====== Groovy ==
===== Getting Help ==
  * Indexes: [[groovy>Documentation|Groovy Documentation Home]] - [[ibm>views/java/libraryview.jsp?search_by=practically+groovy|IBM Practically Groovy]]
  * Tutorials:
  * APIs: [[groovy>gapi/|Groovy API]] FIXME add description - [[groovy>groovy-jdk]] Groovy methods added to standard Java SE classes

===== Install ==

[[groovy>Download]] the binary and unpack it to ''/usr/local'' and make a symlink: ''/usr/local# ln -s groovy-1.6.5 groovy''

[[groovy>Installing+Groovy|Add]] groovy bin directory to your invironment variables:
<code bash>
# /etc/profile.d/jdk.sh
...
export GROOVY_HOME=/usr/local/groovy
export PATH="$PATH:$GROOVY_HOME/bin"
</code>

===== Tools ==

[[groovy>Groovy+Console|groovyConsole]] is a GUI app for evaluating Groovy scripts and [[groovy>Groovy+Shell|groovysh]] is an interactiove CLI app for evaluating Groovy expressions.

[[groovy>Groovy+CLI|groovy]] ist the interpreter for Groovy scripts (see below) and ''groovyc'' is the compiler which compiles Groovy scripts to java classes (see below)

===== Script Files ==
==== Shebang ==

<code groovy>
#!/usr/bin/env groovy
println "Hallo Sandy!"
</code>

==== Command Line Arguments ==

<code groovy>
// file: test.groovy
println args[0]+ ' '+ args[1]+ ' '+ args[2]+ ' '+ args.length
</code>

Invoking the script with ''test.groovy one two three'' prints ''one two three 3''.

See also [[groovy>Groovy+CLI]]

==== Stdin stdout stderr ==

FIXME ''System.in.text''

==== Behind the Scenes ==

A script automatically creates a class which has the same name as the filename of the script:

<code groovy>
#!/usr/bin/env groovy
// Filname: groovytest
println this.class      // prints: class groovytest
println getClass()      // prints: class groovytest
println this.getClass() // prints: class groovytest
</code>

The first version is a [[javaref>api/java/lang/Class.html|class literal]] and seems to be a shortcut for calling getClass().

''println'' seems to call implizitely ''toString()'' on any object. (This is the same as ''System.out.println()'' in standard java.):

<code groovy>
println this.class            // prints: class groovytest
println this.class.toString() // prints: class groovytest
</code>

The parent class of the autogenerated script class is ''[[groovy>gapi/groovy/lang/Script.html|groovy.lang.Script]]'':
<code groovy>
println this.class.getSuperclass() // prints: groovy.lang.Script
</code>

''println()'' is a method of the autogenerated script class (inherited from ''groovy.lang.Script''). It can be called without ''this.'' and braces. This seems to be added automatically, because the following call prints: ''...Exception: No signature of method: groovytest.println() is applicable for argument types: (java.lang.Integer, java.lang.Integer)...''

<code groovy>
#!/usr/bin/env groovy
// Filename: groovytest
println 0,0
</code>

===== Compile Groovy Scripts ==

Groovy scripts can be [[groovy>Compiling+Groovy|compiled]] to java class files with ''groovyc''. In order to run those classes with the normal ''java'' command, you either have to [[groovy>Running|include]] ''/usr/local/groovy/embeddable/goovy-all-1.6.5.jar'' to the ''CLASSPATH'' variable or better :?:((to be tested!)) make a symlink in the [[javatut>ext/basics/install.html|Java Installed Extensions]] directory:

  cd /usr/lib/java/jre/lib/ext
  ln -s /usr/local/groovy/embeddable/goovy-all-1.6.5.jar

Note that this would have to be done on every system which wants to run a compiled script. Therefore it is better to create a jar file wich already includes the necessary depcendencies. This is described [[groovy>WrappingGroovyScript|here]].

===== Java Web Start ==

FIXME Add Groovy specific infos about Java Web Start here.

See also [[java#java_web_start|generic Java Web Start]]

===== Apache Pivot ==

FIXME Add Groovy specific infos about Pivot here. http://www.ibm.com/developerworks/xml/tutorials/x-pivottut/

See also generic [[Apache Pivot]]

==== Java Web Start ==

FIXME Add Groovy / Pivot specific infos about Java Web Start here.

See also [[Apache Pivot#java_web_start|general pivot specific things about Java Web Start]]

===== Dynamic Typing ==

''def'' is a replacement for a type name e.g. in method signatures. It is used to indicate that you don't care about the type. You can omit ''def'' in global variables of a script:

<code groovy>
def seven=7;   println "seven.class: "+ seven.class // -> class java.lang.Integer 
int eight=8;   println "eight.class: "+ eight.class // -> class java.lang.Integer
nine=9;        println "nine.class: " + nine.class  // -> class java.lang.Integer

seven="seven"; println "seven.class: "+ seven.class // -> class java.lang.String
//eight="eight"; println "eight.class: "+ eight.class // GroovyCastException!!!
nine="nine";   println "nine.class: " + nine.class  // -> class java.lang.String
</code>

===== Collections: Lists, Ranges and Maps ==
==== Lists ==

<code groovy>
#!/usr/bin/env groovy
myList = [1976, 1969] // create a list
myList << 2010        // append something to the end
println myList        // => [1976, 1969, 2010]
println myList[2]     // => 2010
println myList[3]     // => null
println myList.size   // => 3
</code>

Iterate over the list by calling the ''each()'' method on the list and pass in a closure:

<code groovy>
myList.each{ print "$it " }                    // => 1976 1969 2010
myList.eachWithIndex{ v, k -> print "$k:$v " } // => 0:1976 1:1969 2:2010
</code>

Each list [[groovy>Collections|creates]] an implementation of [[javaref>api/java/util/List.html|java.util.List]]. Hence the complete API of List is available:

<code groovy>
println myList.class  // => class java.util.ArrayList
println myList.get(0) // => 1976
println myList.size() // => 2
</code>

More on lists: [[groovy>JN1015-Collections|usage examples]], [[groovy>groovy-jdk/java/util/List.html|added methods to the standard List interface]], [[ibm>java/library/j-pg04149.html|Reaching for each]]

==== Maps ==

<code groovy>
myMap = ["Sandy":1976, "Becki":1969]
println myMap.Sandy        // => 1976
println myMap.get("Sandy") // => 1976
println myMap.class        // => null (default getter is overwritten !!!)
println myMap.getClass()   // => class java.util.LinkedHashMap
myMap.Junior="2010?"       // Add a new value
myMap.each{ print "$it " }              // => Sandy=1976 Becki=1969 Junior=2010?
myMap.each{ print "$it.key=$it.value "} // => Sandy=1976 Becki=1969 Junior=2010?
myMap.each{ k, v -> print "$k=$v " }    // => Sandy=1976 Becki=1969 Junior=2010?
</code>

More on maps: [[ibm>java/library/j-pg04149.html|Reaching for each]], [[groovy>JN1035-Maps|Maps]]

===== Unsorted ==

  * Interfaces can be [[groovy>Groovy+way+to+implement+interfaces|implemted using closures and maps]]
  * ''.sort()'' is a method added to [[groovy>groovy-jdk/java/util/Collection.html|Collection]] by Groovy
  * Everything can be [[ibm>java/library/j-pg04149.html|traversed]] using ''each''
  * Getters and setters are [[ibm>java/library/j-pg02179.html#N10203|autogenerated]]
  * ''def'' is used for dynamically typed variables. See [[groovy>Scoping+and+the+Semantics+of+"def"]] -> What is this "def" I heard of?

===== Open Questions / To do ==

  * Grails: http://grails.org/doc/latest/guide/17.%20Deployment.html http://grails.org/Deployment
  * [[http://www.ibm.com/developerworks/java/library/j-pg03155/|GroovyServer Pages]]
  * [[http://docs.codehaus.org/display/GROOVY/Extended+Guide+to+Method+Signatures|Named arguments]] are possible. Are they useful?
  * Final classes can be [[ibm>java/library/j-pg06239.html|extended]]