Replacing characters in Ant property

Question

Is there a simple way of taking the value of a property and then copy it to another property with certain characters replaced?

Say propA=This is a value. I want to replace all the spaces in it into underscores, resulting in propB=This_is_a_value.

Answer 1

Here is the solution without scripting and no external jars like ant-conrib:

The trick is to use ANT's resources:

• There is one resource type called "propertyresource" which is like a source file, but provides an stream from the string value of this resource. So you can load it and use it in any task like "copy" that accepts files
• There is also the task "loadresource" that can load any resource to a property (e.g., a file), but this one could also load our propertyresource. This task allows for filtering the input by applying some token transformations. Finally the following will do what you want:

<loadresource property="propB">
  <propertyresource name="propA"/>
  <filterchain>
    <tokenfilter>
      <filetokenizer/>
      <replacestring from=" " to="_"/>
    </tokenfilter>
  </filterchain>
</loadresource>

This one will replace all " " in propA by "_" and place the result in propB. "filetokenizer" treats the whole input stream (our property) as one token and appies the string replacement on it.

You can do other fancy transformations using other tokenfilters: http://ant.apache.org/manual/Types/filterchain.html

Answer 2

Use the propertyregex task from Ant Contrib.

I think you want:

<propertyregex property="propB"
               input="${propA}"
               regexp=" "
               replace="_"
               global="true" />

Unfortunately the examples given aren't terribly clear, but it's worth trying that. You should also check what happens if there aren't any underscores - you may need to use the defaultValue option as well.

Answer 3

Two possibilities :

via script task and builtin javascript engine (if using jdk >= 1.6)

<project>

 <property name="propA" value="This is a value"/>

 <script language="javascript">
  project.setProperty('propB', project.getProperty('propA').
   replace(" ", "_"));
 </script>
 <echo>$${propB} => ${propB}</echo>

</project>

or using Ant addon Flaka

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

 <property name="propA" value="This is a value"/>

 <fl:let> propB := replace('${propA}', '_', ' ')</fl:let>

 <echo>$${propB} => ${propB}</echo>

</project>

to overwrite exisiting property propA simply replace propB with propA

Answer 4

Adding an answer more complete example over a previous answer

<property name="propB_" value="${propA}"/>
<loadresource property="propB">
  <propertyresource name="propB_" />
  <filterchain>
    <tokenfilter>
      <replaceregex pattern="\." replace="/" flags="g"/>
    </tokenfilter>
  </filterchain>
</loadresource>

Answer 5

Or... You can also to try Your Own Task

JAVA CODE:

class CustomString extends Task{

private String type, string, before, after, returnValue;

public void execute() {
    if (getType().equals("replace")) {
        replace(getString(), getBefore(), getAfter());
    }
}

private void replace(String str, String a, String b){
    String results = str.replace(a, b);
    Project project = getProject();
    project.setProperty(getReturnValue(), results);
}

..all getter and setter..

ANT SCRIPT

...
<project name="ant-test" default="build">

<target name="build" depends="compile, run"/>

<target name="clean">
    <delete dir="build" />
</target>

<target name="compile" depends="clean">
    <mkdir dir="build/classes"/>
    <javac srcdir="src" destdir="build/classes" includeantruntime="true"/>
</target>

<target name="declare" depends="compile">
    <taskdef name="string" classname="CustomString" classpath="build/classes" />
</target>

<!-- Replacing characters in Ant property -->
<target name="run" depends="declare">
    <property name="propA" value="This is a value"/>
    <echo message="propA=${propA}" />
    <string type="replace" string="${propA}" before=" " after="_" returnvalue="propB"/>
    <echo message="propB=${propB}" />
</target>

CONSOLE:

run:
     [echo] propA=This is a value
     [echo] propB=This_is_a_value

Answer 6

Just an FYI for answer Replacing characters in Ant property - if you are trying to use this inside of a maven execution, you can't reference maven variables directly. You will need something like this:

...
<target>
<property name="propATemp" value="${propA}"/>
    <loadresource property="propB">
    <propertyresource name="propATemp" />
...