Daily Mail Subscription Service

/subscription/create
- Takes an email-address in the request body and subscribes the provided email-address to the daily mail subscription service
- If subscribed at 11:47pm, the user will recieve a mail every day at the same time i.e 11:47pm via dynamic cron expressions
- If Already subscribed, EmailAlreadyRegisteredException is thrown
- A Quartz Trigger is created with the email-address being the identity (so that same email-address can not be subscribed twice) and added to a Quartz job responsible for sending the daily mail when the trigger is fired.
/subscription/status/{emailId}
- Tells if the provided emailId is registered to the daily mail subsription service i.e a trigger with identity same as the email address is scheduled with the created Quartz job
/subscription/cancel/{emailId}
- Unsubscribes the provided emailId from daily mail subscription service if it's registered i.e unschedules the trigger with identity same as the email address from the created Quartz Job

Main classes and working flow

DailySubscriptionMailSenderJob.java
- Implements the Quartz Job interface and overrides execute(JobExecutionContext context) method
- execute() method will be executed whenever a trigger registered to the job is fired
- The method extracts the emailId from the JobExecutionContext and uses it to send mail to the user
DailyMailSubscriptionTriggerFactory.java
- has a single generateTrigger() that takes in an emailAddress and returns a trigger for the above created job with identity as the same email-address
- the created trigger is assigned a dynamic cron expression that will make the trigger fire exactly 24 hours to the current time
DailyMailSubscriptionScheduler.java
- Exposes methods to
  - Start the scheduler and assign the above created Job (Called during application startup by DailyMailSchedulerInitializer.java)
  - Add a new trigger to the scheduler
  - Remove a trigger with the scheduler
  - method returning boolean corresponding to whether trigger with identity same as provided emailId is registered with the scheduler.

Recommended way is to use sdkman for installing both maven and java

Run the below commands in the core

mvn clean

mvn install

Execute any of the two commands below to run the application

java -jar target/daily-mail-quartz-scheduler-spring-boot-0.0.1-SNAPSHOT.jar

mvn spring-boot:run

The Default port is 8080 and base-url is set to /mercury (both can be changed in application.properties)

Go to the below URI to view Swagger-UI (API-docs)

http://localhost:8080/mercury/swagger-ui.html