Widgets

REST API for CRUD operation on widgets. The project is built with

Java 11
Spring Boot 2.3.3
H2 in memory DB

Build and run

Run Unit and Integration tests

mvn clean test

Build the project

mvn clean install

Launch the server

mvn spring:boot run

Server is launched on port 8080

REST API documentation

Create a new widget

For testing the API I used Postman. Alternatively curlcommand works as well.

POST Request http://localhost:8080/widgets

Get widget by identifier

GET Request http://localhost:8080/widgets/{id}

Update widget by ID

PUT Request http://localhost:8080/widgets/{id}

Delete widget by ID

DELETE Request http://localhost:8080/widgets/{id}

Solution approach

I used Spring HATEOAS project library in order to create a REST representation that follows the principle of HATEOAS.
For the in memory storage approach (non H2) I chose to represent the data in a TreeMap data structure. Reasoning behind my choice:
- I used zIndex as a key for the TreeMap implementation in order to have the widgets sorted by zIndex.
- Regarding time-space complexity I weighed in the possibility of using an extra map which would have the Widget ID as key. That implies more space for better time for operations like widget lookups. I assumed that read/write operations are not as many as widgets are being created so I chose to use less space for a slight increase in lookup time.

Complexities implemented:

Pagination
SQL Database - for this I chose H2 in memory database. The configuration to switch between in memory storage using a TreeMap or H2 database is done by setting storage.h2inside application.properties to true for using H2 DB or false for using TreeMap in memory storage. To access the H2 console use http://localhost:8080/h2-console username sa and no password. Data source URL is jdbc:h2:mem:widget.

Note:

For filtering challenge, I considered using Two Dimensional Binary Indexed Tree or Fenwick Tree as data structure in order to obtain a better time complexity than O(n). Given that this is a new data structure for me I didn't have enough time to implement a solution however I greatly enjoyed getting familiar with it.

andreivisan/widgets