Filters.java

import play.api.mvc.EssentialFilter;
import play.http.HttpFilters;
import util.HostFilter;

import javax.inject.Inject;

public class Filters implements HttpFilters {
    @Inject
    HostFilter hostFilter;

    @Override
    public EssentialFilter[] filters() {
        return new EssentialFilter[]{hostFilter};
    }
}

HostFilter.scala

import play.api.mvc._
import play.api.{Logger, Routes}
import play.api.libs.concurrent.Execution.Implicits.defaultContext
import play.api.Play

class HostFilter extends EssentialFilter {
  val host = Play.current.configuration.getString("swagger.api.host").getOrElse("")
  
  override def apply(nextFilter: EssentialAction) = new EssentialAction {
    def apply(requestHeader: RequestHeader) = {
      val newHeaders = requestHeader.headers.replace("Host" -> host) 
      val newRequest = requestHeader.copy(headers = newHeaders) 
      nextFilter(newRequest).map { result => 
        result
      }
    }
  }
}