Initializes a Dropwizard Service health checks, resources, tasks, etc. using Spring @component annotations.

SpringServiceInitializer.java

package com.segmint.postdelivery.spring;

import java.util.Map;

import javax.ws.rs.Path;
import javax.ws.rs.ext.Provider;

import org.springframework.web.context.ContextLoaderListener;
import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;

import com.yammer.dropwizard.config.Configuration;
import com.yammer.dropwizard.config.Environment;
import com.yammer.dropwizard.tasks.Task;
import com.yammer.metrics.core.HealthCheck;

public class SpringServiceInitializer {

	/**
	 * Annotate your health checks, resources, tasks, etc. w/
	 * org.springframework.stereotype.Component to auto-inject them in to
	 * Spring, which will then add them to DropWizard env.
	 * 
	 * Preferred over Environment.scanPackagesForResourcesAndProviders since it
	 * makes prototypes, not singletons.
	 * 
	 * @param configuration
	 * @param environment
	 * @param basePackages
	 */
	public static void initialize(Configuration configuration, Environment environment, String... basePackages) {
		AnnotationConfigWebApplicationContext parent = new AnnotationConfigWebApplicationContext();
		AnnotationConfigWebApplicationContext ctx = new AnnotationConfigWebApplicationContext();

		parent.refresh();
		parent.getBeanFactory().registerSingleton("configuration", configuration);
		parent.registerShutdownHook();
		parent.start();

		// the real main app context has a link to the parent context
		ctx.setParent(parent);
		// let annotation scanning do its magic
		ctx.scan(basePackages);
		ctx.refresh();
		ctx.registerShutdownHook();
		ctx.start();

		// now that Spring is started, let's get all the beans that matter into
		// DropWizard

		Map<String, HealthCheck> healthChecks = ctx.getBeansOfType(HealthCheck.class);
		for (Map.Entry<String, HealthCheck> entry : healthChecks.entrySet()) {
			environment.addHealthCheck(entry.getValue());
		}

		Map<String, Object> resources = ctx.getBeansWithAnnotation(Path.class);
		for (Map.Entry<String, Object> entry : resources.entrySet()) {
			environment.addResource(entry.getValue());
		}

		Map<String, Task> tasks = ctx.getBeansOfType(Task.class);
		for (Map.Entry<String, Task> entry : tasks.entrySet()) {
			environment.addTask(entry.getValue());
		}

		Map<String, Object> providers = ctx.getBeansWithAnnotation(Provider.class);
		for (Map.Entry<String, Object> entry : providers.entrySet()) {
			environment.addProvider(entry.getValue());
		}

		// link Spring to the embedded Jetty in Dropwizard
		environment.addServletListeners(new ContextLoaderListener(ctx));
	}

}