JAVA based Webserver for Code Challenge

This project is for a Code Challenge to develop a simple Webserver with the following requirements:

• The webserver should run on port 23456.

• The webserver has an endpoint at /api/encode.

• This endpoint should accept post requests.

• This endpoint expects a JSON string to be received. The JSON structure should have two keys.

• The JSON structure should have a key Shift. It’s value should be an integer.

• The JSON structure should have a key Message. It’s value should be a string.

• When the JSON payload is received, it should encode the provided message using the shift cipher method. If multiple words are provided, spaces should be retained.

• The shift cipher works by shifting each letter a given number of letters to the right in alphabet order. The letter A shifted 1 would be B. B shifted 2 would be D.

• If Shift = 3 and Message = “dad”, the encoded message would be generated as “gdg”.

• If Shift = 2 and Message = “the eagle has landed”, the encoded message would be generated as “vjg gcing jcu ncpfgf”.

• This should work for any positive shift value provided. If Shift = 522 and Message = “the eagle has landed”, the encoded message would be generated as “vjg gcing jcu ncpfgf”.

• When the message is successfully encoded, it should be stored in a file on disk.

• The endpoint should return a 200 if successful, 500 if unsuccessful.

• The endpoint should return a json object with a single key EncodedMessage. The value returned should be the string you successfully encoded. If unsuccessful, it should return an empty string.

Challenge Assumptions

The above challenge requirements do not specify the cipher character set, however based on the examples given it is assumed to be a 26 character set starting from lowercase 'a' and ending at lowercase 'z'. Due to this requirement no other character can be encoded, as such this application will throw an exception if any characters other than a through z or a space is provided. I did pre-process the data to lowercase the input such that it will handle captipal letters without throwing an exception.

Prerequisites

• Git
• Maven 3.6.3+
• Java8 JDK

Installing

1. Clone the repository - git clone https://github.com/hagak/webserver.git
2. Switch to the project directory
3. Issue 'mvn clean package' to build the jar file
4. Change directories to the <project>/target/ directory
5. Launch the server with 'java -jar webserver-1.0-SNAPSHOT-jar-with-dependencies.jar'

Testing

1. Create a JSON file to test following the requirements above. message.json is provide in the repo for testing
2. Execute 'curl -d @message.json -X POST http://127.0.0.1:23456/api/encode
3. The encoded message will be returned and a file named "cipher.txt" will be created in the same path as the path you launched the jar file from, most likely the target folder