Dropwizard HK2 Integration

This bundle binds and integrates Dropwizard's HealthCheck, Metric, MetricSet, LifeCycle, LifeCycle.Listener, and Managed objects with HK2, allowing these components to be registered directly with Jersey and fully injected with any other services also known to HK2. Additionally, it provides access to the Jersey ServiceLocator from the admin ServletContext, default bindings for many Dropwizard components such as the Validator, ObjectMapper, MetricRegistry, HealthCheckRegistry, your Application, your Configuration, the Environment and LifecycleEnvironment, as well as each bundle added to your application.

To use this bundle, add it to your application in the initialize method:

@Override
public void initialize(Bootstrap<YourConfig> bootstrap) {
    // This ensures there's only ever one HK2 bundle; don't use bootstrap.addBundle(new HK2Bundle<>());
    HK2Bundle.addTo(bootstrap);
}

Then, update your health checks, metrics, and managed components to use the custom Jersey component marker interfaces: InjectableHealthCheck, InjectableManaged, InjectableLifeCycle, InjectableLifeCycleListener, InjectableMetric, or InjectableMetricSet. These are necessary for Jersey to identify the components as a valid Jersey component, and just extend the Dropwizard interfaces of similar name. Here is an example health check:

@Named("TestHealthCheck")
public class TestInjectableHealthCheck extends InjectableHealthCheck {
    private final TestConfig config;

    @Inject
    public TestInjectableHealthCheck(TestConfig config) {
        this.config = config;
    }

    public TestConfig getConfig() {
        return config;
    }

    @Override
    protected Result check() throws Exception {
        return Result.healthy();
    }
}

Health checks and Metrics can also make use of the @Named() annotation to identify the name under which the component should be registered. If a name is not provided, a warning will be printed and a name generated in the format of ClassName.RandomUUID under which the component will be registered.

Lastly, register your components directly with Jersey:

@Override
public void run(TestConfig testConfig, Environment environment) throws Exception {
    environment.jersey().register(YourInjectableHealthCheck.class);
    environment.jersey().register(YourInjectableLifeCycle.class);
}

They will now be injected and registered properly with Dropwizard after HK2 and Jersey are initialized.

To access the ServiceLocator from the admin ServletContext, query the context attribute identified by HK2Bundle.SERVICE_LOCATOR:

ServiceLocator locator = (ServiceLocator) getServletConfig().getServletContext().getAttribute(HK2Bundle.SERVICE_LOCATOR);

RequestScoped bindings are unavailable in the admin context, but singletons and other scopes are available.