Apache Groovy

James Strachan first talked about the development of Groovy on his blog in August 2003.[7] In March 2004, Groovy was submitted to the JCP as JSR 241[8] and accepted by ballot. Several versions were released between 2004 and 2006. After the Java Community Process (JCP) standardization effort began, the version numbering changed, and a version called "1.0" was released on January 2, 2007. After various betas and release candidates numbered 1.1, on December 7, 2007, Groovy 1.1 Final was released and immediately renumbered as Groovy 1.5 to reflect the many changes made.

In 2007, Groovy won the first prize at JAX 2007 innovation award.[9] In 2008, Grails, a Groovy web framework, won the second prize at JAX 2008 innovation award.[10]

In November 2008, SpringSource acquired the Groovy and Grails company (G2One).[11] In August 2009 VMware acquired SpringSource.[12]

In April 2012, after eight years of inactivity, the Spec Lead changed the status of JSR 241 to dormant.[8]

Strachan had left the project silently a year before the Groovy 1.0 release in 2007. In Oct 2016, Strachan stated "I still love groovy (jenkins pipelines are so groovy!), java, go, typescript and kotlin".[13]

On July 2, 2012, Groovy 2.0 was released, which, among other new features, added static compiling and static type checking.

When the Pivotal Software joint venture was spun-off by EMC Corporation (EMC) and VMware in April 2013, Groovy and Grails formed part of its product portfolio. Pivotal ceased sponsoring Groovy and Grails from April 2015.[5] That same month, Groovy changed its governance structure from a Codehaus repository to a Project Management Committee (PMC) in the Apache Software Foundation via its incubator.[6] Groovy graduated from Apache's incubator and became a top-level project in November 2015.[14]

Most valid Java files are also valid Groovy files. Although the two languages are similar, Groovy code can be more compact, because it does not need all the elements that Java needs.[15] This makes it possible for Java programmers to learn Groovy gradually by starting with familiar Java syntax before acquiring more Groovy programming idioms.[16]

Groovy features not available in Java include both static and dynamic typing (with the keyword def), operator overloading, native syntax for lists and associative arrays (maps), native support for regular expressions, polymorphic iteration, string interpolation, added helper methods, and the safe navigation operator ?. to check automatically for null pointers (for example, variable?.method(), or variable?.field).[17]

Since version 2 Groovy also supports modularity (being able to ship only the needed jars according to the project needs, thus reducing the size of Groovy's library), type checking, static compiling, Project Coin syntax enhancements, multicatch blocks and ongoing performance enhancements using the invokedynamic instruction introduced in Java 7.[18]

Groovy provides native support for various markup languages such as XML and HTML, accomplished via an inline Document Object Model (DOM) syntax. This feature enables the definition and manipulation of many types of heterogeneous data assets with a uniform and concise syntax and programming methodology.

Unlike Java, a Groovy source code file can be executed as an (uncompiled) script, if it contains code outside any class definition, if it is a class with a main method, or if it is a Runnable or GroovyTestCase. A Groovy script is fully parsed, compiled, and generated before executing (similar to Python and Ruby). This occurs under the hood, and the compiled version is not saved as an artifact of the process.[19]

class AGroovyBean {
  String color
}

def myGroovyBean = new AGroovyBean()

myGroovyBean.setColor('baby blue')
assert myGroovyBean.getColor() == 'baby blue'

myGroovyBean.color = 'pewter'
assert myGroovyBean.color == 'pewter'

def movieList = ['Dersu Uzala', 'Ran', 'Seven Samurai']  // Looks like an array, but is a list
assert movieList[2] == 'Seven Samurai'
movieList[3] = 'Casablanca'  // Adds an element to the list
assert movieList.size() == 4

def monthMap = [ 'January' : 31, 'February' : 28, 'March' : 31 ]  // Declares a map
assert monthMap['March'] == 31  // Accesses an entry
monthMap['April'] = 30  // Adds an entry to the map
assert monthMap.size() == 4

Number.metaClass {
  sqrt = { Math.sqrt(delegate) }
}

assert 9.sqrt() == 3
assert 4.sqrt() == 2

enum Color {
  BLACK('#000000'), WHITE('#FFFFFF'), RED('#FF0000'), BLUE('#0000FF')
  String hex
  Color(String hex) { 
    this.hex = hex 
  }
}

String.metaClass.getProperty = { String property ->
  def stringColor = delegate
  if (property == 'hex') {
    Color.values().find { it.name().equalsIgnoreCase stringColor }?.hex
  }
}

assert "WHITE".hex == "#FFFFFF"
assert "BLUE".hex == "#0000FF"
assert "BLACK".hex == "#000000"
assert "GREEN".hex == null

take(coffee).with(sugar, milk).and(liquor)

take coffee with sugar, milk and liquor

list = [1, 2, 3, 4, 5, 6, 7, 8, 9]

/* 
 * Non-zero numbers are coerced to true, so when it % 2 == 0 (even), it is false.
 * The type of the implicit "it" parameter can be inferred as an Integer by the IDE.
 * It could also be written as:
 * list.findAll { Integer i -> i % 2 }
 * list.findAll { i -> i % 2 }
 */
def odds = list.findAll { it % 2 }

assert odds == [1, 3, 5, 7, 9]

// This block of code contains expressions without reference to an implementation
def operations = {
  declare 5
  sum 4
  divide 3
  print
}

/* 
 * This class will handle the operations that can be used in the closure above. Another class
 * could be declared having the same methods, but using, for example, webservice operations
 * in the calculations.
 */
class Expression {
  BigDecimal value

  /* 
   * Though an Integer is passed as a parameter, it is coerced into a BigDecimal, as was 
   * defined. If the class had a 'declare(Integer value)' method, it would be used instead.
   */
  def declare(BigDecimal value) {
    this.value = value
  }
  
  def sum(BigDecimal valueToAdd) {
    this.value += valueToAdd
  }
  
  def divide(BigDecimal divisor) {
    this.value /= divisor
  }
  
  def propertyMissing(String property) {
    if (property == "print") println value
  }
}

// Here is defined who is going to respond the expressions in the block of code above.
operations.delegate = new Expression()
operations()

def joinTwoWordsWithSymbol = { symbol, first, second -> first + symbol + second }
assert joinTwoWordsWithSymbol('#', 'Hello', 'World') == 'Hello#World'

def concatWords = joinTwoWordsWithSymbol.curry(' ')
assert concatWords('Hello', 'World') == 'Hello World'

def prependHello = concatWords.curry('Hello')
//def prependHello = joinTwoWordsWithSymbol.curry(' ', 'Hello')
assert prependHello('World') == 'Hello World'

def power = { BigDecimal value, BigDecimal power ->
  value**power
}

def square = power.rcurry(2)
def cube = power.rcurry(3)

assert power(2, 2) == 4
assert square(4) == 16
assert cube(3) == 27

<languages>
  <language year="1995">
    <name>Java</name>
    <paradigm>object oriented</paradigm>
    <typing>static</typing>
  </language>
  <language year="1995">
    <name>Ruby</name>
    <paradigm>functional, object oriented</paradigm>
    <typing>duck typing, dynamic</typing>
  </language>
  <language year="2003">
    <name>Groovy</name>
    <paradigm>functional, object oriented</paradigm>
    <typing>duck typing, dynamic, static</typing>
  </language>
</languages>

def writer = new StringWriter()
def builder = new groovy.xml.MarkupBuilder(writer)
builder.languages {
  language(year: 1995) {
    name "Java"
    paradigm "object oriented"
    typing "static"
  }
  language (year: 1995) {
    name "Ruby"
    paradigm "functional, object oriented"
    typing "duck typing, dynamic"
  }
  language (year: 2003) {
    name "Groovy"
    paradigm "functional, object oriented"
    typing "duck typing, dynamic, static"
  }
}

def languages = new XmlSlurper().parseText writer.toString()

// Here is employed Groovy's regex syntax for a matcher (=~) that will be coerced to a 
// boolean value: either true, if the value contains our string, or false otherwise.
def functional = languages.language.findAll { it.paradigm =~ "functional" }
assert functional.collect { it.name } == ["Groovy", "Ruby"]

BigDecimal account = 10.0
def text = "The account shows currently a balance of $account"
assert text == "The account shows currently a balance of 10.0"

BigDecimal minus = 4.0
text = "The account shows currently a balance of ${account - minus}"
assert text == "The account shows currently a balance of 6.0"

// Without the brackets to isolate the expression, this would result:
text = "The account shows currently a balance of $account - minus"
assert text == "The account shows currently a balance of 10.0 - minus"

BigDecimal tax = 0.15
text = "The account shows currently a balance of ${->account - account*tax}"
tax = 0.10

// The tax value was changed AFTER declaration of the GString. The expression 
// variables are bound only when the expression must actually be evaluated:
assert text == "The account shows currently a balance of 9.000"

trait FlyingAbility { /* declaration of a trait */
  String fly() { "I'm flying!" } /* declaration of a method inside a trait */
}

class Bird implements FlyingAbility {} /* Adds the trait FlyingAbility to the Bird class capabilities */
def bird = new Bird() /* instantiate a new Bird */
assert bird.fly() == "I'm flying!" /* the Bird class automatically gets the behavior of the FlyingAbility trait */

Notable examples of Groovy adoption include:

• Adaptavist ScriptRunner, embeds a Groovy implementation to automate and extend Atlassian tools, in use by more than 20000 organisations around the world.[34][35]
• Apache OFBiz, the open-source enterprise resource planning (ERP) system, uses Groovy.[36][37]
• Eucalyptus, a cloud management system, uses a significant amount of Groovy.
• Gradle is a popular build automation tool using Groovy.
• LinkedIn uses Groovy and Grails for some of their subsystems.[38]
• LogicMonitor, a cloud-based monitoring platform, uses Groovy in script-based data sources.[39]
• Jenkins, a platform for continuous integration. With version 2, Jenkins includes a Pipeline plugin that allows for build instructions to be written in Groovy.[40]
• Liferay, uses groovy in their kaleo workflow
• Sky.com uses Groovy and Grails to serve massive online media content.[41]
• SmartThings, an open platform for smart homes and the consumer Internet of Things, uses a security-oriented subset of Groovy[42]
• SoapUI provides Groovy as a language for webservice tests development.[43]
• Survata, a market research startup, uses Groovy and Grails.
• The European Patent Office (EPO) developed a dataflow programming language in Groovy "to leverage similarities in the processes for communicating with each individual country’s patent office, and transform them into a single, universal process."
• Though Groovy can be integrated into any JVM environment, the JBoss Seam framework provides Groovy, besides Java, as a development language, out of the box.[44]
• vCalc.com uses Groovy for all of the user defined mathematics in its math crowd-sourcing engine.[45]
• Wired.com uses Groovy and Grails for the Product Reviews standalone section of the website.[46]
• XWiki SAS uses Groovy as scripting language in their collaborative open-source product.[47]

Many integrated development environments (IDEs) and text editors support Groovy:

• Android Studio, IDE used for making Android apps
• Atom editor
• Eclipse, through Groovy-Eclipse
• Emacs, using the groovy-emacs-mode project's groovy-mode.
• IntelliJ IDEA, Community Edition, Grails/Griffon in the Ultimate Edition only
• JDeveloper, for use with Oracle ADF
• jEdit, an advanced text editor for the Java platform
• Kate, an advanced text editor for KDE supports Groovy and over 200 other file formats
• NetBeans, since version 6.5
• Notepad++, an advanced text editor for Microsoft Windows
• Sublime Text, a cross platform text editor
• TextMate
• Visual Studio Code
• UltraEdit, general purpose program editor

There is one alternative implementation of Groovy:

• Grooscript converts Groovy code to JavaScript code.[48] Although Grooscript has some limitations compared to Apache Groovy, it can use domain classes in both the server and the client.[49] Plugin support for Grails version 3.0 is provided, as well as online code conversions.[50]

• Comparison of programming languages
• Griffon (framework) – a desktop framework
• Project Zero
• Spock (testing framework)

• Official website
• Groovy at Curlie