Groovy vs Boilerplate and Ceremony Code

JVM. quack() or Groovy vs Ceremony

…
Stas Shevchenko
Java Launch, 23/04/2013, Riga

Java Language comes with
• Design Patterns
• Boilerplate
• Overly Ceremony code

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)

ESSENCE

CEREMONY

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);
}
}

Step 2. duck typing, without local
variable
edit(mapping, form, request, response)
throws Exception {
if (form.getId() != null) {
person = mgr.getPerson(form.getId());
form = convert(person);
updateFormBean(mapping, request, form);
}
}

Step 3. Implicit return, exceptions
edit(mapping, form, request, response) {
person = mgr.getPerson(form.getId());
}
mapping.findForward("edit");
}

Step 4. Don't add a manager layer to
MVC (yet). KISS + YAGNI.
person = Person.find(form.getId());
}
}

Step 5. Conditionals make code
expensive to test
}

Step 6. All action methods have the
same four arguments
edit() {
}

Step 7. Delegate object showing to
form
edit() {
}

Step 8. Standard routing
edit() {
}

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

Java Word
IoC
Aspects
Lombok or Eclipse Xtend
Code generators -> Spring Roo

JVM Languages
Clojure
Scala
Groovy
JRuby
Jython
Java Script

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

Scala
- Syntax WTF
- Acclimatization period 6 to 12 months

JRuby
- Ruby guys
- gemns hell

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

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] == 7
assert list instanceof java.util.List

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

Collections - Map
def map = [name:"Gromit", likes:"cheese",
id:1234]
assert map["name"] == "Gromit"
assert map['id'] == 1234
assert 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 duck
Duck myDuck = new Duck() myDuck.quack()

// Hey quacker
def 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.name
assert 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.&add insert ”beer" insert
”rock&roll"

Something to read
Groovy++
Grails -> GORM
Gradle

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())

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