Main.java

package jmodern;

import com.codahale.metrics.*;
import com.codahale.metrics.annotation.*;
import com.fasterxml.jackson.annotation.*;
import com.google.common.base.Optional;
import dagger.Module;
import dagger.ObjectGraph;
import dagger.Provides;
import io.dropwizard.Application;
import io.dropwizard.*;
import io.dropwizard.db.*;
import io.dropwizard.setup.*;
import java.util.concurrent.ThreadLocalRandom;
import java.util.concurrent.atomic.AtomicLong;
import javax.inject.Inject;
import javax.inject.Named;
import javax.validation.Valid;
import javax.validation.constraints.NotNull;
import javax.ws.rs.*;
import javax.ws.rs.core.*;
import org.hibernate.validator.constraints.*;

public class Main extends Application<Main.JModernConfiguration> {
    public static void main(String[] args) throws Exception {
        new Main().run(new String[]{"server", System.getProperty("dropwizard.config")});
    }
    
    @Override
    public void initialize(Bootstrap<JModernConfiguration> bootstrap) {
    }

    @Override
    public void run(JModernConfiguration cfg, Environment env) throws ClassNotFoundException {
        JmxReporter.forRegistry(env.metrics()).build().start(); // Manually add JMX reporting (Dropwizard regression)
        
        ObjectGraph objectGraph = ObjectGraph.create(new ModernModule(cfg));
        env.jersey().register(objectGraph.get(HelloWorldResource.class));
    }

    // YAML Configuration
    public static class JModernConfiguration extends Configuration {
        @JsonProperty private @NotEmpty String template;
        @JsonProperty private @NotEmpty String defaultName;
        @Valid @NotNull @JsonProperty private DataSourceFactory database = new DataSourceFactory();

        public DataSourceFactory getDataSourceFactory() { return database; }
        public String getTemplate()    { return template; }
        public String getDefaultName() { return defaultName; }
    }
    
    @Module(injects = HelloWorldResource.class)
    class ModernModule {
        private final JModernConfiguration cfg;

        public ModernModule(JModernConfiguration cfg) {
            this.cfg = cfg;
        }

        @Provides @Named("template") String provideTemplate() {
            return cfg.getTemplate();
        }

        @Provides @Named("defaultName") String provideDefaultName() {
            return cfg.getDefaultName();
        }
    }
    
    @Path("/hello-world")
    @Produces(MediaType.APPLICATION_JSON)
    public static class HelloWorldResource {
        private final AtomicLong counter = new AtomicLong();
        @Inject @Named("template") String template;
        @Inject @Named("defaultName") String defaultName;

        HelloWorldResource() {
        }

        @Timed // monitor timing of this service with Metrics
        @GET
        public Saying sayHello(@QueryParam("name") Optional<String> name) throws InterruptedException {
            final String value = String.format(template, name.or(defaultName));
            Thread.sleep(ThreadLocalRandom.current().nextInt(10, 500));
            return new Saying(counter.incrementAndGet(), value);
        }
    }
    
    // JSON (immutable!) payload
    public static class Saying {
        private long id;
        private @Length(max = 10) String content;

        public Saying(long id, String content) {
            this.id = id;
            this.content = content;
        }

        public Saying() {} // required for deserialization

        @JsonProperty public long getId() { return id; }
        @JsonProperty public String getContent() { return content; }
    }
}