Introduction to Dropwizard
What’s a Dropwizard?
Dropwizard is a Java framework for developing ops-friendly, high-performance, RESTful web services.
Dropwizard pulls together stable, mature libraries from the Java ecosystem into a simple, light-weight package that lets you focus on getting things done.
Dropwizard has out-of-the-box support for sophisticated configuration, application metrics, logging, operational tools, and much more, allowing you and your team to ship a production-quality web service in the shortest time possible.
Best-of-breed Java libraries
- Jetty for HTTP
- Web server, Servlet container
- Jersey for REST
- JAX-RS reference implementation
- Jackson for JSON
- Freemarker and Mustasche
- Authentication
- HTTP Basic Auth
- OAuth2
Best-of-breed Java libraries
More modules
http://modules.dropwizard.io- Official modules
- Discovery for Zookeeper
- Health check with Elasticsearch
- Flyway instead of Liquibase
- Google's Protocol Buffers
- Large list of 3rd party modules
Releases
Main components
- Configuration
- Application
- Representation
- Resource
- Health check
Configuration
- Defined in a YAML file - Example
- Configuration class - Example
- Configuration reference
Configuration file
YAML
#server configuration
server:
applicationConnectors:
- type: http
port: 8080
- type: https
port: 8443
keyStorePath: example.keystore
keyStorePassword: example
validateCerts: false
validatePeers: false
fancyCoolProperty: Look at me I am cool and fancy
# Database settings.
database:
# the name of your JDBC driver
driverClass: org.h2.Driver
# the username
user: sa
# the password
password: sa
# the JDBC URL
url: jdbc:h2:./target/example
Configuration class
Java
public class ApplicationConfiguration extends Configuration {
@NotEmpty
private String fancyCoolProperty;
@JsonProperty
public String getFancyCoolProperty() {
return fancyCoolProperty;
}
@JsonProperty
public void setFancyCoolProperty(String fancyCoolProperty) {
this.fancyCoolProperty = fancyCoolProperty;
}
}
Application
- Application class - Example
Application class
public class HelloWorldApplication extends Application<ApplicationConfiguration> {
@Override
public String getName() {
return "hello-world";
}
@Override
public void initialize(Bootstrap<ApplicationConfiguration> bootstrap) {
// nothing to do yet
}
@Override
public void run(ApplicationConfiguration configuration, Environment environment) {
// nothing to do yet
}
}
Representation
- Jackson (JSON) annotated POJO - Example
- Should be immutable
Representation
public class Saying {
private String content;
public Saying() {
// Jackson deserialization
}
public Saying(String content) {
this.content = content;
}
@JsonProperty
public String getContent() {
return content;
}
}
Resource
- The meat-and-potatoes of Dropwizard
- JAX-RS API (Jersey)
Resource
@Path("/hello-world")
@Produces(MediaType.APPLICATION_JSON)
public class HelloWorldResource {
@GET
public Saying sayHello(@QueryParam("name") Optional<String> name) {
final String value = name.orElse("unkown");
return new Saying(value);
}
}
Registering a resource
public void run(ApplicationConfiguration configuration, Environment environment) {
final HelloWorldResource resource = new HelloWorldResource();
environment.jersey().register(resource);
}
Health check
Provided by Dropwizard Metrics
A health check is basically a small self-test which your application performs to verify that a specific component or responsibility is performing correctly.
Health check
public class SimpleHealthCheck extends HealthCheck {
@Override
protected Result check() throws Exception {
//check some stuff here!
return Result.healthy("Everything is fine");
}
}
Registering a health check
public void run(ApplicationConfiguration configuration, Environment environment) {
final SimpleHealthCheck healthCheck = new SimpleHealthCheck();
environment.healthChecks().register("simpleCheck", healthCheck);
}
Running your application
Do you remember the Java main() method?
public static void main(final String[] args) throws Exception {
final HelloWorldApplication application = new HelloWorldApplication();
application.run(args);
}
Running your application
- Within the IDE
- As Maven or Gradle task
- As self contained jar
- Make features not war (JAR not WAR)
- java -jar application.jar server application.yml
Dropwizard is used by
Some Competitors
Ratpack, Ninja framework, ...
Questions?
Legal information
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