This is provided as a possible starting point for a Java implementation. This code, based on Dropwizard, requires maven and Java 1.8.
Feel free to change everything.
mvn clean verify
java -jar target/9dt-backend-1.0-SNAPSHOT.jar server src/main/resources/local.yml
curl --header "Content-type: Application/json" -X POST http://localhost:8080/drop_token -d'{ "players":["p1", "p2"], "rows":4, "columns":4}'