[Z Blog] Qbit servlet support also a preview of using jetty and the QBit microservice lib together

I have a prototype that uses Jetty to prove out that qbit and Servlets is working for REST support.

Simple Service

Simple Service and Service Server construction

package io.advantageous.qbit.servlet.integrationproto;
import io.advantageous.qbit.annotation.RequestMapping;
import io.advantageous.qbit.http.HttpServer;
import io.advantageous.qbit.server.ServiceEndpointServer
ServiceEndpointServer
ServiceEndpointServer;
import static io.advantageous.qbit.server.EndpointServerBuilder.endpointServerBuilder;

/**
 * Created by rhightower on 2/12/15.
 */
public class MyServiceModule {
    @RequestMapping("/ping")
    public static class PingService {

        @RequestMapping("/ping")
        public String ping() {
            return "ok";
        }
    }

    public static ServiceEndpointServer
ServiceEndpointServer
ServiceEndpointServer configureApp(final HttpServer server) {
        return endpointServerBuilder().setHttpServer(server)
                .build().initServices(new PingService()).startServer();
    }
}

The above by design has nothing to do with Jetty or Servlets.

Then to bind it into a Servlet engine for testing, I use Jetty because Jetty is easy to use and embed.

Using Jetty to test QBit servlet support

package io.advantageous.qbit.servlet.integrationproto;
import io.advantageous.qbit.http.HttpServer;
import io.advantageous.qbit.server.ServiceEndpointServer
ServiceEndpointServer
ServiceEndpointServer;
import io.advantageous.qbit.servlet.QBitHttpServlet;
import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.servlet.ServletContextHandler;
import javax.servlet.ServletConfig;

/**
 * Created by rhightower on 2/12/15.
 */
public class QBitPlusJettyPrototype {

    public static class MyQBitServlet extends QBitHttpServlet {
        public static final String QBIT_SERVICE_SERVER_SERVER = "QBit.ServiceEndpointServer
ServiceEndpointServer
ServiceEndpointServer.server";
        private ServletConfig config;

        @Override
        protected void wireHttpServer(final HttpServer httpServer, final ServletConfig config) {
            final ServiceEndpointServer
ServiceEndpointServer
ServiceEndpointServer server = MyServiceModule.configureApp(httpServer);
            config.getServletContext().setAttribute(QBIT_SERVICE_SERVER_SERVER, server);
            this.config = config;
        }

        @Override
        protected void stop() {
            final ServiceEndpointServer
ServiceEndpointServer
ServiceEndpointServer server =
                    (ServiceEndpointServer
ServiceEndpointServer
ServiceEndpointServer)
                            config.getServletContext().getAttribute(QBIT_SERVICE_SERVER_SERVER);
            server.stop();
        }
    }

    public static void main(String... args) throws Exception {
        Server server = new Server(8080);
        ServletContextHandler servletContextHandler = new ServletContextHandler(server,
                                                                       "*", true, false);
        servletContextHandler.addServlet(MyQBitServlet.class, "/services/*");
        server.start();
        server.join();
    }
}

We just start up Jetty. Tell Jetty that it is a Servlet container. We create a servlet that extends QBitHttpServlet (that is the cross platform way to use QBit in any container, yes.. you could use QBit in Tomcat or Undertow or... God Forbid Websphere or WebLogic).

The support classes for QBit / Servlet support are:

• QBitHttpServlet template design pattern to hook into Servlet lifecycle
• QBitServletUtil utility to convert from HttpServletRequest to QBit HttpRequest
• HttpServletParamMultiMap adapter to a multi-map from a servlet request
• HttpServletHeaderMultiMap ditto but for headers (painful but lightweight)
• ServletHttpServer lightweight HttpServer (this could be in core, it is wafer thin)

Implementation (Early)

I want to put this in qbit-core. It has no ties to Servlets at all.

ServletHttpServer

package io.advantageous.qbit.servlet;

import io.advantageous.qbit.http.HttpRequest;
import io.advantageous.qbit.http.HttpServer;
import io.advantageous.qbit.http.WebSocketMessage;

import java.util.concurrent.*;
import java.util.function.Consumer;
import java.util.function.Predicate;

/**
 * Created by rhightower on 2/12/15.
 */
public class ServletHttpServer implements HttpServer {

    private Consumer<WebSocketMessage> webSocketMessageConsumer = webSocketMessage -> {

    };
    private Consumer<WebSocketMessage> webSocketCloseMessageConsumer = webSocketMessage -> {

    };
    private Consumer<HttpRequest> httpRequestConsumer = request -> {

    };
    private Consumer<Void> requestIdleConsumer = aVoid -> {};
    private Consumer<Void> webSocketIdleConsumer = aVoid -> {};
    private Predicate<HttpRequest> shouldContinueHttpRequest = request -> true;
    private ScheduledFuture<?> future;

    @Override
    public void setShouldContinueHttpRequest(Predicate<HttpRequest> predicate) {
        this.shouldContinueHttpRequest = predicate;
    }

    public void handleRequest(final HttpRequest request) {
        if (shouldContinueHttpRequest.test(request)) {
            httpRequestConsumer.accept(request);
        }
    }

    @Override
    public void setWebSocketMessageConsumer(final Consumer<WebSocketMessage> webSocketMessageConsumer) {
        this.webSocketMessageConsumer = webSocketMessageConsumer;
    }

    @Override
    public void setWebSocketCloseConsumer(Consumer<WebSocketMessage> webSocketCloseMessageConsumer) {
        this.webSocketCloseMessageConsumer = webSocketCloseMessageConsumer;
    }

    @Override
    public void setHttpRequestConsumer(Consumer<HttpRequest> httpRequestConsumer) {
        this.httpRequestConsumer = httpRequestConsumer;
    }

    @Override
    public void setHttpRequestsIdleConsumer(Consumer<Void> idleConsumer) {
        this.requestIdleConsumer = idleConsumer;
    }

    @Override
    public void setWebSocketIdleConsume(Consumer<Void> idleConsumer) {

        this.webSocketIdleConsumer = idleConsumer;
    }

    private ScheduledExecutorService monitor;

    @Override
    public void start() {


        monitor = Executors.newScheduledThreadPool(1,
                runnable -> {
                    Thread thread = new Thread(runnable);
                    thread.setName("ServletHttpServer Flush Thread" );
                    return thread;
                }
        );

        /** This wants to be configurable. */
        future = monitor.scheduleAtFixedRate(() -> {
            try {
                requestIdleConsumer.accept(null);
                webSocketIdleConsumer.accept(null);
            } catch (Exception ex) {
                ex.printStackTrace();
                //logger.error("blah blah Manager::Problem running queue manager", ex); //TODO log this
            }
        }, 50, 50, TimeUnit.MILLISECONDS);


    }

    @Override
    public void stop() {

        if (future!=null) {
            future.cancel(true);
        }

        if (monitor!=null) {
            monitor.shutdown();
        }
    }
}

A Servlet so someone using Servlets can easily use QBit.

QBitHttpServlet - allows QBit REST to be easily used from Servlets

package io.advantageous.qbit.servlet;

import io.advantageous.qbit.http.HttpRequest;
import io.advantageous.qbit.http.HttpServer;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

import static io.advantageous.qbit.servlet.QBitServletUtil.convertRequest;

/**
 * Created by rhightower on 2/12/15.
 */
@WebServlet(asyncSupported = true)
public abstract class QBitHttpServlet extends HttpServlet {

    private final ServletHttpServer httpServer = new ServletHttpServer();

    @Override
    public void destroy() {
        httpServer.stop();
        stop();
    }

    protected abstract void stop();

    @Override
    public void init(ServletConfig config) throws ServletException {
        httpServer.start();
        wireHttpServer(httpServer, config);
    }

    protected abstract void wireHttpServer(final HttpServer httpServer, ServletConfig config);

    @Override
    protected void service(final HttpServletRequest request, final HttpServletResponse response)
                                                             throws ServletException, IOException {
        final HttpRequest httpRequest = convertRequest(request.startAsync());
        httpServer.handleRequest(httpRequest);
    }
}

Now the meat. This does all the work and glue. This glues the Servlet world to the QBit world.

QBitServletUtil GLUE

package io.advantageous.qbit.servlet;

import io.advantageous.qbit.http.HttpRequest;
import io.advantageous.qbit.http.HttpRequestBuilder;
import io.advantageous.qbit.util.MultiMap;
import org.boon.IO;

import javax.servlet.AsyncContext;
import javax.servlet.ServletInputStream;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import java.io.IOException;
import java.nio.charset.StandardCharsets;

import static io.advantageous.qbit.http.HttpRequestBuilder.httpRequestBuilder;

/**
 * Created by rhightower on 2/12/15.
 */
public class QBitServletUtil {

    public static HttpRequest convertRequest(final AsyncContext asyncContext) {

        final HttpServletRequest request = (HttpServletRequest) asyncContext.getRequest();
        final HttpServletResponse response = (HttpServletResponse) asyncContext.getResponse();
        final MultiMap<String, String> headers = new HttpServletHeaderMultiMap(request);
        final MultiMap<String, String> params = new HttpServletParamMultiMap(request);
        final HttpRequestBuilder httpRequestBuilder =
                                    httpRequestBuilder().setParams(params)
                                        .setHeaders(headers).setUri(request.getRequestURI())
                                        .setMethod(request.getMethod());

        setRequestBodyIfNeeded(request, httpRequestBuilder);
        setupRequestHandler(asyncContext, response, httpRequestBuilder);
        return httpRequestBuilder.build();
    }

    private static void setupRequestHandler(AsyncContext asyncContext, HttpServletResponse response, HttpRequestBuilder httpRequestBuilder) {
        httpRequestBuilder.setTextResponse((code, contentType, body) -> {
            response.setHeader("Content-Type", contentType);
            try {
                final ServletOutputStream outputStream = response.getOutputStream();
                IO.write(outputStream, body);
                outputStream.close();
                asyncContext.complete();
            } catch (IOException e) {
               throw new IllegalStateException(e);
            }
        });
    }

    private static void setRequestBodyIfNeeded(HttpServletRequest request, HttpRequestBuilder httpRequestBuilder) {
        if (request.getMethod().equals("POST") || request.getMethod().equals("PUT")) {
            final String body = readBody(request);
            if (body!=null) {
                httpRequestBuilder.setBody(body);
            }
        }
    }

    private static String readBody(HttpServletRequest request) {
        try {
            final ServletInputStream inputStream = request.getInputStream();
            final String body = IO.read(inputStream, StandardCharsets.UTF_8);
            return body;
        } catch (IOException e) {
            throw new IllegalStateException(e);
        }
    }
}