RESTful Groovy Options for building a Services Oriented Architecture in Groovy Kyle Boon 

Technical Lead @ Bloomhealth [email protected] @kyleboon http://www.kyleboon.org Kyle Boon 

Architecture 2011 

Architecture 2012 

Architecture 2013 

Goals Separate components Allow for different SLAs for each component Be able to combine components in different ways Increase developer productivity and ownership 

Complete Tool Chain Groovy Grails for web applications Dropwizard for JSON web services Gradle for builds Swagger for Service Discovery Spock for testing Gatling for Performace/Load Testing Redis for Caching RabbitMQ for messaging Chef for infrastructure 

What is Dropwizard Dropwizard is a heavily opinionated framework for building web services on the JVM. It is mostly glue around mature java libraries like Jetty, Jersey, Jackson and Guava. Dropwizard has out­of­the­box support for sophisticated configuration, application metrics, logging, operational tools, and much more, allowing you and your team to ship a production­quality HTTP+JSON web service in the shortest time possible. 

@coda As I've said before, the only reason Dropwizard exists at all is to provide opinions on what a service should be. It uses fat JARs because I think they work better. It embeds Jetty because I think that works better. It uses Jackson because I think that works better. It uses Jersey because I think that works better. It has a single YAML configuration file because I think that works better. It wraps Logback because I think that works better. Who Created it? 

How does it work? Deployed as a fat jar and starts jetty. No need for a container. Start the server from the command line by running: p u b l i c s t a t i c v o i d m a i n ( S t r i n g [ ] a r g s ) t h r o w s E x c e p t i o n { n e w C o n t a c t s S e r v i c e ( ) . r u n ( a r g s ) } j a v a - j a r c o n t a c t _ d r o p w i z a r d - s h a d o w - 0 . 1 . 0 - S N A P S H O T . j a r s e r v e r s t a r t d e v _ c o n f i g . y m l 

The Service Services are a collection of bundles, commands, healthchecks, tasks and resources. The service class defines all of the abilities of your application. @ O v e r r i d e p u b l i c v o i d i n i t i a l i z e ( B o o t s t r a p b o o t s t r a p ) { b o o t s t r a p . n a m e = ' c o n f i g u r a t i o n _ s e r v i c e ' b o o t s t r a p . a d d B u n d l e m i g r a t i o n s B u n d l e b o o t s t r a p . a d d B u n d l e h i b e r n a t e B u n d l e b o o t s t r a p . a d d B u n d l e ( n e w A s s e t s B u n d l e ( ' / s w a g g e r - u i - 1 . 1 . 0 / ' , ' / s w a g g e r ' ) ) b o o t s t r a p . a d d C o m m a n d ( n e w m i g r a t i o n s C o m m a n d ( ) ) } @ O v e r r i d e p u b l i c v o i d r u n ( C o n t a c t s C o n f i g u r a t i o n c o n f i g u r a t i o n , E n v i r o n m e n t e n v i r o n m e n t ) t h r o w s C l a s s N o t F o u n d E x c e p t i o n { C o n t a c t D A O c o n t a c t D A O = n e w C o n t a c t D A O ( h i b e r n a t e B u n d l e . s e s s i o n F a c t o r y ) e n v i r o n m e n t . a d d R e s o u r c e ( n e w C o n t a c t R e s o u r c e ( c o n t a c t D A O ) ) } 

The Resource Resources model what is exposed via your RESTful API. Dropwizard uses Jersey for this so these classes are mostly jersey annotations. @ P a t h ( ' / c o n t a c t s ' ) @ P r o d u c e s ( M e d i a T y p e . A P P L I C A T I O N _ J S O N ) c l a s s C o n t a c t R e s o u r c e { p r i v a t e f i n a l C o n t a c t D A O c o n t a c t D A O p u b l i c C o n t a c t R e s o u r c e ( C o n t a c t D A O c o n t a c t D A O ) { t h i s . c o n t a c t D A O = c o n t a c t D A O } @ T i m e d ( n a m e = ' c r e a t e C o n t a c t ' ) @ P O S T @ U n i t O f W o r k p u b l i c C o n t a c t c r e a t e C o n t a c t ( @ V a l i d C o n t a c t c o n t a c t ) { r e t u r n c o n t a c t D A O . s a v e O r U p d a t e ( c o n t a c t ) } } 

The Representation Your POGOs will be turned into JSON via Jackson. Hibernate Validator lets you specify validation rules. @ T o S t r i n g @ E q u a l s A n d H a s h C o d e c l a s s C o n t a c t { @ J s o n P r o p e r t y L o n g i d @ N o t N u l l @ N o t E m p t y @ J s o n P r o p e r t y S t r i n g f i r s t N a m e @ N o t N u l l @ N o t E m p t y @ J s o n P r o p e r t y S t r i n g l a s t N a m e @ T r a n s i e n t @ J s o n I g n o r e d e f s o m e C r a p = f a l s e } 

Metrics Yammer Metrics is built in and provides metrics over an administration port (8081). Resources can be annotated with @ T i m e d or @ M e t e r e d , and @ E x c e p t i o n M e t e r e d . " p o s t - r e q u e s t s " : { " t y p e " : " t i m e r " , " d u r a t i o n " : { " u n i t " : " m i l l i s e c o n d s " , " m i n " : 0 . 0 , " m a x " : 0 . 0 , " m e a n " : 0 . 0 , " s t d _ d e v " : 0 . 0 , " m e d i a n " : 0 . 0 , " p 7 5 " : 0 . 0 , " p 9 5 " : 0 . 0 , " p 9 8 " : 0 . 0 , " p 9 9 " : 0 . 0 , " p 9 9 9 " : 0 . 0 } , " r a t e " : { " u n i t " : " s e c o n d s " , " c o u n t " : 0 , " m e a n " : 0 . 0 , " m 1 " : 0 . 0 , " m 5 " : 0 . 0 , " m 1 5 " : 0 . 0 } } 

Health Checks Health Checks are a method to make sure the infrastructure your service depends on are all running. They are accessible on the administration port. p u b l i c c l a s s R e d i s H e a l t h C h e c k e x t e n d s H e a l t h C h e c k { p r i v a t e s t a t i c f i n a l S t r i n g E C H O = ' c h e c k i n g ' p r i v a t e f i n a l J e d i s P o o l j e d i s P o o l p u b l i c R e d i s H e a l t h C h e c k ( J e d i s P o o l j e d i s P o o l ) { s u p e r ( ' r e d i s ' ) t h i s . j e d i s P o o l = j e d i s P o o l } @ O v e r r i d e p r o t e c t e d R e s u l t c h e c k ( ) t h r o w s E x c e p t i o n { i f ( E C H O . e q u a l s I g n o r e C a s e ( j e d i s P o o l . r e s o u r c e . e c h o ( E C H O ) ) ) { r e t u r n R e s u l t . h e a l t h y ( ) } r e t u r n R e s u l t . u n h e a l t h y ( ' M a n a g e d J e d i s P o o l c o n n e c t i v i t y i s d o w n ! ' ) } } 

Bundles Bundles are reusable blocks of behaviour designed to be reused across services. Assets, Hibernate and Liquibase are all implemented as Dropwizard Bundles. @ S l f 4 j a b s t r a c t c l a s s R e d i s B u n d l e i m p l e m e n t s C o n f i g u r e d B u n d l e { M a n a g e d J e d i s P o o l j e d i s P o o l a b s t r a c t R e d i s C o n f i g u r a t i o n g e t R e d i s C o n f i g u r a t i o n ( T c o n f i g u r a t i o n ) @ O v e r r i d e p u b l i c f i n a l v o i d i n i t i a l i z e ( B o o t s t r a p b o o t s t r a p ) { l o g . i n f o ( ' I n i t i a l i z i n g R e d i s B u n d l e ' ) } @ O v e r r i d e p u b l i c f i n a l v o i d r u n ( T c o n f i g u r a t i o n , E n v i r o n m e n t e n v i r o n m e n t ) t h r o w s E x c e p t i o n { j e d i s P o o l = n e w M a n a g e d J e d i s P o o l ( n e w J e d i s P o o l C o n f i g ( ) , g e t R e d i s C o n f i g u r a t i o n ( c o n f i g u r a t i o n ) . h o s t , g e t R e d i s C o n f i g u r a t i o n ( c o n f i g u r a t i o n ) . p o r t , g e t R e d i s C o n f i g u r a t i o n ( c o n f i g u r a t i o n ) . t i m e o u t , g e t R e d i s C o n f i g u r a t i o n ( c o n f i g u r a t i o n ) . d b ) e n v i r o n m e n t . m a n a g e ( j e d i s P o o l ) e n v i r o n m e n t . a d d H e a l t h C h e c k ( n e w R e d i s H e a l t h C h e c k ( j e d i s P o o l ) ) } } 

Commands Commands add options to the command line interface of your service. For example the server starts based on the 'server' command. Migrations run based on the 'db migrate' command. You might add your own command for running functional tests or seeding the database. 

Tasks Tasks are run time actions available over the administration port. Dropwizard ships with a garbage collection task. You might want to right a task to clean a cache by key. c l a s s F l u s h R e d i s T a s k e x t e n d s T a s k { M a n a g e d J e d i s P o o l m a n a g e d J e d i s P o o l p r o t e c t e d F l u s h R e d i s T a s k ( S t r i n g n a m e , M a n a g e d J e d i s P o o l m a n a g e d J e d i s P o o l ) { s u p e r ( n a m e ) t h i s . m a n a g e d J e d i s P o o l = m a n a g e d J e d i s P o o l } @ O v e r r i d e v o i d e x e c u t e ( M a p p a r a m e t e r s , P r i n t W r i t e r o u t p u t ) t h r o w s E x c e p t i o n { J e d i s j e d i s = m a n a g e d J e d i s P o o l . r e s o u r c e j e d i s . f l u s h D B ( ) } } 

Other Stuff Configuration Logging Hibernate/JDBI Clients Authentication Views 

Grails 2.3 New REST APIs, making it easy to build REST APIs in Grails Scaffolding plugin that can generate REST controllers and Async controllers 

Declaring the resource as part of the domain p a c k a g e g r a i l s . e x a m p l e i m p o r t g r a i l s . r e s t . * @ R e s o u r c e ( u r i = ' / c o n t a c t s ' , f o r m a t s = [ ' j s o n ' , ' x m l ' ] ) c l a s s C o n t a c t { S t r i n g f i r s t N a m e S t r i n g l a s t N a m e S t r i n g j o b T i t l e S t r i n g p h o n e N u m b e r A d d r e s s a d d r e s s s t a t i c c o n s t r a i n t s = { } } 

Declaring the resource in UrlMappings.groovy or or " / c o n t a c t s " ( r e s o u r c e s : ' c o n t a c t ' ) " / c o n t a c t s " ( r e s o u r c e s : ' c o n t a c t ' , e x c l u d e : [ ' d e l e t e ' ] ) " / c o n t a c t s " ( r e s o u r c e s : ' c o n t a c t ' , i n c l u d e : [ ' i n d e x ' , ' s h o w ' ] ) 

Default URL patterns HTTP Method URI Grails Action GET /contacts index GET /contacts/create create POST /contacts save GET /contacts/${id} show GET /contacts/${id}/edit edit PUT /contacts/${id} update DELETE /contacts/${id} delete 

Nested Resources " / c o n t a c t s " ( r e s o u r c e s : ' c o n t a c t ' ) { " / a d d r e s s e s " ( r e s o u r c e s : " a d d r e s s " ) } 

Default Nested Resrouce URL patterns HTTP Method URI Grails Action GET /contacts/{$id}/addresses index GET /contacts/{$id}/addresses/create create POST /contacts/{$id}/addresses save GET /contacts/{$id}/addresses/${id} show GET /contacts/{$id}/addresses/${id}/edit edit PUT /contacts/{$id}/addresses/${id} update DELETE /contacts/{id}/addresses/${id} delete 

Versioning APIs or " / c o n t a c t s / v 1 " ( r e s o u r c e s : " c o n t a c t " , n a m e s p a c e : ' v 1 ' ) " / c o n t a c t s / v 2 " ( r e s o u r c e s : " c o n t a c t s " , n a m e s p a c e : ' v 2 ' ) " / b o o k s " ( v e r s i o n : ' 1 . 0 ' , r e s o u r c e s : " b o o k " , n a m e s p a c e : ' v 1 ' ) " / b o o k s " ( v e r s i o n : ' 2 . 0 ' , r e s o u r c e s : " b o o k " , n a m e s p a c e : ' v 2 ' ) 

More options Using the RestController super class Implementing a REST controller from scratch Using a generated REST controller form the scaffold plugin 

Hypermedia as the Engine of Application State Allows the idea of a 'uniform interface' for REST. Services are self documenting and describing in the sense that each resource gives the clients the links necessary to change the state of that resource. 

JSON+HAL example H T T P / 1 . 1 2 0 0 O K S e r v e r : A p a c h e - C o y o t e / 1 . 1 C o n t e n t - T y p e : a p p l i c a t i o n / v n d . b o o k s . o r g . b o o k + j s o n ; c h a r s e t = I S O - 8 8 5 9 - 1 { " _ l i n k s " : { " s e l f " : { " h r e f " : " h t t p : / / l o c a l h o s t : 8 0 8 0 / m y a p p / b o o k s / 1 " , " h r e f l a n g " : " e n " , " t y p e " : " a p p l i c a t i o n / v n d . b o o k s . o r g . b o o k + j s o n " } " p u b l i s h e r " : { " h r e f " : " h t t p : / / l o c a l h o s t : 8 0 8 0 / m y a p p / b o o k s / 1 / p u b l i s h e r " , " h r e f l a n g " : " e n " } } , " t i t l e " : " " T h e S t a n d " " } 

Custom MIME types i m p o r t g r a i l s . r e s t . r e n d e r . h a l . * b e a n s = { h a l C o n t a c t R e n d e r e r ( H a l J s o n R e n d e r e r , g r a i l s . e x a m p l e . C o n t a c t ) } g r a i l s . m i m e . t y p e s = [ a l l : " * / * " , b o o k : " a p p l i c a t i o n / v n d . b o o k s . o r g . b o o k + j s o n " , b o o k L i s t : " a p p l i c a t i o n / v n d . b o o k s . o r g . b o o k l i s t + j s o n " , … ] i m p o r t g r a i l s . r e s t . r e n d e r . h a l . * i m p o r t o r g . c o d e h a u s . g r o o v y . g r a i l s . w e b . m i m e . * b e a n s = { h a l B o o k R e n d e r e r ( H a l J s o n R e n d e r e r , r e s t . t e s t . B o o k , n e w M i m e T y p e ( " a p p l i c a t i o n / v n d . b o o k s . o r g . b o o k + j s o n " , [ v : " 1 . 0 " h a l B o o k L i s t R e n d e r e r ( H a l J s o n C o l l e c t i o n R e n d e r e r , r e s t . t e s t . B o o k , n e w M i m e T y p e ( " a p p l i c a t i o n / v n d . b o o k s . o r g . b o o k l i s t + j s o n " } 

Non REST stuff in 2.3 Changed resolver from ivy to maven Declarative transaction declaration Forked execution mode for speedier test Hibernate 4 

Metrics gathering No metrics collection by default for grails applications Yammer Metrics Plugin New Relic Custom code 

Dropwizard Main Benefits Dead simple deployments Built in metrics collection Smaller than grails No Spring More choices made for you 

Grails Main Benefits Great Community Large Library of Plugins Less opiniated More Conventions Supports HATEOAS and XML 

Conclusion There is no spoon. 

References Dropwizard User Guide Dropwizard User Group https://github.com/codahale/dropwizard Presentation about Dropwizard @ Yammer Presentation about Dropwizard @ Simple Coda Hale and Metrics Coda Hale and the Programming Ape Grails 2.3 REST improvements 

Code we've Looked at Presentation and Example Code Swagger Enhanced Groovy Doc swagger­jaxrs­doclet 

Thanks A special thanks to the people who actually figured all this stuff out. Including but not limited to: Chad Small Sairam Rekapalli Ryley Gahagan Charlie Knudsen John Engelman 

Technical Lead @ Bloomhealth [email protected] @kyleboon http://www.kyleboon.org Kyle Boon