Develop RESTFul services using Dropwizard Java framework

This document will guide you through the process of creating a simple Dropwizard project: Hello World.

Overview:

Dropwizard is a Java framework for developing ops-friendly, high-performance, RESTful web services. This framework bundles with Jetty for http sever, Jersey for REST and Jackson for JSON mapping. It offers some additional few other additional features like Metrics.

Setting up Maven:

I recommend you use Maven for new Dropwizard applications. Current version of Dropwizard 0.8.1.

<dependency>

  <groupId>io.dropwizard</groupId>

  <artifactId>dropwizard-core</artifactId>

  <version>0.8.0</version>

</dependency>

Creating A Configuration Class

Each Dropwizard application has its own subclass of the Configuration class which specifies environment-specific parameters. These parameters are specified in a YAML configuration file which is deserialized to an instance of your application’s configuration class and validated

import io.dropwizard.Configuration;

public class HelloWorldConfiguration extends Configuration {

// Add your own configuration variables

}

Creating a Representation class:

This class will be look like Model class and it designed for generating the JSON response. Representation class will be look like below.

import com.fasterxml.jackson.annotation.JsonProperty;

import org.hibernate.validator.constraints.Length;

public class Saying {

    private long id;

    @Length(max = 3)

    private String content;

    public Saying() {

    }

    public Saying(long id, String content) {

        this.id = id;

        this.content = content;

    }

    @JsonProperty

    public long getId() {

        return id;

    }

    @JsonProperty

    public String getContent() {

        return content;

    }

}

Creating  Resource Class:

You need a resource which returns Saying instances from the URI /hello-world, so our resource class will look like this:

import javax.ws.rs.GET;

import javax.ws.rs.Path;

import javax.ws.rs.Produces;

import javax.ws.rs.QueryParam;

import javax.ws.rs.core.MediaType;

import model.Saying;

import java.util.concurrent.atomic.AtomicLong;

@Path("/hello-world")

@Produces(MediaType.APPLICATION_JSON)

public class HelloWorldResource {

    private final AtomicLong counter;

    public HelloWorldResource() {

        this.counter = new AtomicLong();

    }

    @GET

    public Saying sayHello(@QueryParam("name") String name) {

        final String value = name;

        return new Saying(counter.incrementAndGet(), value);

    }

}

Creating An Application Class

Application going to be the Main class for your application. It will register your resource class. It will be look like below.

import configuration.HelloWorldConfiguration;

import io.dropwizard.Application;

import io.dropwizard.setup.Bootstrap;

import io.dropwizard.setup.Environment;

import resources.HelloWorldResource;

public class HelloWorldApplication extends Application<HelloWorldConfiguration> {

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

        new HelloWorldApplication().run(args);

    }

    @Override

    public String getName() {

        return "hello-world";

    }

    @Override

    public void initialize(Bootstrap<HelloWorldConfiguration> bootstrap) {

        // nothing to do yet

    }

    @Override

    public void run(HelloWorldConfiguration configuration,

                    Environment environment) {

                final HelloWorldResource resource = new HelloWorldResource();

                environment.jersey().register(resource);

    }

}

Create a YMAL file and place it your resource folder. It will be look like below

server:

#  softNofileLimit: 1000

#  hardNofileLimit: 1000

  applicationConnectors:

    - type: http

      port: 8085

# this requires the alpn-boot library on the JVM's boot classpath

#    - type: spdy3

#      port: 8445

#      keyStorePath: example.keystore

#      keyStorePassword: example

#      validateCerts: false

  adminConnectors:

    - type: http

      port: 8086

Finally the run the Application class which will have main method from your eclipse and pass the below parameters to your main class.

server <YML_file_path>