Real Life Groovy

Paul Bakker

What I wish this talk is about

Introduction

Introduction

What this talk actually is about

About me

Paul Bakker• Trainer Info Support• Java Magazine author• Big time Groovy fan ;-)

EJB 3JSFSeamJavaFXSpringHibernateFlex

Outline

• Freshing up your Groovy knowledge• Real life Groovy examples

–Test Data–Database conversion–Unit Testing

• A leap of faith–A Groovy web service client–Generating XML–A Groovy session bean

• A dynamic language • Compiles to byte code• Running in the JVM• Completely compatible with Java

So what was Groovy again?

Lists

Maps

The Groovy 101Closures

Meta Programming:The Expando

Meta Programming:Changing behavior at runtime

Groovy’s strong points

• Working with collections• Changing behavior at runtime• The builder pattern• It’s all just Java

Generating test data

• Populate a database with test data• Automated & Repeatable• You might use DBUnit

–That’s a lot of XML...

Generating test data

The problem:Database conversion

Old legacy schema

Redesigned schema for new application

• Reuse most of the data• Don’t loose references• But don’t limit new mappings

The schema

MESSAGEmessage_idsubjectbodyfirstnamelastnameusernameattachment

MESSAGEmessage_idsubjectbodyuser_id

USERuser_idusernamefirstnamelastnameemail

FILEfile_idfilenamedata

ATTACHMENTmessage_idfile_id

*

1

1*

1*

A Groovy SQL script

Running the script

• Compile the script• Jar the class files• Add Groovy.jar dependency• java -jar GroovyDBScript.jar

Unit Testing

• Mocking is really useful–But it’s quite a lot of work

• Groovy’s dynamic nature and Meta Programming helps

The Java class to test

The Java Unit Test

The Groovy Unit Test

Making untestable code testable

• Replace Java code at joint points–Replace direct service calls with a Groovy proxy

Java Class Java Service delegate

Groovy Proxy

A Groovy Service Proxy

Building

Uses Implements

Groovy Joint compiler

groovyc*.groovy*.java‐j‐Jsource=1.4‐Jtarget=1.4

A leap of faith

• Replace some Java code by more readable Groovy code

• XML Converters• A Groovy web service client• A Groovy EJB3 Session bean

A Groovy web service client

Using the Groovy Service

getTitles(“Java”)

[“Effective Java”, ...]

A Groovy Session Bean

Replace any Java code

A warning about domain classes

Don’t forget about the metaClass property

Groovy domain class

ActionScript class

Serialize

MusthavemetaClassproperty!

GANT

• ANT without XML• More natural build definition• Use control structures

• Works in every build environment

Just get the Groove

• Groovy makes a lot of tasks easier• Fits in most environments• Use Groovy where it really adds value

Should we ever write Java code?

• More readable code• Better unit testing• Advanced frameworks

• Not everybody knows Groovy• No static code analysis