Cooking your own Groovy Builder: A step forward into Domain-Specific Languages Ixchel Ruiz, PSE CCA Andres Almiray, PSE Oracle BOF-5102

Learn to empower your code with the expressiveness of Groovy’s Builders

Learn to empower your code with the expressiveness of Groovy’s Builders

Agenda Builders and Groovy Life without builders Swing demo Java2D demo FactoryBuilderSupport Resources

Builders and Groovy

Life without builders

Swing demo

Java2D demo

FactoryBuilderSupport

Resources

Why Groovy? It is so Cool ! No impedance mismatch with Java Groovy is Java Flat learning curve If you are a Java programmer, congratulations! you are also a Groovy programmer

It is so Cool !

No impedance mismatch with Java

Groovy is Java

Flat learning curve

If you are a Java programmer, congratulations! you are also a Groovy programmer

Builders Provide an abstraction layer Increase Expressiveness Better suited to express hierarchical data Simplify Development

Provide an abstraction layer

Increase Expressiveness

Better suited to express hierarchical data

Simplify Development

Why builders for DSLs? Domain-Specific Languages can be written with Groovy in many ways. Metaprogramming Fluent Interface, static imports, closures Builders

Domain-Specific Languages can be written with Groovy in many ways.

Metaprogramming

Fluent Interface, static imports, closures

Builders

Builders for DSLs Builders are a great choice to begin with Pretty straight forward structure No heavy metaprogramming required Groovy provides 2 base classes to get you started BuilderSupport FactoryBuilderSupport

Builders are a great choice to begin with

Pretty straight forward structure

No heavy metaprogramming required

Groovy provides 2 base classes to get you started

BuilderSupport

FactoryBuilderSupport

The Dark Side Life without builders

Life without builders

Swing How many lines of code may this little program require in plain Java?

How many lines of code may this little program require in plain Java?

Groovy’s answer import groovy.swing.SwingBuilder import java.awt.BorderLayout as BL import javax.swing.JOptionPane SwingBuilder.build { frame( id: 'frame', title: 'Hello World', show: true, pack: true ){ borderLayout() label( 'Enter a message:', constraints: BL.WEST ) textField( id: 'name', columns: 20, constraints: BL.CENTER ) button( 'Click', constraints: BL.EAST, actionPerformed: { e -> if( !name.text ) return JOptionPane.showMessageDialog( frame, name.text ) }) } }

import groovy.swing.SwingBuilder

import java.awt.BorderLayout as BL

import javax.swing.JOptionPane

SwingBuilder.build {

frame( id: 'frame', title: 'Hello World', show: true, pack: true ){

borderLayout()

label( 'Enter a message:', constraints: BL.WEST )

textField( id: 'name', columns: 20, constraints: BL.CENTER )

button( 'Click', constraints: BL.EAST, actionPerformed: { e ->

if( !name.text ) return

JOptionPane.showMessageDialog( frame, name.text )

})

}

}

Java2D This is a Java2D drawing that started as a rounded rectangle

How many lines of code would it take in plain Java? Short answer: didn’t even bother to measure them The complete example has a little animation, applying each filter at a time, wonder how much code would be needed

Short answer: didn’t even bother to measure them

The complete example has a little animation, applying each filter at a time, wonder how much code would be needed

Groovy’s answer antialias on rect( x: 20, y: 20, width: 180, height: 160, arcWidth: 50, arcHeight: 50, borderColor: no, id: 'base' ){ linearGradient { stop( offset: 0.5, color: 'white' ) stop( offset: 1, color: 'blue' ) } filters( offset: 50 ){ weave() kaleidoscope( sides: 4 ) shapeBurst( merge: true, type: 'circle up' ) lights(){ ambientLight( color: color('lime').rgb(), centreX: 0, centreY: 0 ) } dropShadow() } }

antialias on

rect( x: 20, y: 20, width: 180, height: 160,

arcWidth: 50, arcHeight: 50, borderColor: no, id: 'base' ){

linearGradient {

stop( offset: 0.5, color: 'white' )

stop( offset: 1, color: 'blue' )

}

filters( offset: 50 ){

weave()

kaleidoscope( sides: 4 )

shapeBurst( merge: true, type: 'circle up' )

lights(){

ambientLight( color: color('lime').rgb(),

centreX: 0, centreY: 0 )

}

dropShadow()

}

}

What is going on? As with other builders, each node is actually a “pretended” method Pretended methods are routed through the build cycle, any other methods are handled as usual SwingBuilder node names are easy to remember, most of the time just remove the leading ‘J’ from a Swing class and that’s it Both SwingBuilder and GraphicsBuilder extend from FactoryBuilderSupport

As with other builders, each node is actually a “pretended” method

Pretended methods are routed through the build cycle, any other methods are handled as usual

SwingBuilder node names are easy to remember, most of the time just remove the leading ‘J’ from a Swing class and that’s it

Both SwingBuilder and GraphicsBuilder extend from FactoryBuilderSupport

FactoryBuilderSupport at a glance Factories have the responsibility to handle pretended methods Each factory hooks into the build cycle The builder will notify the current building factory whenever an action on the node should be taken Each factory has it own context for storing useful information while building nodes

Factories have the responsibility to handle pretended methods

Each factory hooks into the build cycle

The builder will notify the current building factory whenever an action on the node should be taken

Each factory has it own context for storing useful information while building nodes

What factories may control Node creation Setting attributes on the node If the node accepts children Adding the node to its parent node Processing the closure by themselves or let the builder handle it Node completion

Node creation

Setting attributes on the node

If the node accepts children

Adding the node to its parent node

Processing the closure by themselves or let the builder handle it

Node completion

Available context properties (1) context : retrieves the current context current : reference to the current node currentName : the “pretended” method name currentFactory : reference to the factory that built the current node

context : retrieves the current context

current : reference to the current node

currentName : the “pretended” method name

currentFactory : reference to the factory that built the current node

Available context properties (2) Similar properties if a parent node is available parentContext : retrieves the parent’s context parentNode : reference to the parent node parentName : the parent’s node name parentFactory : reference to the parent’s factory

Similar properties if a parent node is available

parentContext : retrieves the parent’s context

parentNode : reference to the parent node

parentName : the parent’s node name

parentFactory : reference to the parent’s factory

Extension Points FactoryBuilderSupport exposes the following extension points via closure delegates Pre node creation Post node creation Attribute handling Node completion End of build cycle

FactoryBuilderSupport exposes the following extension points via closure delegates

Pre node creation

Post node creation

Attribute handling

Node completion

End of build cycle

Adding css to Swing, how? We can’t extend every swing component available, that’s overkill We can’t also extend every factory for the same reason But we can use an attribute delegate that handles css attributes

We can’t extend every swing component available, that’s overkill

We can’t also extend every factory for the same reason

But we can use an attribute delegate that handles css attributes

This is one way to do it import groovy.swing.* import com.u2d.css4swing.CSSEngine import com.u2d.css4swing.style.ComponentStyle CSSEngine.initialize() SwingBuilder.build { addAttributeDelegate { builder, node, attributes -> def cssClass = attributes.remove("cssClass") if( cssClass ) ComponentStyle.addClass( node, cssClass ) } frame( id: 'fame', size: [300,100], locationRelativeTo: null, title: 'CSS+ Swing + Groovy', show: true ){ gridLayout( cols: 1, rows: 2 ) label( 'This is not important' ) label( 'This is really important', cssClass: 'important' ) } }

import groovy.swing.*

import com.u2d.css4swing.CSSEngine

import com.u2d.css4swing.style.ComponentStyle

CSSEngine.initialize()

SwingBuilder.build {

addAttributeDelegate { builder, node, attributes ->

def cssClass = attributes.remove("cssClass")

if( cssClass ) ComponentStyle.addClass( node, cssClass )

}

frame( id: 'fame', size: [300,100], locationRelativeTo: null,

title: 'CSS+ Swing + Groovy', show: true ){

gridLayout( cols: 1, rows: 2 )

label( 'This is not important' )

label( 'This is really important', cssClass: 'important' )

}

}

Live code session

For More Information http:// groovy.codehaus.org The builders http:// groovy.codehaus.org/FactoryBuilderSupport http:// groovy.codehaus.org/ObjectGraphBuilder http:// groovy.codehaus.org/Swing+Builder http:// groovy.codehaus.org/SwingXBuilder http:// groovy.codehaus.org/JideBuilder http://groovy.codehaus.org/GraphicsBuilder http://groovy.codehaus.org/Using+Ant+from+Groovy http://groovy.codehaus.org/Creating+XML+using+Groovy's+MarkupBuilder http:// jroller.com/aalmiray

http:// groovy.codehaus.org

The builders

http:// groovy.codehaus.org/FactoryBuilderSupport

http:// groovy.codehaus.org/ObjectGraphBuilder

http:// groovy.codehaus.org/Swing+Builder

http:// groovy.codehaus.org/SwingXBuilder

http:// groovy.codehaus.org/JideBuilder

http://groovy.codehaus.org/GraphicsBuilder

http://groovy.codehaus.org/Using+Ant+from+Groovy

http://groovy.codehaus.org/Creating+XML+using+Groovy's+MarkupBuilder

http:// jroller.com/aalmiray

Andres Almiray, PSE Oracle Ixchel Ruiz, PSE CCA BOF-5102