How do I configure Jetty to allow larger forms when used with Spark Framework

How do I configure Jetty options via Spark framework ?

Im getting the problem below when i submit a large form. The solution for Jetty is documented at Form too Large Exception

But Jetty is hidden from me using Spark Framework, how would I configure to resolve this.

    org.eclipse.jetty.http.BadMessageException: 400: Unable to parse form content
        at org.eclipse.jetty.server.Request.getParameters(Request.java:373)
        at org.eclipse.jetty.server.Request.getParameter(Request.java:1016)
        at javax.servlet.ServletRequestWrapper.getParameter(ServletRequestWrapper.java:194)
        at spark.Request.queryParams(Request.java:283)
        at spark.http.matching.RequestWrapper.queryParams(RequestWrapper.java:141)
        at com.jthink.songkong.server.callback.ServerEditSongs.startTask(ServerEditSongs.java:45)
        at com.jthink.songkong.server.CmdRemote.lambda$null$62(CmdRemote.java:171)
        at spark.RouteImpl$1.handle(RouteImpl.java:72)
        at spark.http.matching.Routes.execute(Routes.java:61)
        at spark.http.matching.MatcherFilter.doFilter(MatcherFilter.java:130)
        at spark.embeddedserver.jetty.JettyHandler.doHandle(JettyHandler.java:50)
        at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:1568)
        at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:141)
        at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:132)
        at org.eclipse.jetty.server.Server.handle(Server.java:564)
        at org.eclipse.jetty.server.HttpChannel.handle(HttpChannel.java:317)
        at org.eclipse.jetty.server.HttpConnection.onFillable(HttpConnection.java:251)
        at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:279)
        at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:110)
        at org.eclipse.jetty.io.ChannelEndPoint$2.run(ChannelEndPoint.java:124)
        at org.eclipse.jetty.util.thread.Invocable.invokePreferred(Invocable.java:128)
        at org.eclipse.jetty.util.thread.Invocable$InvocableExecutor.invoke(Invocable.java:222)
        at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.doProduce(EatWhatYouKill.java:294)
        at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.run(EatWhatYouKill.java:199)
        at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:673)
        at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:59
1)
        at java.lang.Thread.run(Thread.java:745)
    Caused by: java.lang.IllegalStateException: Form too large: 273433 > 200000
        at org.eclipse.jetty.server.Request.extractFormParameters(Request.java:516)
        at org.eclipse.jetty.server.Request.extractContentParameters(Request.java:454)
        at org.eclipse.jetty.server.Request.getParameters(Request.java:369)
        ... 26 more

Solution

A bit of history:

I looked up a little on the git repo of spark and found that this issue was raised on 3 Aug 2015, here issue 314
Perwendel (the guy maintaining Spark) added the Much wanted label on 11 Oct 2016
Then started working on it on 3 Nov 2016
He merged the Pull Request PR #813 to opens up possibility for any Jetty setting in Spark embedded.

I looked into the modifications added in this PR and I think you might be able to configure something by implementing the JettyServerFactory, if you overwrite the public Server create(...) method, you can return your custom Server:

public class Main {

  public static void main(String ...args) {
    CustomJettyServerFactory customJettyServerFactory = new CustomJettyServerFactory();
    EmbeddedServers.add(
        EmbeddedServers.Identifiers.JETTY, 
        new EmbeddedJettyFactory(customJettyServerFactory));
  }
}

class CustomJettyServerFactory implements JettyServerFactory {
  @Override
  public Server create(int maxThreads, int minThreads, int threadTimeoutMillis) {
    Server server = new Server();
    server.setAttribute("org.eclipse.jetty.server.Request.maxFormContentSize", 1000000);
    return server;
  }

  @Override
  public Server create(ThreadPool threadPool) {
    return null;
  }
}

Please have a try and see if you can make this work, I don't have anything setup to try it, but I think this is the correct path to configure your Jetty server.