Clojure is a passionate language that uses strong mathematical expressions for you to write code. While I am not a language expert, in any language, in fact, I have a general profile. Therefore, I decided to create a small banking application for studying and testing purposes.

Before begin, I have three book recommendations:

• Practical Clojure By VanderHart, Luke
• Professional Clojure By Jeremy Anderson
• Clojure for the Brave and True

Tools

My Dexter’s labs:

I’ve used Clojure with Leiningen and use the Emacs editor that perfectly matches with Clojure. For more information check out this page.

1. Project Design

The idea of the small bank is to create a Rest API using Clojure where the user can:

• Create a new account if there is no
• The user can put money into this account
• The user can withdraw money from the account
• The multi-threaded system controls the concurrency of multiple concurrent accesses
• The operation is using a Rest API
• Check account balance

Start

I did tests on the FreeBSD/Mac OS and Ubuntu operating systems. You can download the project:

git clone https://github.com/edersoncorbari/small-bank.git

Now, you need to raise the HTTP server.

./launch-app

By default, the server uses port 3000. On another terminal, run the curl response test:

./launch-curl

You should get the following outputs in response:

-------------------------------------------------------------------------------------
*** Simple Rest API to Check/Balance Small-Bank ***

Please use the (curl-api-test) script for testing.
-------------------------------------------------------------------------------------
Add money account: 1 -> Crediting: 316.22776601683793319988
:> Successful transaction
Add money account: 2 -> Crediting: 447.21359549995793928183
:> Successful transaction
Add money account: 3 -> Crediting: 547.72255750516611345696
:> Successful transaction
Add money account: 4 -> Crediting: 632.45553203367586639977
:> Successful transaction
Add money account: 5 -> Crediting: 707.10678118654752440084
:> Successful transaction
Add money account: 6 -> Crediting: 774.59666924148337703585
:> Successful transaction
Add money account: 7 -> Crediting: 836.66002653407554797817
:> Successful transaction
Add money account: 8 -> Crediting: 894.42719099991587856366
:> Successful transaction
Add money account: 9 -> Crediting: 948.68329805051379959966
:> Successful transaction
Add money account: 10 -> Crediting: 1000.00000000000000000000
:> Successful transaction
Add money account: 11 -> Crediting: 1048.80884817015154699145
:> Successful transaction
Add money account: 12 -> Crediting: 1095.44511501033222691393
:> Successful transaction
Add money account: 13 -> Crediting: 1140.17542509913797913604
:> Successful transaction
Add money account: 14 -> Crediting: 1183.21595661992320851346
:> Successful transaction
Add money account: 15 -> Crediting: 1224.74487139158904909864
:> Successful transaction

-------------------------------------------------------------------------------------
Get balance account: 1
{"account":1,"date":"2018-11-04T18:27:18.915-03:00","balance":316.22776601683796}
Get balance account: 2
{"account":2,"date":"2018-11-04T18:27:18.929-03:00","balance":447.21359549995793}
Get balance account: 3
{"account":3,"date":"2018-11-04T18:27:18.939-03:00","balance":547.7225575051662}
Get balance account: 4
{"account":4,"date":"2018-11-04T18:27:18.949-03:00","balance":632.4555320336759}
Get balance account: 5
{"account":5,"date":"2018-11-04T18:27:18.961-03:00","balance":707.1067811865476}
Get balance account: 6
{"account":6,"date":"2018-11-04T18:27:18.972-03:00","balance":774.5966692414834}
Get balance account: 7
{"account":7,"date":"2018-11-04T18:27:18.982-03:00","balance":836.6600265340755}
Get balance account: 8
{"account":8,"date":"2018-11-04T18:27:18.993-03:00","balance":894.4271909999159}
Get balance account: 9
{"account":9,"date":"2018-11-04T18:27:19.004-03:00","balance":948.6832980505138}
Get balance account: 10
{"account":10,"date":"2018-11-04T18:27:19.017-03:00","balance":1000.0}
Get balance account: 11
{"account":11,"date":"2018-11-04T18:27:19.026-03:00","balance":1048.8088481701516}
Get balance account: 12
{"account":12,"date":"2018-11-04T18:27:19.041-03:00","balance":1095.4451150103323}
Get balance account: 13
{"account":13,"date":"2018-11-04T18:27:19.056-03:00","balance":1140.175425099138}
Get balance account: 14
{"account":14,"date":"2018-11-04T18:27:19.066-03:00","balance":1183.2159566199232}
Get balance account: 15
{"account":15,"date":"2018-11-04T18:27:19.083-03:00","balance":1224.744871391589}

-------------------------------------------------------------------------------------
Remove money account: 1 -> Debting: 31.62277660168379331998
:> Successful transaction
Remove money account: 2 -> Debting: 44.72135954999579392818
:> Successful transaction
Remove money account: 3 -> Debting: 54.77225575051661134569
:> Successful transaction
Remove money account: 4 -> Debting: 63.24555320336758663997
:> Successful transaction
Remove money account: 5 -> Debting: 70.71067811865475244008
:> Successful transaction
Remove money account: 6 -> Debting: 77.45966692414833770358
:> Successful transaction
Remove money account: 7 -> Debting: 83.66600265340755479781
:> Successful transaction
Remove money account: 8 -> Debting: 89.44271909999158785636
:> Successful transaction
Remove money account: 9 -> Debting: 94.86832980505137995996
:> Successful transaction
Remove money account: 10 -> Debting: 100.00000000000000000000
:> Successful transaction
Remove money account: 11 -> Debting: 104.88088481701515469914
:> Successful transaction
Remove money account: 12 -> Debting: 109.54451150103322269139
:> Successful transaction
Remove money account: 13 -> Debting: 114.01754250991379791360
:> Successful transaction
Remove money account: 14 -> Debting: 118.32159566199232085134
:> Successful transaction
Remove money account: 15 -> Debting: 122.47448713915890490986
:> Successful transaction

-------------------------------------------------------------------------------------
Get balance account: 1
{"account":1,"date":"2018-11-04T18:27:19.359-03:00","balance":284.604989415154167}
Get balance account: 2
{"account":2,"date":"2018-11-04T18:27:19.372-03:00","balance":402.492235949962134}
Get balance account: 3
{"account":3,"date":"2018-11-04T18:27:19.382-03:00","balance":492.950301754649586}
Get balance account: 4
{"account":4,"date":"2018-11-04T18:27:19.394-03:00","balance":569.209978830308315}
Get balance account: 5
{"account":5,"date":"2018-11-04T18:27:19.405-03:00","balance":636.39610306789284}
Get balance account: 6
{"account":6,"date":"2018-11-04T18:27:19.416-03:00","balance":697.13700231733506}
Get balance account: 7
{"account":7,"date":"2018-11-04T18:27:19.429-03:00","balance":752.99402388066794}
Get balance account: 8
{"account":8,"date":"2018-11-04T18:27:19.440-03:00","balance":804.98447189992431}
Get balance account: 9
{"account":9,"date":"2018-11-04T18:27:19.450-03:00","balance":853.81496824546243}
Get balance account: 10
{"account":10,"date":"2018-11-04T18:27:19.463-03:00","balance":900.0}
Get balance account: 11
{"account":11,"date":"2018-11-04T18:27:19.473-03:00","balance":943.92796335313644}
Get balance account: 12
{"account":12,"date":"2018-11-04T18:27:19.483-03:00","balance":985.90060350929907}
Get balance account: 13
{"account":13,"date":"2018-11-04T18:27:19.494-03:00","balance":1026.1578825892242}
Get balance account: 14
{"account":14,"date":"2018-11-04T18:27:19.503-03:00","balance":1064.89436095793088}
Get balance account: 15
{"account":15,"date":"2018-11-04T18:27:19.513-03:00","balance":1102.27038425243009}

The above test adds new accounts, then checks the balance, and then takes money out of the accounts. You can see more details of the implementation by looking at the project’s README file.

Considerations

This is project is only used for studies using Clojure, developed by layman in the subject, and perhaps not one of the best implementations, techniques, and uses of the language. 

I am always open to feedback, so free feel to let me know what you think in the comments below.