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Flaka provides some very innovative features and syntactic sugar. This page will show how to tackle common ant problems with Flaka. Examples are taken from 'real-life' => production code, questions from stackoverflow.com, the Ant user list .. etc.

• Categories
• Properties
• Files / Directories
• Conditions

Categories

Properties

One of the most common question is how to overwrite or edit existing properties in ant.

Question : How do i overwrite an existing property ?
Solution : use the let task

Properties once set are immutable in ant by design.

<!-- set a new property -->
<fl:let>foo := 'bar'</fl:let>

<!-- overwrite an existing property or userproperty
     (those properties defined on the commandline via -Dfoo=bar ..) -->
<fl:let>foo ::= 'baz'</fl:let>

notice the double '::' in foo ::= 'baz'

Question : How do i extract a specific part from a csv separated property ?
Solution : use the split function with index

<project xmlns:fl="antlib:it.haefelinger.flaka">

  <property name="module.list" value="mod1,mod2,mod3,mod4,mod5"/>

  <target name="main">
    <!-- simple echo -->
    <fl:echo>xtractedvalue => #{split('${module.list}',',')[0]}</fl:echo>
    <!-- create property for further processing.. -->
    <fl:let>
      xtractedvalue := split('${module.list}',',')[0]
    </fl:let>
    <echo>$${xtractedvalue} => ${xtractedvalue}</echo>
  </target>

</project>

output :

 [fl:echo] xtractedvalue => mod1
 [echo] ${xtractedvalue} => mod1

a similar one :

Question : Given is an ant property which has value of the type 1.0.0.123
How to extract the value after the last dot, in this case that would be '123' ?
Solution : use the split function with index

<project xmlns:fl="antlib:it.haefelinger.flaka">

 <property name="foobar" value="1.0.0.123"/>

  <target name="main">
   <!-- simple echo -->
   <fl:echo>xtractedvalue => #{split('${foobar}','\.')[3]}</fl:echo>
   <!-- create property for further processing.. -->
   <fl:let>
    xtractedvalue := split('${foobar}','\.')[3]
   </fl:let>
   <echo>$${xtractedvalue} => ${xtractedvalue}</echo>
  </target>
</project>

output :

 [fl:echo] xtractedvalue => 123
 [echo] ${xtractedvalue} => 123

Question : For some reason i need to strip of the drive name of some property
${basedir} = "D:\some\directory\blah\blah"
${cwd} = some\directory\blah\blah"
Solution : use the replace function

<project xmlns:fl="antlib:it.haefelinger.flaka" name="World">
  <!-- simple echo -->
  <fl:echo>#{replace('${basedir}', '$1' , '.:\\\\(.+)' )}</fl:echo>
  <!-- set property -->
  <fl:let>cwd := replace('${basedir}', '$1' , '.:\\\\(.+)' )</fl:let>
</project>

Files / Directories

Question : After compiling my java sources how to run the corresponding classes ?
Solution : Iterate over the fileset which contains the java sources and use the replace function to call the corresponding class files.

This example shows also how to iterate over a fileset with the ant builtin ${toString:filesetid} property.

<project xmlns:fl="antlib:it.haefelinger.flaka">

  <property name="srcroot" value="path/to/srcrootdir"/>
  <property name="classroot" value="path/to/classrootdir"/>

  <!-- seek all classes with main method -->
  <fileset dir="${srcroot}" includes="**/*.java" id="mainclasses">
    <contains text="public static void main"/>
  </fileset>

  <!-- iterate over classes with main method and call
       corresponding classfile -->
  <fl:for var="file" in="split('${toString:mainclasses}', ';')">
    <fl:let>
      ; strip the '.java' extension
      file = replace(file, '', '.java')
      ; replace fileseparator with '.'
      ; when running on windows you have to use :
      ; replace(file, '\.', '${file.separator}${file.separator}')
      file = replace(file, '\.', '${file.separator}')
      </fl:let>
    <fl:echo>
      starting => #{file} in ${classroot}..
    </fl:echo>
    <java classname="#{file}">
      <classpath>
       <!--
         when using a fileset you'll get a
         java.util.zip.ZipException because you're
         referencing not jarfiles but classfiles
         therefore you've to use pathelement location
       -->
       <pathelement location="${classroot}"/>
      </classpath>
    </java>
  </fl:for>

</project>

Question : In ant, how can i check if a set of files (comma-separated list of paths) exists or not?
Solution : use

a) when with combined file function calls
or
b) use list function to iterate over the commaseparated pathentries

<project xmlns:fl="antlib:it.haefelinger.flaka">

  <!-- when you have a cvs property use split function
       to get your list to iterate over -->
  <property name="checkpath" value="/foo/bar,/foo/baz,/foo/bazz"/>
  <fl:for var="file" in="split('${checkpath}', ',')">
    <fl:fail message="#{file} does not exist !!" test="!file.tofile.exists"/>
  </fl:for>

  <!-- creating the list inline -->
  <fl:for var="file" in="list('/foo/bar','/foo/baz', '/foo/bazz')">
    <fl:fail message="#{file} does not exist !!" test="!file.tofile.exists"/
  </fl:for>

  <!-- using some if then else construct with choose -->
  <fl:choose>
    <fl:when test="file('/foo/bar').exists and file('/foo/baz' and file('/foo/bazz').exists">
      <!-- create property based on existence -->
      <fl:let>pathExist := true</fl:let>
      <!-- .. other nested tasks .. -->
    </fl:when>
    <fl:otherwise>
      <fl:let>pathExist := false</fl:let>
      <!-- .. other nested tasks .. -->
    </fl:otherwise>
  </fl:choose>

  <echo>${pathExist}</echo>

</project>

Conditions

Question : I would like to do something like this

<target name="clean" description="clean">
    <if>
        <available file="${build}" type="dir" />
        <then>
            <delete dir="${build}" />
        </then>
    </if>
</target>

Solution :

The standard way in vanilla ant would be something like

<target name="check">
  <condition property="delbuild">
    <available file="${build}" type="dir"/>
  </condition>
 </target>

 <target name="clean" depends="check" if="delbuild">
 <delete dir="${build}"/>
    <!-- .. -->
 </target>

with Flaka its straightforward

<fl:when test=" '${build}'.isdir ">
  <delete dir="${build}"/>
</fl:when>

Question : Is there any if then else construct in ant ?
Solution : Use choose/when/otherwise

<project xmlns:fl="antlib:it.haefelinger.flaka">
  <!-- some if/then/else construct -->
  <fl:choose>
    <!-- if -->
    <when test=" '${buildtype}' eq 'prod' ">
      <!-- then -->
      <echo>..starting ProductionBuild</echo>
    </when>
    <when test=" '${buildtype}' eq 'test' ">
      <!-- then -->
      <echo>..starting TestBuild</echo>
    </when>
    <!-- else -->
    <otherwise>
      <fl:unless test="has.property.dummybuild">
        <fail message="No valid buildtype !, found => '${buildtype}'"/>
      </fl:unless>
      <echo>.. is DummyBuild</echo>
    </otherwise>
  </fl:choose>
</project>

output with ant -f build.xml -Dbuildtype=prod or
ant -f build.xml -Dbuildtype=prod -Ddummybuild=whatever

[echo] ..starting ProductionBuild

output with typo => ant - build.xml -Dbuildtype=testt

BUILD FAILED
/home/rosebud/workspace/AntTest/build.xml:21: No valid buildtype !, found => 'testt'

output with ant -f build.xml -Ddummybuild=whatever

[echo] .. is DummyBuild