Each one of
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them handles a single transaction in the system, making `Hotel` implement the Transaction Script
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pattern.
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The `bookRoom` method consolidates all the needed steps like checking if the room is already booked
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or not, if not booked then books the room and updates the database by using the DAO.
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The `cancelRoom` method consolidates steps like checking if the room is booked or not,
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if booked then calculates the refund amount and updates the database using the DAO.
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## Class diagram
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## Applicability
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Use the Transaction Script pattern when the application has only a small amount of logic and that
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logic won't be extended in the future.
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## Consequences
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* As the business logic gets more complicated,
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it gets progressively harder to keep the transaction script
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in a well-designed state.
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* Code duplication between transaction scripts can occur.
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* Normally not easy to refactor transactions script to other domain logic
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patterns.
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## Related patterns
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* Domain Model
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* Table Module
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* Service Layer
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## Credits
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* [Transaction Script Pattern](https://dzone.com/articles/transaction-script-pattern#:~:text=Transaction%20Script%20(TS)%20is%20the,need%20big%20architecture%20behind%20them.)
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* [Transaction Script](https://www.informit.com/articles/article.aspx?p=1398617)
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* [Patterns of Enterprise Application Architecture](https://www.amazon.com/gp/product/0321127420/ref=as_li_qf_asin_il_tl?ie=UTF8&tag=javadesignpat-20&creative=9325&linkCode=as2&creativeASIN=0321127420&linkId=18acc13ba60d66690009505577c45c04)
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