Dropwizard straddles the line between being a library and a framework. Its goal is to provide performant, reliable implementations of everything a production-ready web application needs. Because this functionality is extracted into a reusable library, your application remains lean and focused, reducing both time-to-market and maintenance burdens.
Jetty for HTTP: Because you can’t be a web application without HTTP, Dropwizard uses the Jetty HTTP library to embed an incredibly tuned HTTP server directly into your project. Instead of handing your application off to a complicated application server, Dropwizard projects have a main method which spins up an HTTP server. Running your application as a simple process eliminates a number of unsavory aspects of Java in production (no PermGen issues, no application server configuration and maintenance, no arcane deployment tools, no class loader troubles, no hidden application logs, no trying to tune a single garbage collector to work with multiple application workloads) and allows you to use all of the existing Unix process management tools instead.
Jersey for REST: For building RESTful web applications, we’ve found nothing beats Jersey (the JAX-RS reference implementation) in terms of features or performance. It allows you to write clean, testable classes which gracefully map HTTP requests to simple Java objects. It supports streaming output, matrix URI parameters, conditional GET requests, and much, much more.
Jackson for JSON: In terms of data formats, JSON has become the web’s lingua franca, and Jackson is the king of JSON on the JVM. In addition to being lightning fast, it has a sophisticated object mapper, allowing you to export your domain models directly.
Metrics for metrics: The Metrics library rounds things out, providing you with unparalleled insight into your code’s behavior in your production environment.
And Friends: In addition to Jetty, Jersey, and Jackson, Dropwizard also includes a number of libraries to help you ship more quickly and with fewer regrets.
Now that you’ve gotten the lay of the land, let’s dig in!
package com.example.helloworld;
import com.fasterxml.jackson.annotation.JsonProperty;
import io.dropwizard.core.Configuration;
import jakarta.validation.constraints.NotEmpty;
public class HelloWorldConfiguration extends Configuration {
@NotEmpty
private String template;
@NotEmpty
private String defaultName = "Stranger";
@JsonProperty
public String getTemplate() {
return template;
}
@JsonProperty
public void setTemplate(String template) {
this.template = template;
}
@JsonProperty
public String getDefaultName() {
return defaultName;
}
@JsonProperty
public void setDefaultName(String name) {
this.defaultName = name;
}
}
package com.example.helloworld;
import io.dropwizard.core.Application;
import io.dropwizard.core.setup.Bootstrap;
import io.dropwizard.core.setup.Environment;
public class HelloWorldApplicationStart extends Application<HelloWorldConfiguration> {
public static void main(String[] args) throws Exception {
new HelloWorldApplicationStart().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) {
// nothing to do yet
}
}
For
{
"id": 1,
"content": "Hi!"
}
we build
package com.example.helloworld.api;
import com.fasterxml.jackson.annotation.JsonProperty;
public class Saying {
private long id;
private String content;
public Saying() {
// Jackson deserialization
}
public Saying(long id, String content) {
this.id = id;
this.content = content;
}
@JsonProperty
public long getId() {
return id;
}
@JsonProperty
public String getContent() {
return content;
}
}
package com.example.helloworld.resources;
import com.codahale.metrics.annotation.Timed;
import com.example.helloworld.api.Saying;
import jakarta.ws.rs.GET;
import jakarta.ws.rs.Path;
import jakarta.ws.rs.Produces;
import jakarta.ws.rs.QueryParam;
import jakarta.ws.rs.core.MediaType;
import java.util.Optional;
import java.util.concurrent.atomic.AtomicLong;
@Path("/hello-world")
@Produces(MediaType.APPLICATION_JSON)
public class HelloWorldResource {
private final String template;
private final String defaultName;
private final AtomicLong counter;
public HelloWorldResource(String template, String defaultName) {
this.template = template;
this.defaultName = defaultName;
this.counter = new AtomicLong();
}
@GET
@Timed
public Saying sayHello(@QueryParam("name") Optional<String> name) {
final String value = String.format(template, name.orElse(defaultName));
return new Saying(counter.incrementAndGet(), value);
}
}
HelloWorldResource resource = new HelloWorldResource(
configuration.getTemplate(),
configuration.getDefaultName()
);
environment.jersey().register(resource);
package com.example.helloworld.health;
import com.codahale.metrics.health.HealthCheck;
public class TemplateHealthCheck extends HealthCheck {
private final String template;
public TemplateHealthCheck(String template) {
this.template = template;
}
@Override
protected Result check() throws Exception {
final String saying = String.format(template, "TEST");
if (!saying.contains("TEST")) {
return Result.unhealthy("template doesn't include a name");
}
return Result.healthy();
}
}
TemplateHealthCheck healthCheck = new TemplateHealthCheck(configuration.getTemplate());
environment.healthChecks().register("template", healthCheck);
Last modified 16 December 2024