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Extensions¶

Extensions mechanism supposed to be used in guicey for all dropwizard specific features registration (instead of manual registrations).

All extensions are recognized and installed with appropriate installer. This page supposed to reference declaration examples of most common extensions. See installers section for details.

Warning

Extension is recognized only by one installer (according to installers order), even if it contains multiple signs! See installers report for installers order.

Declaration sources:

Tip

More installers (and so supported extensions types) could be available due to installed extension bundles. Use installers report to see all available installers.

Some extensins support order declaration with @Order() - see report.

Note

If you have problems with injection inside extensions (NPE errors) first check that you did not register extension manually!
It is a quite often mistake (especially with jersey extensions):

environment.jersey().register(new MyResource())

This way MyResource will not be managed by guice and so injections inside it will not work

Use constructor injection to prevent such errors (manual places will reveal immediately):

@Path("/")
public class MyResource {
    private final MyService service;

    @Inject
    public MyResource(MyService service) {
        this.service = service;
    }
}

Resource¶

@Path("/res")
@Produces('application/json')   
@Singleton
class SampleResource {

    @Inject
    private MyService service;

    @GET
    @Path("/sample")
    public Response sample() {
        return Response.ok(service.result()).build();
    }
}

Recognized by @Path annotation on class or implemented interface.

Task¶

@Singleton
public class MyTask extends Task {

    @Inject
    private MyService service;

    public TruncateDatabaseTask() {
        super("mytask");
    }

    @Override
    public void execute(ImmutableMultimap<String, String> parameters, PrintWriter output) throws Exception {
        service.doSomething();
    }
}

Recognized by base Task class.

Managed¶

@Singleton
public class MyService implements Managed {

    @Override
    public void start() throws Exception {
        ...
    }

    @Override
    public void stop() throws Exception {
        ...
    }
}

Recognized by Managed base class.

Health check¶

@Singleton
public class MyHealthCheck extends NamedHealthCheck {

    @Inject
    private MyService service;

    @Override
    protected Result check() throws Exception {
        if (service.isOk()) {
            return Result.healthy();
        } else {
            return Result.unhealthy("Service is not ok");
        }
    }

    @Override
    public String getName() {
        return "my-service";
    }
}

Recognized by base NamedHealthCheck class. Custom guicey base class used because it would be impossible to automatically register health check without name.

Jersey extensions¶

All jersey extensions are recognized by javax.ws.rs.ext.Provider jersey annotation. There are many extensions supported.

@Provider
@Singleton
public class DummyExceptionMapper implements ExceptionMapper<RuntimeException> {

    private final Logger logger = LoggerFactory.getLogger(DummyExceptionMapper.class);

    @Override
    public Response toResponse(RuntimeException e) {
        logger.debug("Problem while executing", e);
        return Response.status(Response.Status.BAD_REQUEST)
                .type(MediaType.TEXT_PLAIN)
                .entity(e.getMessage())
                .build();
    }

}

or

@Provider       
@Singleton
public class MyContainerRequestFilter implements ContainerRequestFilter {

    @Override
    public void filter(ContainerRequestContext requestContext) throws IOException {
    }
}

Eager singleton¶

@EagerSingleton
public class MyService {}

Recognized by @EagerSingleton annotation. Replacement of manual bind(MyService.class).asEagerSingleton().

More¶

This was only subset of supported extensions - see installers section.

You can add additional extensions support with a custom installer.