How can a native Servlet Filter be used when using Spark web framework? - servlets

Question

I'm playing around with Spark (the Java web framework, not Apache Spark).
I find it really nice and easy to define routes and filters, however I'm looking to apply a native servlet filter to my routes and can't seem to find a way to do that.
More specifically, I would like to use Jetty's DoSFilter which is a servlet filter (contrast with the Spark Filter definition). Since Spark is using embedded Jetty, I don't have a web.xml to register the DoSFilter. However, Spark doesn't expose the server instance so I can't find an elegant way of registering the filter programatically either.
Is there a way to apply a native servlet filter to my routes?
I thought of wrapping the DoSFilter in my own Spark Filter, but it seemed like a weird idea.

Answer 1

You can do it like this:
public class App {
private static Logger LOG = LoggerFactory.getLogger(App.class);
public static void main(String[] args) throws Exception {
ServletContextHandler mainHandler = new ServletContextHandler();
mainHandler.setContextPath("/base/path");
Stream.of(
new FilterHolder(new MyServletFilter()),
new FilterHolder(new SparkFilter()) {{
this.setInitParameter("applicationClass", SparkApp.class.getName());
}}
).forEach(h -> mainHandler.addFilter(h, "*", null));
GzipHandler compression = new GzipHandler();
compression.setIncludedMethods("GET");
compression.setMinGzipSize(512);
compression.setHandler(mainHandler);
Server server = new Server(new ExecutorThreadPool(new ThreadPoolExecutor(10,200,60000,TimeUnit.MILLISECONDS,
new ArrayBlockingQueue<>(200),
new CustomizableThreadFactory("jetty-pool-"))));
final ServerConnector serverConnector = new ServerConnector(server);
serverConnector.setPort(9290);
server.setConnectors(new Connector[] { serverConnector });
server.setHandler(compression);
server.start();
hookToShutdownEvents(server);
server.join();
}
private static void hookToShutdownEvents(final Server server) {
LOG.debug("Hooking to JVM shutdown events");
server.addLifeCycleListener(new AbstractLifeCycle.AbstractLifeCycleListener() {
#Override
public void lifeCycleStopped(LifeCycle event) {
LOG.info("Jetty Server has been stopped");
super.lifeCycleStopped(event);
}
});
Runtime.getRuntime().addShutdownHook(new Thread() {
#Override
public void run() {
LOG.info("About to stop Jetty Server due to JVM shutdown");
try {
server.stop();
} catch (Exception e) {
LOG.error("Could not stop Jetty Server properly", e);
}
}
});
}
/**
* #implNote {#link SparkFilter} needs to access a public class
*/
#SuppressWarnings("WeakerAccess")
public static class SparkApp implements SparkApplication {
#Override
public void init() {
System.setProperty("spring.profiles.active", ApplicationProfile.readProfilesOrDefault("dev").stream().collect(Collectors.joining()));
AnnotationConfigApplicationContext ctx = new AnnotationConfigApplicationContext(ModocContext.class);
ctx.registerShutdownHook();
}
}}