Integrating Guice into Dropwizard

[Gili T.]

Hi,

There are serious problems integrating Guice into Dropwizard. I will start off by sharing what worked for me:

public class Main extends Service<Configuration>

{

public static void main(String[] args) throws Exception

{

new Main().run(args);

}

@Override

protected void initialize(Configuration configuration, Environment environment)

throws Exception

{

environment.addServletListeners(new JerseyContextListener());

// WORKAROUND: https://bugs.eclipse.org/bugs/show_bug.cgi?id=393738

environment.addServlet(NotFoundServlet.class, configuration.getHttpConfiguration().

getRootPath());

environment.addFilter(GuiceFilter.class, configuration.getHttpConfiguration().getRootPath());

}

@Override

public ServletContainer getJerseyContainer(DropwizardResourceConfig resourceConfig,

Configuration serviceConfig)

{

return null;

}

}

/**

 * A servlet that returns HTTP 404 for all methods.

 */

public class NotFoundServlet implements Servlet

{

private ServletConfig config;

@Override

public void init(ServletConfig config) throws ServletException

{

this.config = config;

}

@Override

public ServletConfig getServletConfig()

{

return config;

}

@Override

public void service(ServletRequest req, ServletResponse res)

throws ServletException, IOException

{

HttpServletRequest request;

HttpServletResponse response;

try

{

request = (HttpServletRequest) req;

response = (HttpServletResponse) res;

}

catch (ClassCastException e)

{

throw new ServletException("non-HTTP request or response");

}

response.sendError(404);

}

@Override

public String getServletInfo()

{

return getClass().getName();

}

@Override

public void destroy()

{

}

}

public class JerseyContextListener extends GuiceServletContextListener

{

private Injector injector;

@Override

protected Injector getInjector()

{

return Guice.createInjector(new JerseyModule());

}

}

public class JerseyModule extends JerseyServletModule

{

@Override

protected void configureServlets()

{

Map<String, String> params = new HashMap<>(10);

params.put(JSONConfiguration.FEATURE_POJO_MAPPING, "true");

params.put(PackagesResourceConfig.PROPERTY_PACKAGES, JerseyModule.class.getPackage().

getName());

params.put(ServletContainer.PROPERTY_WEB_PAGE_CONTENT_REGEX, "/(images|css|js)/.*");

params.put(ResourceConfig.PROPERTY_CONTAINER_REQUEST_FILTERS,

CachedEntityFilter.class.getName());

filter("/*").through(GuiceContainer.class, params);

}

}

The problem with the above code, although it works, is that you cannot configure ResourceConfig using Dropwizard and pass it into GuiceContainer. Instead, we are forced to pass filter parameters into GuiceContainer and totally disregarding Dropwizard's configuration. We lose type-safety and Dropwizard's nice API in the process.

The point of this discussion thread is to brainstorm on possible solutions. And with that, I turn the table to you :)

Thanks,

Gili

[Coda Hale]

I'd strongly suggest checking out 0.6.0-SNAPSHOT before continuing further. It moves the JerseyContainer to Environment, among other things.

---
Coda Hale
http://codahale.com

[cowwoc]

    I'll check it out, but the problem remains that GuiceContainer doesn't allow passing ResourceConfig to its (ServletContainer) superclass.

    If I understand correctly:

• There are two ways to configure the ResourceConfig used by ServletContainer.
• Either pass an instance to ServletContainer's constructor, or
• Update an existing ResourceConfig using the filter parameters (ServletContainer is a filter)
• Dropwizard would like to use the first mechanism (pass ResourceConfig to ServletContainer's constructor) and I favor this approach as well because it is type-safe (filter parameters are String-based) and offers a cleaner API.
• GuiceContainer only offers the second mechanism. It's easy to understand why: Guice can't mix @Injected and user-supplied arguments.

    I am aware of the following options, but there are obviously others:

• Use Filter init parameters when using Guice. Use Dropwizard's API when not using Guice. I dislike this approach because it isn't consistent.
• Find a way to @Inject ResourceConfig, have GuiceContainer's constructor to pass it to the superclass. I'm not sure how easy it is to do this (if at all possible).
• Create an alternative to ServletFilter, GuiceContainer. This is actually my favorite choice because of annoying bugs like http://code.google.com/p/google-guice/issues/detail?id=618 and http://code.google.com/p/google-guice/issues/detail?id=635
• In theory, all we'd need to do is invoke addFilter(new GuiceContainerReplacement(injector, resourceConfig)).
• GuiceContainerReplacement would bind Jersey to Guice's Injector, but its constructor would *not* be injected (as GuiceContainer is now). This would allow us to pass ResourceConfig up to the superclass as we would like.
  

    What do you think?

Gili

[Kim Betti]

Are (current) snapshots being published to any public Maven repository?

[Derek Stainer]

We're getting our snapshots from here: 

https://oss.sonatype.org/content/repositories/snapshots/

Derek

[Gili T.]

Eureka!

I managed to integrate Guice into Dropwizard 0.6.0-SNAPSHOT using the third approach.

• It turns out that you cannot drop ServletFilter because it's responsible for maintaining @RequestScope and other important things.
• It also turns out that JerseyServletModule requires GuiceContainer.class to be injectable. This means you cannot simply pass a singleton into JerseyServletModule.filter().
  

Here is what I did:

• JerseyServletModule remains unchanged
  
• Replace GuiceContainer(Injector) with three constructors that mirror and delegate to the ServletContainer constructors
• The private Injector field changes from "private final Injector injector" to "@Inject private Injector injector". In other words, we use property injection instead of constructor injection. I believe this is a lesser evil to the current situation.

That's it! Here is the updated GuiceContainer:

@Singleton

public class GuiceContainer extends ServletContainer {

    

    private static final long serialVersionUID = 1931878850157940335L;

    @Inject

    private Injector injector;

    private WebApplication webapp;

    public class ServletGuiceComponentProviderFactory extends GuiceComponentProviderFactory {

        public ServletGuiceComponentProviderFactory(ResourceConfig config, Injector injector) {

            super(config, injector);

        }

        

        @Override

        public Map<Scope, ComponentScope> createScopeMap() {

            Map<Scope, ComponentScope> m = super.createScopeMap();

            m.put(ServletScopes.REQUEST, ComponentScope.PerRequest);

            return m;

        }

    }

    /**

     * Creates a new container.

     */

    public GuiceContainer() {

    }

    /**

     * Creates a new container.

     *

     * @param app the JAX-RS application

     */

    public GuiceContainer(Application app) {

      super(app);

    }

    /**

     * Creates a new container.

     *

     * @param app the JAX-RS application

     */

    public GuiceContainer(Class<? extends Application> app) {

      super(app);

    }

    @Override

    protected ResourceConfig getDefaultResourceConfig(Map<String, Object> props,

            WebConfig webConfig) throws ServletException {

        return new DefaultResourceConfig();

    }

    @Override

    protected void initiate(ResourceConfig config, WebApplication webapp) {

        this.webapp = webapp;

        webapp.initiate(config, new ServletGuiceComponentProviderFactory(config, injector));

    }

    public WebApplication getWebApplication() {

        return webapp;

    }

}

Here is a sample application:

public class Main extends Service<Configuration>

{

public static void main(String[] args) throws Exception

{

new Main().run(args);

}

@Override

public void initialize(Bootstrap<Configuration> bootstrap)

{

}

@Override

public void run(Configuration configuration, Environment environment) throws Exception

{

                // Add resources using dropwizard. Horay!

environment.addResource(RootResource.class);

                // Pass the resourceConfig into GuiceContainer

GuiceContainer container = new GuiceContainer(environment.getJerseyResourceConfig());

environment.setJerseyServletContainer(container);

environment.addServletListeners(new JerseyContextListener(container, new UserModule()));

environment.addFilter(GuiceFilter.class, configuration.getHttpConfiguration().getRootPath());

}

}

public class JerseyContextListener extends GuiceServletContextListener

{

private final Injector injector;

public JerseyContextListener(GuiceContainer container, Module... modules)

{

this.injector = Guice.createInjector(Lists.asList(new JerseyModule(container), modules));

}

@Override

protected Injector getInjector()

{

return injector;

}

}

public class JerseyModule extends JerseyServletModule

{

private final GuiceContainer container;

/**

* Creates a new JerseyModule.

* <p/>

* @param container a container binding Jersey to Guice

*/

public JerseyModule(GuiceContainer container)

{

this.container = container;

}

@Override

protected void configureServlets()

{

bind(GuiceContainer.class).toInstance(container);

filter("/*").through(GuiceContainer.class);

}

}

[Gili T.]

I just made an interesting discovery. It turns out you don't need JerseyContextListener at all. It's sufficient for you to invoke:

  Guice.createInjector(Lists.asList(new JerseyModule(container), modules));

from within the Service. Doing so will cause Guice to invoke Injector.injectMembers(container) which will allow GuiceContainer to behave as expected when it gets an HTTP request. You don't need to do anything with the returned Injector.

As far as I can tell:

GuiceFilter starts/stops ServletScopes

ServletModule populates a Module with key/value pairs related to servlets, filters and their URIs (GuiceContainer is bound here)

I haven't yet figured out how GuiceFilter and ServletModule are linked to one another. I see GuiceFilter delegates to a filter pipeline but it's not clear how that pipeline is populated.

Gili

[David Morgantini]

This works really nicely for me.  The only thing I did was extract the service code into a bundle such that I could test the service run method without having to deal with the complexities of guice.

[Elias Torres]

Gili,

I almost have everything working. However, when I wanted to change my rootPath, I started getting 404s on requests that were working after following your instructions.

If I remove all of the guice-related glue, DW respects rootPath correctly in 0.6.0. I'm not sure if it helps, but I had Guice working with rootPath in 0.5.1.

This is all I added. Would you mind trying the same and see if it works for you? 

http:

  rootPath:  /v1/*

-Elias

[cowwoc]

    Sorry Elias. I no longer use DropWizard in my project. I plan on revisiting it in the future...

Good luck,
Gili

[GG]

If it helps others, dropwizard-guice package worked well for my team's needs and is available in maven central:  https://github.com/jaredstehler/dropwizard-guice

[cowwoc]

    I think it's important to clarify what dropwizard-guice doesn't do. It doesn't integrate GuiceFilter with dropwizard, which means you cannot use @RequestScoped and other useful stuff.

Gili

[Tatu Saloranta]

I think it'd be great to have a wiki page for known DropWizard
extensions. I think this is a very good way to extend the platform
(sorry! can't resist using the term here, at risk of sounding
enterprise-y).
Ideally new integration pieces would live outside of core package,
whether within main project or not. This can speed up development and
progress a lot, while keeping core mean & lean.

-+ Tatu +-

[Elias Torres]

I have a pull request coming with my fixes. Hang tight Guicers!

Sent from my iPhone

[Elias Torres]

I have submitted a pull request to have a sub-module with Guice support.

https://github.com/codahale/dropwizard/pull/227

I also have a stand-alone example with fixes to Gili's code and making sure we do have the GuiceFilter enabled to support RequestScoped items. In the pull request you'll find a bundle that can be called during the initialize phase.

bootstrap.addBundle(new GuiceBundle<HelloWorldConfiguration>() {
  @Override
  protected Collection<? extends Module> configureModules(HelloWorldConfiguration configuration) {
    return Lists.newArrayList(new HelloWorldModule(configuration));
  }
});

-Elias

[Elias Torres]

I forgot to point to the stand-alone example.

https://github.com/eliast/dropwizard-guice-example

-Elias

[cowwoc]

    Very nice. Keep up the good work! :)

Gili

[Elias Torres]

Thanks Gili you did most of the work. ;-)

Just to keep everyone posted. Coda suggested we hosted the extension separately since Guice is not used at Yammer and I agreed it was a good idea.

You can find it at https://github.com/HubSpot/dropwizard-guice

I did borrow Jared Stehler's auto config suggestion and made it available optionally if anybody wants it.

My last improvement to the extension was to make sure we supported injection on all of Jersey's objects such as HttpRequestContext and so on with RequestScope.

-Elias

[S Ahmed]

Thanks!

I've only used spring before, where exactly are the key bits that are using guice and wiring up/injects of the implementation bits together.

[Elias Torres]

All of the binding happens within the modules. You'd bind a class/interface to an instance or provider and so on.

-Elias

[S Ahmed]

So say I have:

public interface UserSevice {

  User getUserById(int id);

   ...

}

public class UserServiceImpl implements UserService {

  @Inject

  private UserDao userDao

}

public class HelloWorldResource {

  @Inject

  private UserService userService;

}

So now I need to wireup:

UserDao => UserDaoImpl

UserService => UserServiceImpl

Where would I do this? Just create a Services Module that wires up all my services (UserService, SearchService, etc.) and add it to the initialize in HelloWorldService like:

.addModule(new HelloWorldModule())

.addModule(new ServicesModule())

Or am I looking at this wrong, the UserService should be a property of my configuration like getTemplate?

[Elias Torres]

Exactly. Inside your ServicesModule you'd bind:

public class ServicesModule extends AbstractModule {

public void configure() {

  binder().bind(UserDao.class).to(UserDaoImpl.class);

  binder().bind(UserService.class).to(UserServiceImpl.class);

}

}

Done.

[Panagiotis Partheniadis]

Hello!

I'm trying hard to get to the point using the dropwizard-guice extension but i have a simple problem with my DAO :

This is the code before the use of DI:

final DBI db = factory.build(environment, connectionsServiceConf.getDatabaseConfiguration(), "postgresql");

environment.addResource(new ConnectionResource(db.onDemand(ConnectionDAO.class));

So, my DAO implementation is the one returned from the db.OnDemand method. How im i supposed to inject this instance when the AbstractModule subclass is registered during the initialize phase (and before the run phase) where the DBI cannot be available? 

[Elias Torres]

Here's a gist explaining how I do it.

https://gist.github.com/4594778

You also don't have add the resources directly, since the scanner in dropwizard-guice will automatically pick it up. In general, I let Guice construct my resources so it manages all of the injection. You can still decide to have singleton or per-request resources via annotations.

-Elias

[Panagiotis Partheniadis]

Played nicely!

Thanks!

[Panagiotis Partheniadis]

Hello again,

I'm using the Guice AOP facilities in order to enable logging using a MessageInterceptor and a @Logged annotation. Is there a way to somehow have access to a Request Header that i need to log? 

[Elias Torres]

You have access to all of these properties found in JerseyServletModule.

http://jersey.java.net/nonav/apidocs/1.8/contribs/jersey-guice/com/sun/jersey/guice/JerseyServletModule.html

WebApplication

WebApplication

Providers

FeaturesAndProperties

MessageBodyWorkers

ExceptionMapperContext

HttpContext

UriInfo

ExtendedUriInfo

HttpRequestContext

HttpHeaders

Request

SecurityContext

HttpResponseContext

You just need to make sure you are in the right scope (RequestScope).

-Elias

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[Matt Veitas]

I came across this in GitHub:

https://github.com/axiak/dropwizard-guice

[Elias Torres]

Yes. I work with Mike Axiak at HubSpot. That's a fork of the dropwizard-guice we built for using dropwizard at our company.

Let me know if we can be of help.

-Elias

--

[Panagiotis Partheniadis]

Hello,

I have the following problem. I need to implement an Integration Test for my service. Essentially, i need to start my service and make some calls to it using my Client Access Library for this Service. The start and stop of the service is done using an EmbeddedServerCommand as mentioned in an other thread. I also use the Hubspot dropwizard-guice integration and everything works fine. Nevertheless, it is apparent that in order to call the Service using my Client Access Library, i need to have access to the Http Client configuration along with the Service Port. From that information, i can provide my Library with the HttpClient required to make a call. I know that i can use direct values but i would rather not, as all the relevant information are already loaded in Guice by your Bundle. I just need some kind of access to it. The EmbeddedServerCommand implementation can be found at https://gist.github.com/tcovo/4512416

Can you take a look please?

[andrew....@seekersolutions.com]

@Elias Torres: Am I missing something when trying to use your gist? I get a runtime error from configuresDBI(MyConfiguration, Environment) -- "Could not find a suitable constructor in com.yammer.dropwizard.config.Environment. Classes must have either one (and only one) constructor annotated with @Inject or a zero-argument constructor that is not private."