JVM. quack() or Groovy vs Ceremony

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Stas ShevchenkoJava Launch, 23/04/2013, Riga

Java Language comes with

• Design Patterns• Boilerplate• Overly Ceremony code

1. Patterns

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Boilerplate

2. Boilerplate

- getter/setters- Lazy init factories- toString, hashCode, equals- Explicit Exception declaration/handling- Close for resources- synchronization

Ceremony: Code’s Worst Enemy

Code Today (Death Star)

CEREMONY

ESSENCE

Future: Paradigm, Languages, Frameworks

CEREMONY

ESSENCE

3. Ceremony to Essence code. Step 0

public ActionForward edit(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception { PersonForm personForm = (PersonForm) form; if (personForm.getId() != null) { PersonManager mgr = (PersonManager) getBean("personManager"); Person person = mgr.getPerson(personForm.getId()); personForm = (PersonForm) convert(person); updateFormBean(mapping, request, personForm); } return mapping.findForward("edit"); }

Step 1. Duck Typing

edit(mapping, form, request, response) throws Exception { personForm = form; if (personForm.getId() != null) { mgr = getBean("personManager"); person = mgr.getPerson(personForm.getId()); personForm = convert(person); updateFormBean(mapping, request, personForm); } return mapping.findForward("edit"); }

Step 2. duck typing, without local variable

edit(mapping, form, request, response) throws Exception { if (form.getId() != null) { mgr = getBean("personManager"); person = mgr.getPerson(form.getId()); form = convert(person); updateFormBean(mapping, request, form); } return mapping.findForward("edit"); }

Step 3. Implicit return, exceptions

edit(mapping, form, request, response) { if (form.getId() != null) { mgr = getBean("personManager"); person = mgr.getPerson(form.getId()); form = convert(person); updateFormBean(mapping, request, form); } mapping.findForward("edit"); }

Step 4. Don't add a manager layer to MVC (yet). KISS + YAGNI.

edit(mapping, form, request, response) { if (form.getId() != null) { person = Person.find(form.getId()); form = convert(person); updateFormBean(mapping, request, form); } mapping.findForward("edit"); }

Step 5. Conditionals make code expensive to test

edit(mapping, form, request, response) { person = Person.find(form.getId()); form = convert(person); updateFormBean(mapping, request, form); mapping.findForward("edit"); }

Step 6. All action methods have the same four arguments

edit() { person = Person.find(form.getId()); form = convert(person); updateFormBean(mapping, request, form); mapping.findForward("edit"); }

Step 7. Delegate object showing to form

edit() { person = Person.find(form.getId()); mapping.findForward("edit"); }

Step 8. Standard routing

edit() { person = Person.find(form.getId()); }

Or Rubydef edit @person = Person.find(params[:id]) end

Java Word

IoCAspectsLombok or Eclipse XtendCode generators -> Spring Roo

JVM Languages

ClojureScala

GroovyJRubyJython

Java Script

Clojure- Lisp – WTF?- By default Functional Programming only

Scala- Syntax WTF- Acclimatization period 6 to 12 months

JRuby- Ruby guys - gemns hell

Jython- Python syntax ((

Java Script (Rhino)- Is Java Script

Starting Groovy

1. Download the .zip file from http://groovy.codehaus.org and unzip it to local drive

2. Create the GROOVY_HOME environment variable and add $GROOVY_HOME/bin to you path

3. type groovy -version

Groovy Console

Primitives

3.times { println it }

assert (10 instanceof Integer)

println 4.4.class

String s = 10 as String;println s;

Groovy Beans

class Customer { Integer id def name Date dob}

def customer = new Customer(id:1, name:"Gromit", dob:new Date())

Collections – Lists, Ranges

def list = [5, 6, 7, 8]assert list[2] == 7assert list instanceof java.util.List

def range = 5..8assert range.size() == 4assert range[2] == 7assert range instanceof java.util.List

Collections - Map

def map = [name:"Gromit", likes:"cheese", id:1234]assert map["name"] == "Gromit"assert map['id'] == 1234assert map instanceof java.util.Map

Collections features

assert [1, 3, 5] == ['a', 'few', 'words']*.size()

def words = ['ant', 'buffalo', 'cat', 'dinosaur']assert words.findAll{ w -> w.size() > 4 } == ['buffalo', 'dinosaur']

def words = ['ant', 'buffalo', 'cat', 'dinosaur']assert words.collect{ it[0] } == ['a', 'b', 'c', 'd']

def sub = list[1, 3, 20..25, 33]assert sub == [101, 103, 120, 121, 122, 123, 124, 125, 133]

Duck typing

// Hey duckDuck myDuck = new Duck()myDuck.quack()

// Hey quackerdef duck = new Duck()myDuck.quack()

Duck typing 2

class Duck { def quack() {println("quack")}}

def action = "quack"def duck = new Duck()duck."${action}"()

Operators

a == b a.equals(b)a + b a.plus(b)a - b a.minus(b)a++ a.next()a << b a.leftShift(b)

def groovy = [”beer", ”rock&roll"]groovy << ”girls"

Closures

def squareClosure = { value -> value * value;}

assert (4 == squareClosure(2))

IO

def file = new File(sms.txt).eachLine{ println it }

file.write(”rewrite file”)

file.append(“add to file”)file << ”sexy style"

XML

def xml = new groovy.xml.MarkupBuilder()xml.goods(type:”current”){ good(“Beer”) good (“Rock&Roll”) good (“Girls”)}

XML

def goods = new XmlSlurper().parseText(…)def allGoods = records.nameassert 3 == allRecords.size()def allNodes = goods.depthFirst().collect{ it }def firstGood = goods.name[0]assert ’sms’ == firstGood .name()assert ‘Text’ == firstGood.@make.text()

DSL

This is a really cool topic, where the stars are began…

• A DSL allows expressions in a domain specific manner

• Method pointers make this easy:def list = []def insert = list.&addinsert ”beer"insert ”rock&roll"

Something to read

Groovy++Grails -> GORMGradle

At the end – NPE fighter in my team

infringementAction.setCustomsOffice( versionedReplyInf != null ? (versionedReplyInf.getReplyInf() != null ? (versionedReplyInf.getReplyInf().getInf() != null ? (versionedReplyInf.getReplyInf().getInf().getInf() != null ? (versionedReplyInf.getReplyInf().getInf().getInf().

getCustomsOffice() != null ? versionedReplyInf.getReplyInf().getInf().getInf().

getCustomsOffice() : null) : null) : null) : null) : null);

At the end on Groovy

Safe navigation operator “?.”

infringementAction.setCustomsOffice(versionedReplyInf?.getReplyInf()?.getInf()?.getInf()?.getCustomsOffice())