Tiny money transfer server

Technologies

• Java 8
• Jetty web-server 9.4.19
• Jersey RESTful Web Services 2.29
• H2 database 1.4.199 (embedded mode)
• JUnit 5.5.0-M1
• Mockito 2.15.0

Description

RESTfull demo server simulates bank client and it's account and provides API for basic operations:

• Add new client
• View client's info
• Open account for client
• View account's info
• Debit account
• Withdraw from account
• Transfer certain amount of money from one account to other client account

All operations are done in parallel allowing multiple requests to the server at the same time.

Restrictions

• no authentication
• for the sake of simplicity one client can have only one account
• all supported currecies for account: EUR, USD, RUB
• all client/server communications are done using JSON object format
• data stored in in-memory database and lost after server restart

Transfer objects properties

Client data

• id - unique client id
• name - client name
• href - relative API path to client's info

Account data

• id - unique id of the account
• clientId - link to client id (owner of the account)
• currency - currency of the account
• amount - balance of the account
• href - relative API path to account's info

Debit/Withdraw data

• amountDiff - amount of money to debit (positive integer number) or withdraw (negative integer number) from account.

Transfer data

• srcAccountId - source account id to transfer money from
• dstAccountId - destination account id to transfer money to
• amount - amount to transfer

Error data

• code - unique code of the error
• msg - message of the error

List of errors

Code	Message
1	Client not found
2	Account not found
3	Internal SQL error
4	Client cannot be created
5	Client already exists
6	Client name must be provided
7	Currency must be provided to create an account
8	Client already has an account
9	Account cannot be created
10	Provided currency for account not supported
11	Client is not the owner of this account
12	Amount must be provided to update an account
13	Account cannot be updated
14	Insufficient amount to withdraw from account
15	Source account must be provided
16	Destination account must be provided
17	Amount to transfer must be provided
18	Source account not found
19	Destination account not found
20	Transfer must be done between different accounts
21	Currencies in accounts do not match
22	Amount to transfer must be a positive number
23	Error occurred while updating destination account
24	Error occurred while updating source account
25	Unexpected server error

Installation

Not required

Run functional tests

mvn verify -Pfailsafe

Run

mvn package
java -jar target/tinymoneytransfer-1.0.jar

Server starts on localhost at port 8080. Context root is /api

Endpoints

/clients - client and it's account opeartions

/transfers - transfer between 2 accounts

API paths

/clients

• POST - create new client using Client transport data

/clients/{clientId}

• GET - retrieve client info

/clients/{clientId}/account

• POST - create new client account

/clients/{clientId}/account/{accountId}

• GET - retrieve client account info
• POST - debit/withdraw from account using Debit/Withdraw transport data

/transfers

• POST - transfer money between accounts using Transfer transport data

Usage (sample commands using curl)

Create client

curl -d '{"name": "Bob"}' -H "Content-Type: application/json" -H "Accept: application/json" -X POST http://localhost:8080/api/clients

Respond:

{"id":1,"name":"Bob","href":"/clients/1"}

Client info

 curl -q -H "Content-Type: application/json" -H "Accept: application/json" -X GET http://localhost:8080/api/clients/1

Respond:

{"id":1,"name":"Bob","href":"/clients/1"}

Open an account for client

curl -d '{"currency":"EUR"}' -H "Content-Type: application/json" -H "Accept: application/json" -X POST http://localhost:8080/api/clients/1/account

Respond:

{"id":1,"clientId":1,"currency":"EUR","amount":0,"href":"/clients/1/account/1"}

Debit account

curl -d '{"amountDiff":"100"}' -H "Content-Type: application/json" -H "Accept: application/json" -X PUT http://localhost:8080/api/clients/1/account/1

Respond

{"id":1,"clientId":1,"currency":"EUR","amount":100,"href":"/clients/1/account/1"}

Transfer between accounts

curl -d '{"srcAccountId":"1", "dstAccountId":"2", "amount":"50"}' -H "Content-Type: application/json" -H "Accept: application/json" -X POST http://localhost:8080/api/transfers

Respond: no content