APP-database-hook

This database hook is responsible for fetching data from 3rd party APIs. It also provides an SSE for an application to attach listeners to, so they can receive updates when new data is available. It uses Hibernate and Spring WebFlux.

Video

Click below to see our video for the app.

Setup

1. The database must first be loaded before running the database hook. More instructions can be found here.
2. Add the MINTS_BUCKET, MINTS_ORG, MINTS_TOKEN, MINTS_URL, and OPENWEATHER_TOKEN environment variables. IntelliJ has native support for this if you edit the configuration settings. More detailed information on how to add environment variables to your IntelliJ run configurations can be found here.

Server-Sent Events (SSE)

The APP-database-hook comes with a Server-Sent Event stream to listen for when sensor data has been updated. The SSE can be subscribed to for listeners to know when data has been updated. The SSE is located at /sse, with an endpoint to connect to after (i.e. /sse/sensor). The port is at port 8081.

Below is an example of an SSE listener in Java using Spring WebFlux:

WebClient client = WebClient.create("http://localhost:8081/sse");
ParameterizedTypeReference<ServerSentEvent<SensorUpdate>> type = new ParameterizedTypeReference<>() {};

Flux<ServerSentEvent<SensorUpdate>> eventStream = client.get()
    .uri("/sensor")
    .retrieve()
    .bodyToFlux(type);

eventStream.subscribe(
    sse -> System.out.println("Received: " + sse.data()),
    err -> System.err.println("Error: " + err),
    () -> System.out.println("Done")
);

Problem Troubleshooting

Q: For some weird reason, the program just pauses execution on a line in FetchDataTask.

A: There is a glitch currently where FetchDataTask does not output errors. So, if you are running the program and it pauses on a line in FetchDataTask, it is most likely because there is an error. To fix this, you can add a breakpoint on the line that it is pausing on and run the program in debug mode. This will allow you to see the line that is pausing. Then, you can move the code to Main.java to see the error.

It's quite a bad solution really, so it might be worth looking into why errors don't output. Perhaps it's because of ScheduledExecutorService?