Java Extreme Programming Cookbook

Defining a Classpath

Problem

You want to define a classpath and reuse it throughout a buildfile.

Solution

Use the <path> element to define the classpath along with a unique ID. Then refer to the classpath using the ID.

Discussion

Example 3-5 shows how to define a classpath and refer to it later from the javac task.

Example 3-5. Reusing a classpath

<?xml version="1.0" encoding="UTF-8"?>
<project name="Classpath Sample" default="compile" basedir=".">
  <!-- get an environment variable -->
  <property environment="env"/>
  <property name="tomcatHome" value="${env.TOMCAT_HOME}"/>

  <!-- define some directories -->
  <property name="dir.src" value="src"/>
  <property name="dir.build" value="build"/>
  <property name="dir.lib" value="lib"/>
  
  <!-- Define a classpath for use throughout the buildfile -->
  <path id="project.classpath">
    <pathelement location="${dir.src}"/>
    <!-- include Tomcat libraries -->
    <fileset dir="${tomcatHome}/common/lib">
      <include name="*.jar"/>
    </fileset>    
    <!-- include our own libraries -->
    <fileset dir="${dir.lib}">
      <include name="*.jar"/>
    </fileset>
  </path>
  
  <target name="clean">
    <delete dir="${dir.build}"/>
  </target>
  
  <target name="prepare">
    <mkdir dir="${dir.build}"/>
  </target>
  
  <target name="compile" depends="prepare">
    <!-- use <pathconvert> to convert the path into a property -->
    <pathconvert targetos="windows" property="windowsPath"
                 refid="project.classpath"/> <!-- now echo the path to the console --> <echo>Windows path = ${windowsPath}</echo> <!-- Here is how to use the classpath ...