Learning App - Assignment Complete

An Upwork assignment to demonstrate REST API

Index

• Code Structure
• Data
• Spring Framework Components
• Open Source Libraries
• Build
• Javadocs
• Application Server
• Run
• APIs
• REST Console
• cURL
• Technology choice
• Configuration

Code Structure

The code in this assignment is arranged in the below folder structure

├── com.learning.app          # The root package
    ├── api                   # This package contains all the APIs 
    ├── exceptions            # This package contains all the exceptions that arise in the application
    ├── models                # This package contains all the value objects
    ├── repository            # This package contains all the Data access 
    ├── service               # This package contains all the business logic
    └── utils                 # This package contains all the utility classes used for this assignment

Please refer to Javadocs section on generating a detailed explanation of the code

Data

The sample data for this application is scraped (using Selenium) from Udemy. The courses name, description and pricing is kept in a course.json file in resources folder

Spring Framework Components

• Spring Boot - The core library for bootstrapping the entire application (Uses Tomcat 9 as default)
• Spring Web - For exposing REST Endpoints
• Spring JDBC Template - For Data access

Open Source Libraries

Apart from Spring Boot and other Spring dependencies, this assignment uses the below open source libraries

• Project Lombok - Lombok is used to avoid boilerplate code like getters/setter/toString/hashCode/default constructors etc. More details about Project lombok can be found here: Project Lombok
• H2 - The in-memory database. The H2 database can be used in different modes like File, In-Memory, TCP etc. I have chosen the In-Memory style database for faster access. The data is destroyed when the application is shutdown. The data is populated again during the application startup
• commons-io - The Apache commons IO library has been used to read the course.json file and other file operations
• Springfox Swagger2 and springfox-swagger-ui - These libraries are used to generate the Swagger documentation of the APIs

Build

To build the project follow the below instructions. Go to the root of the application and give the command:

mvn clean package

After successful execution, there will be a folder called target at the root of the project. The target folder contains the executable jar learning-app.jar

As part of the build's package goal, a plugin to generate javadocs for the assignment runs. This plugin generates Javadocs for the entire application code. Refer Javadocs section for more information

Javadocs

After successful build, in the target folder, there will be a folder called apidocs. This apidocs folder contains the Javadocs in HTML format. Click on index.html (that is available in the apidocs folder) to navigate through the Javadocs

Application Server

Spring Boot 2.x by default comes with Apache Tomcat 9.x. So, for this App, the default Tomcat provided by the Spring Boot has been used (without any tuning)

Run

To start the application follow the below instructions

• Go to target folder
• Issue the command :

java -Dspring.config.location=<LOCATION_OF_application.yml>-jar learning-app.jar

Example: java -Dspring.config.location=C:/application.yml-jar learning-app.jar 

By default, the application starts on the port specified in the application.yml file (which is 18080).

Note the default port can be overridden using the options -Dserver.port

To start the server on a different port

java -Dserver.port=XXXXX  -Dspring.config.location=<LOCATION_OF_application.yml>-jar learning-app.jar
Example: java -Dserver.port=19090  -Dspring.config.location=C:/applicatiton.yml -jar learning-app.jar

APIs

The supported APIS are :

• getCourse - HTTP GET - Get course details for a given Course Id
• getAllCourses - HTTP GET - Get all the avaialble course details
• createCourse - HTTP POST - Create a new course
• deleteCourse - HTTP DELETE - Delete a course

For the payloads and the URL, Check REST Console section below

REST Console

The APIs are Swagger-Enabled. That is, the APIs can be tested and the API documentation can be read online. To read and test the APIs using Swagger console follow the below instructions :

• Start the server as mentioned in Run section

• Open a browser to http://host:port/swagger-ui. Example : http://localhost:18080/swagger-ui

• If everything is OK, you have a screenshot similar to :

  

cURL

Use the below curl commands to access the APIs

Replace the HOST with the host where the application is deployed and PORT with the port that the server is listening on. COURSE_ID can be any number from 1 to 400

• getCourse - Get course details for a particular Course ID

curl -X GET "http://HOST:PORT/api/v1/courses/COURSE_ID" -H  "accept: application/json"
Example: curl -X GET "http://localhost:18080/api/v1/courses/100" -H  "accept: application/json"

• getAllCourses - Get all the courses available in the system

curl -X GET "http://HOST:PORT/api/v1/courses" -H  "accept: application/json"
Example: curl -X GET "http://localhost:18080/api/v1/courses" -H  "accept: application/json"

• deleteCourse - Delete course details for a particular Course ID

curl -X DELETE "http://HOST:PORT/api/v1/courses/COURSE_ID" -H  "accept: application/json"
Example: curl -X DELETE "http://localhost:18080/api/v1/courses/1" -H  "accept: application/json"

• createCourse - Creates a new course

curl -X POST "http://HOST:PORT/api/v1/courses/COURSE_ID" -H  "accept: application/json" -H "content-type: application/json" -d JSON_BODY
Example: curl -X POST "http://localhost:18080/api/v1/courses" 
-H  "accept: application/json" 
-H  "Content-Type: application/json" 
-d "{  \"description\": \"new course\",  \"name\": \"new course\",  \"pricing\": {    \"cess\": 10.0,    \"cost\": 2,    \"discount\": 1,    \"gst\": 0,    \"strategies\": [      \"Free\"    ]  }}"

Technology choice

The technology stack used for this assignment has been chosen keeping in mind the below points

• Simple - Since this is just an assignment used to develop a single API, I chose to keep the technology stack simple 😄 . For example, for data access, JPA could be used instead of JDBC Template
• Clean - Wanted to keep the code clean and minimal. For example, to support HATEOAS it would have required an additional dependency and more code would have been required.
• Faster Development - Since this is a competition, the focus was to develop faster
• Data source - The datasource chosen for the assignment was a simple H2 database. For a real application we could choose a better In-Memory databases like Redis. Also since the requirement is to keep the data dynamic with minimal changes to the user-interface, we can consider using a NOSQL database like MongoDB

Configuration

The application configuration (application.yml) can be found in resources folder. The file contains 2 profiles

• Development
• Production

The default profile is Development. So all the configurations required for this profile have been configured and the configurations required for Production profile has been ignored. The configurations are self-explained. For more information, please refer Spring Configuration guide.

Apart from Spring configurations, the below are the additional configurations that are used for the assignment

pricing:
  strategies: Free, One-Time, Subscription

The above configuration is created for the below requirement :

There should be a global configuration that should be used in cases courses have not added their overrides.

So, to demonstrate the above requirement, if the course does not have a pricing strategy, I am filling the strategy with above three options