How to do String operations in Ant

I was trying to create an Ant based wizard to generate a Wicket quickstart project. So like the trend nowadays the script should prompt you for the project name at the start then *boom* – you get your Maven2 directory structure, pom.xml, web.xml, a couple of placeholder web-pages – just type mvn jetty:run and you are up and running.

I wanted the user to only enter the project-name: a lower-case string without spaces or special characters. Then I wanted the Wicket Application class to be generated as per tradition i.e. if your project short name is “test” the file should be “TestApplication.java”

But then it hit me – there is no way to do things like uppercase / lowercase string conversion in Ant! Yikes. I could make-do with a second prompt for the user to get the application class name, but hey, that’s so not-DRY, and I like an Ant challenge :)

One option was to use Beanshell – but I’m obsessed with getting things to work with a “clean” Ant install, without messing around with the classpath or ant-home. After being spoilt by Maven, I don’t like having orphan jar files lying around in the project directory structure either.

So I ended up doing this. Here is a small Java class that processes a command line argument and writes the result to a file:

import java.io.FileOutputStream;
import java.io.PrintWriter;

public class TitleCaser {

    public static void main(String[] args) throws Exception {
        FileOutputStream os = new FileOutputStream("target/temp.txt");
        PrintWriter out = new PrintWriter(os);
        String s = args[0];
        out.write(Character.toUpperCase(s.charAt(0)) + s.substring(1));
        out.close();
        os.close();
    }

}

This java file resides in an “etc” folder. And the start of the Ant script looks like this:

<javac srcdir="etc" includes="TitleCaser.java"/>        
<input message="Enter Project Name:" addproperty="project.name"/>
<java classpath="etc" classname="TitleCaser">
     <arg value="${project.name}"/>
</java>
<loadfile property="project.name.titleCase" srcFile="target/temp.txt"/> 

I know, I know, Ant is XML, it is a declarative language, I must be crazy etc. But I can think of all kinds of interesting things to do with this approach. There are various ways to load stuff into Ant from files, “loadfile” is just one of them. Think of the possibilities – you can generate Java code from Ant, “javac” it on the fly and work around all the Ant limitations like not having good control-flow support etc. Maybe you can even generate some XML and use that in a downstream target and tell your boss that your Ant build is SOA compliant…