About

This is a simple experiment, to wrap my mind around how Spring WebFlux works, loosely based on this guide and corresponding repo.

How's the weather?

Rather than just a simple "Hello, Spring!" echo, this project uses the weather.gov API to respond to latitude and longitude pairs with the corresponding 7-day forecast.

The WebClient is used to translate the (latitude,longitude) pair into a grid address from which the actual forecast can be found.

This requires a pair of API calls chained together, both of which are non-blocking:

Usage

Build and Run

To build and run this project from scratch, install both Java and Gradle via SDKMAN!:

sdk install java 11.0.6.hs-adpt
sdk install gradle 6.2.2

This enables you to build and run the server from the command line:

./gradlew clean build
./gradlew bootRun

> Task :bootRun

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.2.5.RELEASE)

2020-03-15 12:07:51.908  INFO 13318 --- [           main] o.papathanasiou.denis.ServerApplication  : Starting ServerApplication on localhost with PID 13318 (/.../spring-webflux/build/classes/java/main started by denis in /.../spring-webflux)
2020-03-15 12:07:51.913  INFO 13318 --- [           main] o.papathanasiou.denis.ServerApplication  : No active profile set, falling back to default profiles: default
2020-03-15 12:07:53.768  INFO 13318 --- [           main] o.s.b.web.embedded.netty.NettyWebServer  : Netty started on port(s): 8080
2020-03-15 12:07:53.778  INFO 13318 --- [           main] o.papathanasiou.denis.ServerApplication  : Started ServerApplication in 2.439 seconds (JVM running for 2.922)

Alternatively, you can just use IntelliJ IDEA, and turn on the ServerApplication run configuration.

Making Requests

Use curl or open a web browser and visit http://localhost:8080/weather/{latitude}/{longitude}.

For example, http://localhost:8080/weather/40.7688/-73.9898 on March 15, 2020 resulted in:

Time Period	Forecast
Today	Sunny. High near 52, with temperatures falling to around 49 in the afternoon. North wind around 8 mph.
Tonight	Mostly clear, with a low around 33. Northeast wind around 8 mph.
Monday	Mostly sunny, with a high near 45. East wind around 10 mph.
Monday Night	A chance of rain showers after 9pm. Mostly cloudy, with a low around 39. Southeast wind 7 to 10 mph. Chance of precipitation is 40%.
Tuesday	A chance of rain showers. Mostly cloudy, with a high near 56. South wind around 9 mph, with gusts as high as 21 mph. Chance of precipitation is 50%.
Tuesday Night	A slight chance of rain showers before midnight. Partly cloudy, with a low around 36.
Wednesday	Sunny, with a high near 48.
Wednesday Night	A slight chance of snow showers after midnight. Partly cloudy, with a low around 36.
Thursday	A chance of snow showers before 9am, then a chance of rain and snow showers. Mostly cloudy, with a high near 51. Chance of precipitation is 50%.
Thursday Night	A chance of rain showers. Mostly cloudy, with a low around 46. Chance of precipitation is 50%.
Friday	A chance of rain showers. Cloudy, with a high near 66. Chance of precipitation is 50%.
Friday Night	A chance of rain showers. Mostly cloudy, with a low around 45. Chance of precipitation is 40%.
Saturday	A chance of rain showers. Partly sunny, with a high near 51. Chance of precipitation is 30%.
Saturday Night	A slight chance of snow showers. Partly cloudy, with a low around 29.

Docker

The Dockerfile allows for running this application as a container.

With Docker Desktop (Mac, Windows) installed, build and tag the image like this, using the image build command:

docker image build -t spring-webflux:0.0.1 .

This should produce output similar to this, ending in a Successfully tagged message:

Sending build context to Docker daemon  26.68MB
Step 1/4 : FROM adoptopenjdk:11-jre-hotspot
11-jre-hotspot: Pulling from library/adoptopenjdk
...
[intermediate output elided]
...
Successfully tagged spring-webflux:0.0.1

To run the application image as a container:

docker container run --publish 8080:8080 --detach --name weather-report spring-webflux:0.0.1

The --detach command runs the container in the background.

The --publish command routes traffic from the external port to where the application expects it internally; in this case those are both 8080, but this could also be used to pick a different external value.

See the container run reference for more options.

While the container is running, a visit to http://localhost:8080/weather/40.7688/-73.9898 produces the same table of results.

To shut down the container, use this command, matching the --name from the previous step:

docker container rm --force weather-report