WebConfigurer.java

package com.mycompany.cevent.config;

import com.codahale.metrics.MetricRegistry;
import com.codahale.metrics.health.HealthCheckRegistry;
import com.codahale.metrics.servlet.InstrumentedFilter;
import com.codahale.metrics.servlets.MetricsServlet;
import com.mycompany.cevent.web.filter.CachingHttpHeadersFilter;
import com.mycompany.cevent.web.filter.StaticResourcesProductionFilter;
import com.mycompany.cevent.web.filter.gzip.GZipServletFilter;
import com.mycompany.cevent.web.servlet.HealthCheckServlet;
import org.atmosphere.cache.UUIDBroadcasterCache;
import org.atmosphere.cpr.AtmosphereFramework;
import org.atmosphere.cpr.AtmosphereServlet;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.autoconfigure.AutoConfigureAfter;
import org.springframework.boot.context.embedded.ServletContextInitializer;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.env.Environment;
import org.springframework.util.ReflectionUtils;

import javax.inject.Inject;
import javax.servlet.*;
import java.lang.reflect.Field;
import java.util.Arrays;
import java.util.EnumSet;
import java.util.HashMap;
import java.util.Map;

/**
 * Configuration of web application with Servlet 3.0 APIs.
 */
@Configuration
@AutoConfigureAfter(CacheConfiguration.class)
public class WebConfigurer implements ServletContextInitializer {

    private final Logger log = LoggerFactory.getLogger(WebConfigurer.class);

    @Inject
    private Environment env;

    @Inject
    private MetricRegistry metricRegistry;

    @Inject
    private HealthCheckRegistry healthCheckRegistry;

    @Override
    public void onStartup(ServletContext servletContext) throws ServletException {
        log.info("Web application configuration, using profiles: {}", Arrays.toString(env.getActiveProfiles()));
        EnumSet<DispatcherType> disps = EnumSet.of(DispatcherType.REQUEST, DispatcherType.FORWARD, DispatcherType.ASYNC);

        initMetrics(servletContext, disps);
        initAtmosphereServlet(servletContext);
        if (env.acceptsProfiles(Constants.SPRING_PROFILE_PRODUCTION)) {
            initStaticResourcesProductionFilter(servletContext, disps);
            initCachingHttpHeadersFilter(servletContext, disps);
        }
        initGzipFilter(servletContext, disps);

        log.info("Web application fully configured");
    }

    /**
     * Initializes the GZip filter.
     */
    private void initGzipFilter(ServletContext servletContext, EnumSet<DispatcherType> disps) {
        log.debug("Registering GZip Filter");

        FilterRegistration.Dynamic compressingFilter = servletContext.addFilter("gzipFilter", new GZipServletFilter());
        Map<String, String> parameters = new HashMap<>();

        compressingFilter.setInitParameters(parameters);

        compressingFilter.addMappingForUrlPatterns(disps, true, "*.css");
        compressingFilter.addMappingForUrlPatterns(disps, true, "*.json");
        compressingFilter.addMappingForUrlPatterns(disps, true, "*.html");
        compressingFilter.addMappingForUrlPatterns(disps, true, "*.js");
        compressingFilter.addMappingForUrlPatterns(disps, true, "/app/rest/*");
        compressingFilter.addMappingForUrlPatterns(disps, true, "/metrics/*");

        compressingFilter.setAsyncSupported(true);
    }

    /**
     * Initializes the static resources production Filter.
     */
    private void initStaticResourcesProductionFilter(ServletContext servletContext,
                                                     EnumSet<DispatcherType> disps) {

        log.debug("Registering static resources production Filter");
        FilterRegistration.Dynamic staticResourcesProductionFilter =
                servletContext.addFilter("staticResourcesProductionFilter",
                        new StaticResourcesProductionFilter());

        staticResourcesProductionFilter.addMappingForUrlPatterns(disps, true, "/");
        staticResourcesProductionFilter.addMappingForUrlPatterns(disps, true, "/index.html");
        staticResourcesProductionFilter.addMappingForUrlPatterns(disps, true, "/images/*");
        staticResourcesProductionFilter.addMappingForUrlPatterns(disps, true, "/fonts/*");
        staticResourcesProductionFilter.addMappingForUrlPatterns(disps, true, "/scripts/*");
        staticResourcesProductionFilter.addMappingForUrlPatterns(disps, true, "/styles/*");
        staticResourcesProductionFilter.addMappingForUrlPatterns(disps, true, "/views/*");
        staticResourcesProductionFilter.setAsyncSupported(true);
    }

    /**
     * Initializes the cachig HTTP Headers Filter.
     */
    private void initCachingHttpHeadersFilter(ServletContext servletContext,
                                              EnumSet<DispatcherType> disps) {
        log.debug("Registering Cachig HTTP Headers Filter");
        FilterRegistration.Dynamic cachingHttpHeadersFilter =
                servletContext.addFilter("cachingHttpHeadersFilter",
                        new CachingHttpHeadersFilter());

        cachingHttpHeadersFilter.addMappingForUrlPatterns(disps, true, "/images/*");
        cachingHttpHeadersFilter.addMappingForUrlPatterns(disps, true, "/fonts/*");
        cachingHttpHeadersFilter.addMappingForUrlPatterns(disps, true, "/scripts/*");
        cachingHttpHeadersFilter.addMappingForUrlPatterns(disps, true, "/styles/*");
        cachingHttpHeadersFilter.setAsyncSupported(true);
    }

    /**
     * Initializes Metrics.
     */
    private void initMetrics(ServletContext servletContext, EnumSet<DispatcherType> disps) {
        log.debug("Initializing Metrics registries");
        servletContext.setAttribute(InstrumentedFilter.REGISTRY_ATTRIBUTE,
                metricRegistry);
        servletContext.setAttribute(MetricsServlet.METRICS_REGISTRY,
                metricRegistry);
        servletContext.setAttribute(HealthCheckServlet.HEALTH_CHECK_REGISTRY,
                healthCheckRegistry);

        log.debug("Registering Metrics Filter");
        FilterRegistration.Dynamic metricsFilter = servletContext.addFilter("webappMetricsFilter",
                new InstrumentedFilter());

        metricsFilter.addMappingForUrlPatterns(disps, true, "/*");
        metricsFilter.setAsyncSupported(true);

        log.debug("Registering Metrics Servlet");
        ServletRegistration.Dynamic metricsAdminServlet =
                servletContext.addServlet("metricsServlet", new MetricsServlet());

        metricsAdminServlet.addMapping("/metrics/metrics/*");
        metricsAdminServlet.setAsyncSupported(true);
        metricsAdminServlet.setLoadOnStartup(2);

        log.debug("Registering HealthCheck Servlet");
        ServletRegistration.Dynamic healthCheckServlet =
                servletContext.addServlet("healthCheckServlet", new HealthCheckServlet());

        healthCheckServlet.addMapping("/metrics/healthcheck/*");
        healthCheckServlet.setAsyncSupported(true);
        healthCheckServlet.setLoadOnStartup(2);
    }

    /**
     * Initializes Atmosphere.
     */
    private void initAtmosphereServlet(ServletContext servletContext) {
        log.debug("Registering Atmosphere Servlet");
        AtmosphereServlet servlet = new AtmosphereServlet();
        Field frameworkField = ReflectionUtils.findField(AtmosphereServlet.class, "framework");
        ReflectionUtils.makeAccessible(frameworkField);
        ReflectionUtils.setField(frameworkField, servlet, new NoAnalyticsAtmosphereFramework());
        ServletRegistration.Dynamic atmosphereServlet =
                servletContext.addServlet("atmosphereServlet", servlet);

        atmosphereServlet.setInitParameter("org.atmosphere.cpr.packages", "com.mycompany.myapp.web.websocket");
        atmosphereServlet.setInitParameter("org.atmosphere.cpr.broadcasterCacheClass", UUIDBroadcasterCache.class.getName());
        atmosphereServlet.setInitParameter("org.atmosphere.cpr.broadcaster.shareableThreadPool", "true");
        atmosphereServlet.setInitParameter("org.atmosphere.cpr.broadcaster.maxProcessingThreads", "10");
        atmosphereServlet.setInitParameter("org.atmosphere.cpr.broadcaster.maxAsyncWriteThreads", "10");

        atmosphereServlet.addMapping("/websocket/*");
        atmosphereServlet.setLoadOnStartup(3);
        atmosphereServlet.setAsyncSupported(true);
    }

    /**
     * Atmosphere sends tracking data to Google Analytics, which is a potential security issue.
     * <p>
     * If you want to send this data, please use directly the AtmosphereFramework class.
     * </p>
     */
    public class NoAnalyticsAtmosphereFramework extends AtmosphereFramework {

        public NoAnalyticsAtmosphereFramework() {
            super();
        }

        @Override
        protected void analytics() {
            // noop
        }
    }
}