在命令行中覆盖ANT_HOME属性

Question

I am writing a Java RCP application, where I input a file path from user for ANT_HOME and then evaluate the version for validation. However, when I set ANT_HOME property as system property, the evaluation fails because the ant.bat script contains

rem %~dp0 is expanded pathname of the current script under NT
set DEFAULT_ANT_HOME=%~dp0..

if "%ANT_HOME%"=="" set ANT_HOME=%DEFAULT_ANT_HOME%

I do not need to update my ANT_HOME but need to override the value so that path entered by the user can be evaluated for a valid/invalid ant version for my application.

The issue occurs even when I am using my command line. See below screenshot.

C:\Users\tunnikrishnan>echo %ANT_HOME%
E:\tools\apache-ant-1.8.4

C:\Users\tunnikrishnan>E:\tools\apache-ant-1.6.5\bin\ant.bat -version
Apache Ant(TM) version 1.8.4 compiled on May 22 2012
C:\Users\tunnikrishnan>

Can somebody guide me how can I get to workaround on this?

Answer 1

Change the environment variables of the ProcessBuilder instance.

ProcessBuilder pb = new ProcessBuilder("myCommand", "myArg1", "myArg2");
Map<String, String> env = pb.environment();
env.put("ANT_HOME", getUserAntHome());
pb.redirectErrorStream(true);
Process p = pb.start();

where getUserAntHome() gets value from user input.