Pretty printing Java classpaths using Ant's pathconvert task

Lance Hankins posted on Saturday about more readable classpaths using the <propertyregex> task. It jogged my memory back about 4 years when I was trying to solve the same problem. This was back in the days of Ant 1.4.1 and just before the existence of the optional Ant-Contrib package. Back then I was considered a bit of an Ant Meister by my colleagues as I managed to spend hours tweaking the smallest of things in my lovingly created Ant build environment searching for perfection...

So how did I solve this particular issue? A clue is in the title of this post, I used the <pathconvert> task, which is normally used to convert lists of files, directories, etc. and convert them to a different platform's style. So path separators using Windows ';' get converted to Unix ':', etc. But you can also use it to convert the path separators to something else, in my case a nicely formatted string for displaying in a printable form.

Here's the code:

<!-- get the source compile classpath in a printable form -->
<pathconvert pathsep="${line.separator}|   |-- "
             property="echo.path.compile"
             refid="path.classpath.compile">
</pathconvert>

The original classpath is referenced in 'path.classpath.compile', and the newly formatted classpath is saved in 'echo.path.compile'. The magic is the pathsep statement. This says that the path separator (the ';' or ':') is to be replaced with a new line (CR or CRLF depending on operating system) followed by some characters that make the listing look nice.

To display your pretty printed classpath just use:

<echo message="|-- compile classpath"/>
<echo message="|   |"/>
<echo message="|   |-- ${echo.path.compile}"/>

This gives the following output:

[echo] |-- compile classpath
[echo] |   |
[echo] |   |-- /tomcat/common/lib/jsp-api.jar
[echo] |   |-- /tomcat/common/lib/ant.jar
[echo] |   |-- /tomcat/common/lib/jmx.jar
[echo] |   |-- /tomcat/common/lib/commons-collections-3.1.jar
[echo] |   |-- /tomcat/common/lib/commons-dbcp-1.2.1.jar
[echo] |   |-- /tomcat/common/lib/commons-el.jar
[echo] |   |-- /tomcat/common/lib/commons-lang-2.1.jar
[echo] |   |-- /tomcat/common/lib/commons-pool-1.2.jar
[echo] |   |-- /tomcat/common/lib/tools.jar
[echo] |   |-- ...

So there you have it, nicely formatted classpaths using only standard Ant tasks.

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