DropWizardApplicationRunner (run applications in-process)

DropWizardApplicationRunner.java

import io.dropwizard.Application;
import io.dropwizard.Configuration;
import io.dropwizard.cli.ServerCommand;
import io.dropwizard.configuration.ConfigurationFactory;
import io.dropwizard.setup.Bootstrap;
import io.dropwizard.setup.Environment;

import org.eclipse.jetty.server.Server;
import org.eclipse.jetty.util.component.AbstractLifeCycle;
import org.eclipse.jetty.util.component.LifeCycle;

import java.io.File;

/**
 * A utility to run DropWizard (http://dropwizard.io/) applications in-process.
 */
public class DropWizardApplicationRunner
{
  /**
   * Creates a Jetty server for an application that can be started / stopped in-process
   *
   * @param config
   *  An application configuration instance (with properties set)
   * @param applicationClass
   *  The {@link io.dropwizard.Application} implementation class
   * @param <T>
   *  The configuration class
   * @return
   *  A Jetty server
   */
  @SuppressWarnings("unchecked")
  public static <T extends Configuration>
  Server createServer(T config, Class<? extends Application<T>> applicationClass) throws Exception
  {
    // Create application
    final Application<T> application = applicationClass.getConstructor().newInstance();

    // Create bootstrap
    final ServerCommand<T> serverCommand = new ServerCommand<T>(application);
    final Bootstrap<T> bootstrap = new Bootstrap<T>(application);
    bootstrap.addCommand(serverCommand);
    application.initialize(bootstrap);

    // Write a temporary config file
    File tmpConfigFile = new File(
            System.getProperty("java.io.tmpdir"),
            config.getClass().getCanonicalName() + "_" + System.currentTimeMillis());
    tmpConfigFile.deleteOnExit();
    bootstrap.getObjectMapper().writeValue(tmpConfigFile, config);

    // Parse configuration
    ConfigurationFactory<T> configurationFactory
            = bootstrap.getConfigurationFactoryFactory()
                       .create((Class<T>) config.getClass(),
                               bootstrap.getValidatorFactory().getValidator(),
                               bootstrap.getObjectMapper(),
                               "dw");
    final T builtConfig = configurationFactory.build(
            bootstrap.getConfigurationSourceProvider(), tmpConfigFile.getAbsolutePath());

    // Configure logging
    builtConfig.getLoggingFactory()
               .configure(bootstrap.getMetricRegistry(),
                          bootstrap.getApplication().getName());

    // Environment
    final Environment environment = new Environment(bootstrap.getApplication().getName(),
                                                    bootstrap.getObjectMapper(),
                                                    bootstrap.getValidatorFactory().getValidator(),
                                                    bootstrap.getMetricRegistry(),
                                                    bootstrap.getClassLoader());

    // Initialize environment
    builtConfig.getMetricsFactory().configure(environment.lifecycle(), bootstrap.getMetricRegistry());
    bootstrap.run(builtConfig, environment);
    application.run(builtConfig, environment);

    // Server
    final Server server = builtConfig.getServerFactory().build(environment);
    server.addLifeCycleListener(new AbstractLifeCycle.AbstractLifeCycleListener()
    {
      @Override
      public void lifeCycleStopped(LifeCycle event)
      {
        builtConfig.getLoggingFactory().stop();
      }
    });

    return server;
  }
}