我建议你在所谓的DEV和PROD你的的build.xml 文件中定义目标然后调用Ant为：

 蚂蚁DEV
 

或

 蚂蚁PROD
 

如果你想坚持与您当前使用的系统属性来选择目标的方法，然后@克罗克的答案似乎是要走的路。 （但我没有看到任何的优势，这种做法虽然。）

I'm recently assigned a task to make ant be able to build war packages for different environments. I'm almost done except one feature.

The ant accepts an env parameter by like -Denv=DEV, and use different configuration files to make the war package. But the default target is start which will build, deploy and start the tomcat. I don't want ant to deploy the war neither start the server when I pass in the -Denv=PROD arg. I only want ant to build the ROOT.war. It's enough.

I know I can just type one more word to achieve this goal, but you know we are all lazy. :D

Does anyone know how to change the default target according to the command line argument? My requirements are as below:

1. ant -Denv=DEV will build, deploy, and start the server
2. ant -Denv=PROD will only build the ROOT.war

I suggest that you define targets in your build.xml file called "DEV" and "PROD" and then invoke Ant as:

ant DEV

or

ant PROD

If you want to stick with your current approach of using a system property to select the target, then @krock's answer seems to be the way to go. (But I don't see any advantage in that approach though.)