WebConfigurer.java

package com.mycompany.myapp.config;

import com.codahale.metrics.MetricRegistry;
import com.codahale.metrics.servlet.InstrumentedFilter;
import com.codahale.metrics.servlets.MetricsServlet;
import com.mycompany.myapp.web.filter.CachingHttpHeadersFilter;
import com.mycompany.myapp.web.filter.StaticResourcesProductionFilter;
import com.mycompany.myapp.web.filter.gzip.GZipServletFilter;
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 javax.inject.Inject;
import javax.servlet.*;
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;

    @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);
        if (env.acceptsProfiles(Constants.SPRING_PROFILE_PRODUCTION)) {
            initStaticResourcesProductionFilter(servletContext, disps);
            initCachingHttpHeadersFilter(servletContext, disps);
        }
        initGzipFilter(servletContext, disps);
        if (env.acceptsProfiles(Constants.SPRING_PROFILE_DEVELOPMENT)) {
            initH2Console(servletContext);
        }

        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);

        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);
    }
    /**
     * Initializes H2 console
     */
    private void initH2Console(ServletContext servletContext) {
        log.debug("Initialize H2 console");
        ServletRegistration.Dynamic h2ConsoleServlet = servletContext.addServlet("H2Console", new org.h2.server.web.WebServlet());
        h2ConsoleServlet.addMapping("/console/*");
        h2ConsoleServlet.setLoadOnStartup(1);
    }


}