Groovy in the Enterprise:Case Studies

Guillaume LaforgeVP TechnologyG2One, Inc.glaforge@g2one.com

Guillaume Laforge

Groovy Project Manager

• Spec Lead of JSR-241

Initiator of the Grails framework

Co-author of Groovy in Action

VP Technology at G2One

• The Groovy / Grails company

• Training, support, consulting

Evangelizing Groovy, Grails and DSLs

• JavaOne, JavaPolis, QCon, JAX, Sun TechDays...

Goal of this talk

Discover real-world Groovy usage in the Enterprise to better understand:

•How you can leverage Groovy in your own environment

•How to integrate Groovy

in your applications

Agenda

About Groovy and Grails

Groovy usage patterns

Integrating Groovy in your applications

Case studies

About Groovy and Grails

Groovy, a dynamic language for the JVMGrails, an agile web application framework

Groovy is...

The fastest dynamic language for the JVM

• that integrates seamlessly with Java

without any impedance mismatch

An Apache-licensed Open Source project

• successful project hosted at Codehaus

Aiming at simplifying the life of developers

• by bringing expressiveness and productivity boosts

• by borrowing good ideas from other languages

An innovative and creative project

Java-like on steroids

Syntax derived from the Java 5 grammar

• Flat learning curve for Java developers

• Supports both static and dynamic typing

Support Java 5 features

• Annotations, generics, static imports, enums...

• Sole dynamic language to support this!

Real full Java / Groovy interop

• Joint compiler

• or can be evaluated on the fly

JInterface

<<implements>>

GClass

JClass

GInterface

JClass

GClass

<<implements>>

A Java programimport java.util.List;import java.util.ArrayList;class Erase { private List filterLongerThan(List strings, int length) { List result = new ArrayList(); for (int i = 0; i < strings.size(); i++) { String s = (String) strings.get(i); if (s.length() <= length) { result.add(s); } } return result; } public static void main(String[] args) { List names = new ArrayList(); names.add("Ted"); names.add("Fred"); names.add("Jed"); names.add("Ned"); System.out.println(names); Erase e = new Erase(); List shortNames= e.filterLongerThan(names, 3); System.out.println(shortNames.size()); for (inti= 0; i< shortNames.size(); i++) { String s = (String) shortNames.get(i); System.out.println(s); } }}

A Groovy programimport java.util.List;import java.util.ArrayList;class Erase { private List filterLongerThan(List strings, int length) { List result = new ArrayList(); for (int i = 0; i < strings.size(); i++) { String s = (String) strings.get(i); if (s.length() <= length) { result.add(s); } } return result; } public static void main(String[] args) { List names = new ArrayList(); names.add("Ted"); names.add("Fred"); names.add("Jed"); names.add("Ned"); System.out.println(names); Erase e = new Erase(); List shortNames= e.filterLongerThan(names, 3); System.out.println(shortNames.size()); for (inti= 0; i< shortNames.size(); i++) { String s = (String) shortNames.get(i); System.out.println(s); } }}

A more idiomatic Groovy solution

def names = [“Ted”, “Frend”, “Jed”, “Ned”]println namesdef shortNames = names.findAll { it.size() <= 3 }println shortNames.size()shortNames.each { println it }

Features at a glance...

Don’t wait for Java 7, 8, 9

• closures, properties, collection & regex literals

Operator overloading

• Just method calls: plus(), multiply(), etc.

• BigDecimal arithmetics by default

Metaprogramming — useful for DSLs

• Property / method calls interception

Optional semicolons and parentheses

SQL, Ant, XML, templates, Swing, JMX...

Lots to read to learn more!

Grails

Groovy usage patterns

A tool in the developer toolboxA full stack web application frameworkAn extension point in your applicationDomain-Specific Languages

Pattern: Developer tool

Great support for unit testing and mock objects

• Nice way to introduce Groovy in a project

Shell scripting reusing all your JARs

• Easy to control Ant task for custom builds

Template engine for code generation needs

Excellent XML parsing and creation support

Easy JDBC for import/export database scripts

Pattern: CoC web app development

Convention over Configuration

• Productive in minutes with scaffolding

• No useless configuration, focus on what matters

• Dir. layout, naming conventions, transparent wiring...

Grails = Groovy + Spring + Hibernate + ...

• Groovy is the glue to write your views (Groovy Server Pages)

your controllers

your services

your domain classes

Pattern: Application extension point

Customize or extend your application at extension points through Groovy scripting

Create plugins adding new functionality

Add / Update business rules at runtime

• See also Domain-Specific Languages

Personalize your reporting screens

• With Groovy templates

Remote introspection of your app

• Embed a remote Groovy shell

Pattern: Domain-Specific Language

Use a more expressive language

• than a general purpose language

Share a common metaphore between developers and subject matter experts

Domain experts can help write the rules!

Avoid boilerplate technical code

Cleanly seperate business logic from application plumbing code

Integrating Groovy in your applications

JSR-223, one API to rule them allSpring dynamic beansGroovy’s own mechanisms

JSR-223: javax.script.*

One API to rule them all

Groovy engine JAR at scripting.dev.java.net

• drop it in your classpath

ScriptEngineManager mgr = new ScriptEngineManager();ScriptEngine eng = mgr.getEngineByName(“Groovy”);String result = (String)eng.eval(“‘foo’*2”);

Spring 2 dynamic language beans

Spring 2 provides support for alternative language bean definitions & implementations

• POGOs can be wired, proxied, injected in POJOs

Configuration with the <lang:*> namespace

• <lang:groovy id=’bean’ script-source=’classpath:com.foo.GBean’

customizer-ref=’specialMetaClass’/>

Groovy beans can be “refreshed”

Groovy’s own mechanisms

Several integration mechanisms

• Eval, GroovyShell, GroovyScriptEngine

• def binding = new Binding()binding.mass = 22.3binding.velocity = 10.6def shell = new GroovyShell()def expr = “mass * velocity ** 2 / 2”assert shell.evalute(expr) == 1252.814

GroovyClassLoader for more advanced integration scenario

Case studies

Groovy and Grails Success Stories

Grails Examples

LinkedInBSkyB showbiz portal

LinkedIn

Main site

• Java / Tomcat / Spring / Hibernate / custom MVC

But their corporate solutions are in Grails

• Private portals for recruiters, for premium customers with focused needs

Why Grails?

• Needed a more productive webapp framework with rapid prototyping capabilities

• Needed deep integration with their Java backend custom session, reuse business services, SSO

showbiz

Biggest UK satellitebroadcaster

• also known as BSkyB

• owned by News Corp.

Developed their showbiz website on Grails

• 186+ million page views per month

• “Grails just scales” ™

Currently rewriting their main portal in Grails

Groovy as a Developer Tool

Patterson Institute for Cancer ResearchFrench Ministry of JusticeCanoo WebTest

Patterson Institute for Cancer Research

Manchester University / Cancer Research UK

Groovy in two projects

• X:Map: a Genome browser using a 54GB tileset for Google Maps

• exonmap: microarrays analysis program

Groovy used to

• Fetch latest genome sequencing information (FTP)

• Homogenize data sources

• Scan databases, extrapolate and filter data

Code generation

Groovy was used as a developer tool

• but no line of Groovy in production code

GroovyTemplateEngine

UMLXMI

Groovy XMLParsers

Canoo WebTest

Open Source tool for automating testing of web applications

invoke “http://google.com”verifyTitle “Google”setInputField name: ‘q’, value: ‘WebTest’clickButton “I’m feeling lucky”verifyTitle “Canoo WebTest”

Groovy as a Language for Application Extension Points

CodeStreet Market Data StudioHyperic HQ

codestreet

Market Data Works simplifies

• capturing, auditing

• editing Reuters market data

Traders can use Groovy

• modify market data feeds

• record and replay feeds

• test evolutionary scenario

Groovy

Hyperic HQ: open source web infrastructure monitoring and management suite

• used in Spring Application Management Suite

Big Groovy-based plugin infrastructure

• script deployments, server reboots, threshold alerts,

resources monitoring, etc...

• agent side: custom handling of monitored resources

• also embeds a Groovy console for interactive work

• plugins updatable / reloadable at runtime

Groovy for Business Rules and DSLs

Mutual of OmahaNational Cancer InstituteIRSNOCTO Technology

Mutual of Omaha

US Fortune 500 insurance company

Risk calculation engine in Groovypart of a mission-critical application

50,000 lines of Groovy code

• half business rules, half test code

Module part of a large EJB-based application

Choice of Groovy

• Business rules readability, maintenance by IT and Subject Matter experts, seamless Java integration

Mutual of Omaha

On business rules readability...

• Groovy’s BigDecimal support

• Simple interpolation formula (d*(b-c)+e*(c-a))/(a-b)

BigDecimal uMinusv = upperBound.subtract(value); BigDecimal vMinusl = value.subtract(lowerBound); BigDecimal uMinusl = upperBound.subtract(lowerBound); return lowerValue.multiply(uMinusv). add(upperValue.multiply(vMinusl)). divide(uMinusl, 10, BigDecimal.ROUND_HALF_UP);

(lowerValue * (upperBound-value) + upperValue * (value-lowerBound) ) / (upperBound-lowerBound)

National Cancer Institute

Cancer registry management

• Organizes large amounts of medical records

• JBoss / Oracle / Hibernate / Struts application

Groovy used in several places

• As an architecture validation system — dev. tool ensure proper layer seperation, if not, fail the build

• Param validation for customizing reporting screens

• Business rules to edit and validation medical records validity of fields, of set of fields, of records

check / fix / improve the patient files

700k patient files * 1,300 edits

Nuclear safety organization

Scientific context, with intensiveand complex computation needs

Matlab/Mathematica-like DSL on top of super efficient Java custom math library

• Thin Groovy DSL layer

• Enjoyed a math-like syntax for matrices, seamless

integration with Java

• Groovy’s operator overloading mechanism

• Friendlier to scientists and mathematicians

• Application targets 200-300 engineers & researchers

Human Resources DSL

Architecture / Agile consultancy

• Needed a way to track consultant skills & knowledge pay raises, finding the right person for the gig, etc...

Developed a DSL to represent skills

• Textual DSL transformed into a treemap-like graphics

• Integrated in Confluence as a plugin the plugin parses and generates an in-memory model

a servlet renders graphics to embed in the wiki pages

a Confluence macro renders everything on the wiki page

• Leverages Confluence’s search capabilities

Human Resources DSL

etre { idees { capture 1 formule 1 produit 1 } organisation { controle 1 abandonne 1 aligne 1 } engagement { euros 1 gens 1 idees 1 enseigner 1 }}faire { ...}

Summary

Summary

Groovy is a successful, mature and performant dynamic language for the JVM

Provides several interesting usage patterns

• Developer tool, CoC webapp development,

application extension mechanism, DSLs & business rules externalization

Used in production for mission-critical

applications, and integrated in many frameworks

Questions & Answers

glaforge @ .com