[string] Replacing characters in Ant property

Here's a more generalized version of Uwe Schindler's answer:

You can use a macrodef to create a custom task.

<macrodef name="replaceproperty" taskname="@{taskname}">
    <attribute name="src" />
    <attribute name="dest" default="" />
    <attribute name="replace" default="" />
    <attribute name="with" default="" />
    <sequential>
        <loadresource property="@{dest}">
            <propertyresource name="@{src}" />
            <filterchain>
                <tokenfilter>
                    <filetokenizer/>
                    <replacestring from="@{replace}" to="@{with}"/>
                </tokenfilter>
            </filterchain>
        </loadresource>
    </sequential>
</macrodef>

you can use this as follows:

<replaceproperty src="property1" dest="property2" replace=" " with="_"/>

this will be pretty useful if you are doing this multiple times