Implemented in the Java Backend Developer Track of hyperskill.org JetBrain Academy.
Main purpose of doing this project, is to complete the Java Backend Developer track, which now is at 93% applied core topics and 98% learned topics overall.
But above all, the project sounds fun and challenging from comments. It is in an early beta version, has few completions, so it seems like a challenge and opportunity to deepen the Spring boot experiences - though I am working with Spring boot professionally every day now.
- Spring Boot 3.0.2,
- Spring Command Line Runner
- H2 Database 2.1.214 or later
- Spring Data JPA / Hibernate / JPA data projection
- Lombok's annotation processors,
- Apache Log4j SLF4J API binding to Log4j 2 logging and
- Junit 5 with
- Mockito (mockito-inline) testing.
The sources of main project tasks (6 stages) and the unit, mockito, spring testing.
Commands presently supported:
[date] borrow PersonOne PersonTwo amount
PersonTwo lent some amount to PersonOne on the specified date
[date] repay PersonOne PersonTwo amount
PersonOne repaid an amount to PersonTwo on the date.
[date] balance [open|close] \[(+/- list of names and groups)\]
Calculate and display the list of repayments with names and amounts to be repaid in the natural sorted order for the balance date. Here open refers to the opening balance on the first day of the month and close refers to the closing balance on that specific date. The list of names and groups is resolved and the balance filters (i.e. displays only) those owers who are amongst the resolved names
[date] balancePerfect [open|close] \[(+/- list of names and groups)\]
Calculate and display the list of repayments as in the balance command above, but do an optimization of repayments, e.g. net owing sums in a way, that as few transactions, repayments as possible are needed to resettle all debts. (cf: https://stackoverflow.com/questions/1163116/algorithm-to-determine-minimum-payments-amongst-a-group)
group create|show|add|remove GROUPNAME [(+/- list of names and groups)]
create or display groups of persons used in purchase command
[date] purchase Person itemName amount (+/- list of names and groups)
a person purchases an item for an amount, which must be spread in the resolved group. A possible cents remainder of N cents from splitting division is spread between the first N persons in the list ordered by name, each person pays an extra 0.01.
secretSanta GROUPNAME
random gift assignment in a group with rules: No-one should be assigned to get a gift for themselves in groups larger than 1 person; Gift pairs cannot be reciprocal in groups larger than 2 people: in other words, you can't get a gift from a person and give a gift to the same person
[date] cashback Person itemName amount [(list of [+|-] persons | GROUPS)]
a commitment to refund some expense to a group, splitting it exactly between members with the same logic as in purchase.
[date] writeOff
clear all transactions (in the database) before and including the given limit date (default today).
help
print the list of commands in natural sorted order
exit
Have fun!
Project was completed on 18.07.22.
23.06.22 Project started.
26.06.22 Stage 1 completed with Spring Boot CommandLineRunner implementation, Command Pattern used with CommandLineInterpreter and LineCommand Interface, Mockito Inorder Integration tests
27.06.22 Stage 2 completed, further commands added for groups creating and splitting, also now transferred from integer transaction amounts to real money arithmetic on cents basis with rounding etc.
30.06.22 Stage 3 completed, complicated group commands of adding, removing persons and groups added for use in purchase commands. Streaming and groupingBy collectors applied.
12.07.22 Stage 4 completed, a lot of new functionality: secretSanta, cashBack and writeOff commands added, H2 database with @ManyToMany, @Transactional, FetchType.Lazy vs Eager, CascadeType.MERGE etc.. Native @Query for Join select.
17.07.22 Stage 5 completed, balance command gets additional arguments to filter on persons, which have to be resolved in the same way as done for purchase, cashBack and group add/remove commands
18.07.22 Final Stage 6 completed, implement clever algorithm (class BalanceOptimizer) to reduce minimum repayments / settlements amongst the group of involved persons in the transactions.