Money Transfer REST API

Requirements:

Design a simple backend application that will handle the basics of an account manager and money transfer tool. The users should be able to:

• Create a new Account
• Delete an existing Account
• Deposit and Withdraw money from an Account
• Display all available Accounts
• Transfer money between Accounts.

The application should work in an multi-threaded environment and should validate the input data where needed.

Tools and libraries used:

• Java 8 as programming language
• Maven for build system
• Jetty for the embedded server
• Jersey for REST
• JUnit for testing

How to install and run the application

Go to project location and run from command line

mvn clean install
cd target
java -jar moneytransfer-1.0-SNAPSHOT-jar-with-dependencies.jar

API

View all accounts

Returns a JSON object containing a list of Account objects.

• URL /accounts
• Method GET
• Success Response - Code: 200

[
    {
        "id": "e6b068c4-788c-42e1-81db-35cf9815823e",
        "balance": 1523.51
    },
    {
        "id": "922ab185-a4a6-4c4a-a987-734f352c9ca1",
        "balance": 3259.64
    }
]

View Account information

Returns a JSON object containing an Account object.

• URL /accounts/{id}
• Method GET
• URL Parameters: id
• Example request: /accounts/e6b068c4-788c-42e1-81db-35cf9815823e
• Success Response - Code: 200

{
    "id": "e6b068c4-788c-42e1-81db-35cf9815823e",
    "balance": 1523.51
}

• Not found Response - Code: 404

Add new Account

Adds a new account in the data store and returns a JSON data containing the newly created account. The account will have balance 0.

• URL /accounts/
• Method POST
• Success Response - Code: 200

{
    "id": "b2cac407-c17d-41c2-9042-35208905dbb3",
    "balance": 0
}

Update an existing Account/Add a new Account

Updates or adds a new account in the data store (based on a JSON sent in the Body) and returns a JSON object containing the account.

• URL /accounts/
• Method PUT
• Body Parameters: JSON object representing account. Example:

{
    "id": "b2cac407-c17d-41c2-9042-35208905dbb3",
    "balance": 555
}

• Success Response - Code: 200

{
    "id": "b2cac407-c17d-41c2-9042-35208905dbb3",
    "balance": 555
}

Delete an existing Account

Returns a JSON object containing the deleted Account.

• URL /accounts/{id}
• Method DELETE
• URL Parameters: id
• Example request: /accounts/b2cac407-c17d-41c2-9042-35208905dbb3
• Success Response - Code: 200

{
    "id": "b2cac407-c17d-41c2-9042-35208905dbb3",
    "balance": 555
}

• Not found Response - Code: 404

Deposit money

Accepts a JSON object as parameter representing a Transfer object and returns a JSON object containing the updated Account.

• URL /deposit/
• Method PUT
• Body Parameters: JSON object representing the deposit. Example:

{
    "accountId": "e6b068c4-788c-42e1-81db-35cf9815823e",
    "amount": 100
}

• Success Response - Code: 200

{
    "id": "e6b068c4-788c-42e1-81db-35cf9815823e",
    "balance": 1623.51
}

• Bad request Response - Code: 400 In case input data is invalid.

Withdraw money

Accepts a JSON object as parameter representing a Transfer object and returns a JSON object containing the updated Account.

• URL /withdraw/
• Method PUT
• Body Parameters: JSON object representing the withdrawal. Example:

{
    "accountId": "e6b068c4-788c-42e1-81db-35cf9815823e",
    "amount": 100
}

• Success Response - Code: 200

{
    "id": "e6b068c4-788c-42e1-81db-35cf9815823e",
    "balance": 1523.51
}

• Bad request Response - Code: 400 In case input data is invalid or there are insufficient funds for this operation.

Transfer money between two accounts

Accepts a JSON object as parameter representing a Transfer object and returns a JSON object containing a list of the updated Accounts.

• URL /transfer/
• Method PUT
• Body Parameters: JSON object representing the transfer. Example:

{
    "accountId": "e6b068c4-788c-42e1-81db-35cf9815823e",
    "destinationId": "b2cac407-c17d-41c2-9042-35208905dbb3",
    "amount": 1000
}

• Success Response - Code: 200

[
    {
        "id": "e6b068c4-788c-42e1-81db-35cf9815823e",
        "balance": 623.51
    },
    {
        "id": "b2cac407-c17d-41c2-9042-35208905dbb3",
        "balance": 1000
    }
]

• Bad request Response - Code: 400 In case input data is invalid or there are insufficient funds for this operation.

Tests

To run unit tests simply run the following command

mvn test

The tests cover the exposed REST API calls with their expected input and output, as well as the interaction with the datastore layer, the model and the transfer service implementation itself taking into account the possibility of a multi-threaded environment.