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Dropwizard & Spring The perfect Java REST stack

Jacek Furmankiewicz

Architect @ PROS, Inc.

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Dropwizard

What is it and why is it so exciting?

Dropwizard

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Dropwizard

Created by Coda Hale @ Yammer

http://dropwizard.io

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Dropwizard

Best-of-breed Java libraries integrated into one embedded application package

● Embedded Jetty (no WAR, no external servlet container)

● JAX-RS (Jersey) for REST APIs

● JSON (Jackson)

● Logging (Logback and SLF4J)

● Hibernate Validators

● Metrics (application SLA and performance)

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Dropwizard

Embedded Jetty● Restart your code in seconds. Run your code from the IDE.

● No WAR to recompile (ever!)

● No WAR to redeploy (ever!)

● No servlet container (Tomcat, Websphere, Weblogic, etc) to install

● Debug from your IDE (you have a main()), no need to attach to a separate process

● No need to share heap and GC issues with other apps running in the same servlet container

● Total process isolation (one misbehaving WAR (e.g. OutOfMemoryException) cannot bring down the entire server process)

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Dropwizard

Anatomy of a Dropwizard application

Jetty JerseyYOUR CODE(business logic, DAO, Spring, JPA, etc.)

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Dropwizard

Multiple apps on the same server

Jetty Jersey APP 1

pid 1843

Jetty Jersey APP 2

pid 1407

Jetty Jersey APP 3

pid 1976

Own JVM4 GB heap

Own JVM4 GB heap

Own JVM4 GB heap

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Dropwizard

Operations-friendly and ready for deployment

● Opens 2 HTTP ports: one for public APIs (i.e. your REST services), one for admin APIs (e.g. run GC, refresh internal caches, etc)

● Admin port can be closed off on the firewall and inaccessible to outside world

● Health Check APIs to allow easy monitoring from external tools like Nagios

● @Timed annotation on any single REST API allows to track its SLA using Metrics library

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Dropwizard

Ease of deployment● Dropwizard apps can be easily compiled into a single JAR with all dependencies

(e.g. using Maven Shade or Gradle Shadow plugins)

● Your entire app consists of two files:

YAML config fileJAR application file

● Trivial to run from command line:

java -server myapp.jar server myapp.yml

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Dropwizard

Ease of deployment – part 2

● Can be wrapped in an RPM or DEB to install on Linux clusters

● Can be registered as a Linux daemon, e.g.

sudo start myapp

sudo stop myapp

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Dropwizard

Embedding HTML resources

● Dropwizard provides the concept of AssetBundle, which allows to bundle HTML/JS/CSS assets directly in the app (via your src/main/resources folder)

● Perfect for creating a modern HTML5 Javascript UI (Backbone.js, Ember.js, Angular.js, etc) powered by rock-solid super fast Java REST APIs – the best of both worlds

● In 2013, you should not be using any Java (or .Net or Python or Ruby) server-side web frameworks.

HTML5 and Javascript have won and are the future of web development.

Java is best at providing REST APIs to power them with top reliability and performance.

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Dropwizard and Spring

Dropwizard and Spring DI

Adding dependency injection

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Dropwizard and Spring

Integrating Spring DI● Start up parent Spring context (AnnotationConfigWebApplicationContext)

● Inject Dropwizard Configuration object into it (so that it is available as a Spring bean)

● Start a child context (with the parent in it), also of type AnnotationConfigWebApplicationContext

● Extract all the Spring beans that Dropwizard cares about from the context and register them within Dropwizard:

– JAX-RS @Path resources and @Provider classes

– Dropwizard Task and HealthCheck objects

● Link Spring with the embedded Jetty instance, so that it behaves just as if it were running in a regular servlet container

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Dropwizard and Spring

Integrating Spring DI – part 2

Sample app with a full example:

https://github.com/jacek99/dropwizard-spring-di-security-onejar-example

In particular this class has all the low-level details:

MyAppService.java

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Dropwizard and Spring

Dropwizard and Spring Security

Adding enterprise-grade security

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Dropwizard and Spring Security

● @ImportResource Spring Security XML config file into your root Spring @Configuration class

● Activate Spring Security filter

● Provides both HTTP and method level (@Secured) support

● Present in github sample app covered previously

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Dropwizard

Dropwizard user comments

Words from people who use it every day

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Dropwizard

● Dropwizard is a godsend for all those of us who just need to get stuff DONE.

● Dropwizard changed the rules of the game completely. We have dramatically changed the way of working and increased the speed of whole development process. Dropwizard is being considered as a Restful Application Framework but this is totally unfair and limiting its potential. We have just added a few classes without forking it to operate Spring Framework and it is working wonderfully. That is to say, Dropwizard can be also considered as a "embedded application development framework" and we are using in this way

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Dropwizard

Q&A

PROSInterested in Big Data and real-time

challenges?We're hiring!

http://www.pros.com/company/working-pros/

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