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Base functionality for leanIX dropwizard-based services
There is a newer version: 2.0.10
package net.leanix.dropkit;

import net.leanix.dropkit.swagger.ApiDocsAssetServlet;

import com.codahale.metrics.MetricFilter;
import com.fasterxml.jackson.databind.util.ISO8601DateFormat;
import com.fasterxml.jackson.datatype.joda.JodaModule;
import com.google.common.base.Charsets;
import com.palominolabs.metrics.newrelic.AllEnabledMetricAttributeFilter;
import com.palominolabs.metrics.newrelic.NewRelicReporter;
import io.dropwizard.Configuration;
import io.dropwizard.assets.AssetsBundle;
import io.dropwizard.configuration.EnvironmentVariableSubstitutor;
import io.dropwizard.configuration.SubstitutingSourceProvider;
import io.dropwizard.setup.Bootstrap;
import io.dropwizard.setup.Environment;
import org.eclipse.jetty.servlets.CrossOriginFilter;

import java.util.EnumSet;
import java.util.concurrent.TimeUnit;

import javax.servlet.DispatcherType;
import javax.servlet.FilterRegistration;

/**
 * Application initialisation helper.
 *
 */
public class AppHelper {

    /**
     * Inits the use of iso8501 time format.
     *
     * @param bootstrap
     */
    public void initializeISO8601(Bootstrap bootstrap) {
        bootstrap.getObjectMapper().registerModule(new JodaModule());
        bootstrap.getObjectMapper().setDateFormat(new ISO8601DateFormat());
    }
    
    public void initialize(Bootstrap bootstrap) {
        // Enable variable substitution with environment variables
        bootstrap.setConfigurationSourceProvider(
                new SubstitutingSourceProvider(
                    bootstrap.getConfigurationSourceProvider(),
                    new EnvironmentVariableSubstitutor(false)));
        this.initializeISO8601(bootstrap);
    }
    
    /**
     * To be included in App.run() method
     * @param config
     * @param environment 
     */
    public void run(Configuration config, Environment environment) {
        this.addCORSFilter(environment);
        this.registerExceptionMappers(environment);
        this.registerNewRelicReporter(environment);
    }

    /**
     * To be included in App.run() method for serving swagger.json and swagger UI.
     * @param config
     * @param environment
     */
    public void runSwagger(Configuration config, Environment environment) {
        // add the servlet for static swagger UI assets (need to put leanix-swagger-ui into the classpath)
        new AssetsBundle("/swagger", "/docs", "index.html", "swagger").run(environment);

        // add the servlet serving the swagger definitions file (swagger.json)
        // swagger.json must be generated at service build time (with kong chen plugin)

        environment.servlets().addServlet(
                "api-docs",
                new ApiDocsAssetServlet("/swagger-assets", "/api-docs", "swagger.json", Charsets.UTF_8, "configureMeIfNeeded")
        ).addMapping("/api-docs/*");
    }

    /**
     * Registers mappers for invalid-entity and business logic exception.
     *
     *
     * @param environment
     */
    public void registerExceptionMappers(Environment environment) {
        //exception mappers
        environment.jersey().register(new InvalidEntityMapper());
        environment.jersey().register(new BusinessLogicExceptionMapper());
    }
    
    /**
     * Registers new relic reporter
     * @param environment 
     */
    public void registerNewRelicReporter(Environment environment)
    {
        NewRelicReporter reporter = new NewRelicReporter(
                environment.metrics(), 
                "NewRelic reporter", 
                MetricFilter.ALL,
                new AllEnabledMetricAttributeFilter(),
                TimeUnit.SECONDS,
                TimeUnit.MILLISECONDS,
                ""
        );
        reporter.start(1, TimeUnit.MINUTES);
    }

    /**
     * Enables cross-origin requests.
     *
     *
     * @param environment
     */
    public void addCORSFilter(Environment environment) {
        FilterRegistration.Dynamic filter = environment.servlets().addFilter("CORS", CrossOriginFilter.class);
        filter.addMappingForUrlPatterns(EnumSet.allOf(DispatcherType.class), true, "/*");
        filter.setInitParameter(CrossOriginFilter.ALLOWED_ORIGINS_PARAM, "*");
        filter.setInitParameter(CrossOriginFilter.ACCESS_CONTROL_ALLOW_ORIGIN_HEADER, "*");
        filter.setInitParameter(CrossOriginFilter.ALLOWED_HEADERS_PARAM, "accept,accept-encoding,accept-language,access-control-request-headers,access-control-request-method,api-key,authorization,cache-control,content-type,content-length,connection,host,pragma,referer,x-requested-with,origin,x-api-sync-mode,x-api-key,x-credentials");
        filter.setInitParameter(CrossOriginFilter.ALLOWED_METHODS_PARAM, "GET,PUT,POST,DELETE,OPTIONS");
        filter.setInitParameter(CrossOriginFilter.PREFLIGHT_MAX_AGE_PARAM, "5184000"); // 2 months
        filter.setInitParameter(CrossOriginFilter.ALLOW_CREDENTIALS_PARAM, "true");
    }
}