How to read the Class-Path from a JAR in Ant?

Question

The Class-Path of a JAR is written in the Manifest file in the JAR. The following Bash code reads the Class-Path from a JAR, if it does not exceed the 72 char limit:

unzip -c "$1" META-INF/MANIFEST.MF |
sed -n 's/^Class-Path: \(.\+\)$/\1/p' |
tr -d '\r'

Right now I am calling the code with exec in Ant but I would like to remove all execs.

How to do the same in Ant without using unzip, sed and tr?

Answer 1

You may want to try adding the following (in the beginning of your build.xml file where properties are defined) which puts the short Class-Path in property classpath:

<loadresource property="classpath">
    <zipentry zipfile="demo.jar" name="META-INF/MANIFEST.MF"/>
    <filterchain>
        <tokenfilter>
            <containsregex pattern="^Class-Path: (.+)$" flags="i"/>
            <replaceregex pattern="^Class-Path: (.+)$" replace="\1" flags="i"/>
        </tokenfilter>
        <tokenfilter><!-- get rid of trailing line separator -->
            <filetokenizer/>
            <replaceregex pattern="(\r?\n)+" replace="" flags="m"/>
        </tokenfilter>
    </filterchain>
</loadresource>

Edit: If you put the following before the tokenfilter above, then it should also work for longer values of Class-Path (by first joining split lines):

<tokenfilter>
    <filetokenizer/>
    <replaceregex pattern="\r?\n (.+)$" replace="\1" flags="m"/>
</tokenfilter>