Groovy Introduction

What makes me like Groovy

Run groovy as scripts

$ groovy -e "println 'Hello, Groovy.'"
$ groovy myScript.groovy

# Faster using groovy server (JVM re-use)
$ groovyclient -e "println 'Hello, GroovyServ.'"

Run groovy in Intellij

(even community edition)

Run groovy on the web

https://groovyconsole.appspot.com

Integrate Groovy classes into maven project

Place groovy files in /src/main/groovy

  2.3.4
  1.3
  grvy
  true

  org.codehaus.gmaven
  gmaven-plugin
  ${gmaven-version}
  
      
          
              generateStubs
              compile
              generateTestStubs
              testCompile
          
          
              1.7
          
      
  
  
      
          org.codehaus.gmaven.runtime
          gmaven-runtime-1.7
          1.3
          
              
                  org.codehaus.groovy
                  groovy-all
              
          
      
      
          org.codehaus.groovy
          groovy-all
          ${groovy-version}
      
  

Strings

def name = "Xavier"
println "My name is $name"

assert "Xavier" == "Mon nom est Xavier."[12..17]
assert "Xavier" == "Mon nom est Xavier."[12..-2]

int i = "18".toInteger()

//Multiline
def str = """
	Lorem Ipsum is simply dummy text of the printing
	and typesetting industry.
	Lorem Ipsum has been the industry's
	standard dummy text ever since the 1500s
"""

Constructor

class Person {
	String name
	int age
}
new Person(name:"Xavier", age:21)

def map = [
	"name":"Xavier",
	"age":21
]
new Person(map)
	

Collections

assert [] instanceof ArrayList
assert [1, 2] + [3, 4] == [1, 2, 3, 4]

def names = ["Xavier", "Lenny"]
names.each {name -> println name}
names.each {println it}
names.eachWithIndex { String name, int i -> println "$i:$name"}
names.collect{name -> "Hi $name"}

names.find {it.startsWith("X")}
names.findAll {it.length() > 3}

names.groupBy {it[0]}."X".size() // => 1
def (beforeM, afterM) = names.split { it[0] < "M"}
assert beforeM == ["Lenny"] && afterM == ["Xavier"]

//create a closure and apply it on the collection
def p = {o -> println "${new Date()}...$o"}
names.each(p)

//chain
"xavier-lenny".split("-").collect { it.toUpperCase() }.join(";").with(p)
	

Files

//read the whole content of a file
def body = new File("file-name.txt").text

//and same for write
new File("file-name.txt").text = "this is a file body \n second line"

new File('/path/to/file').eachLine('UTF-8') { println it }

def myCsvFile = new File("/tmp/a.csv")
myCsvFile.text = """author;age\nXavier;29\nLenny;7"""

myCsvFile.splitEachLine(";", { f ->
     println "${f[0]}-${f[1]}"
})

myCsvFile.readLines().size() == 3
	

Json (out of the box)

//Sample file for testing
def myFile = new File("/tmp/a.json")
myFile.text = """{"name":"Xavier", "age":29}"""

//Json to Object from File or from String
def author = new JsonSlurper().parse(myFile)
author = new JsonSlurper().parseText(myFile.text)
assert author instanceof Map

//Edit the map
author.age = 30

//Object to Json
myFile.text = new JsonBuilder(author).toString()
println myFile.text
// => {"age":30,"name":"Xavier"}
		

Xml (out of the box)

//Sample file for testing
def myXmlFile = new File("/tmp/a.xml")
myXmlFile.text = """Xavier"""

//Json to Object from File or from String
def authorX
authorX = new XmlSlurper().parse(myXmlFile)    //SAX
authorX = new XmlParser().parse(myXmlFile)     //DOM
authorX = new XmlParser().parseText(myXmlFile.text)
assert authorX instanceof Map

assert authorX.name == "Xavier"
assert authorX.@age == 30
			

Multi thread

def list = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16]
withPool( 10 ) {
  list.eachParallel { elm, idx ->
      println "Working on elt:$elm at idx:$idx"
  }
  println "Fork/join and wait all tasks to finish... Done ! "
}
		

Thank you