Raise an error if a variable is not defined in Ant -

I need a user to define a variable in the compilation of time, I still have to decide whether this An environment variable or property ( ant -Dname = value ).

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First question: < / P>

If the variable is for environment-specific conditions outside the application, then it is an environment (OS) variable. Otherwise, make it a property, obviously, it does not fully answer your question, because what you still mean to decide (for your app or system) is to say that a variable environment Another specific guide is to ask yourself if you can apply one or more applications that depend on the different values ​​of the same variable, all of which are possibly deployed on the same system. Are being done. In such a case, we can not use an environment variable, the only way to go with the property-based variable.

For the second question:

Use the ant to undo Work if no condition or property is set. With an ant document on failed function, you can get an idea of ​​if you use a property-based variable:

  & lt; Unsuccessful & gt; & Lt; Condition & gt; & Lt; & Gt; No; & Lt; Isset property = "this danootexist" /> & Lt; Not / & gt; & Lt; / Condition & gt; & Lt; / Unsuccessful & gt;   
 If you decide to use an environment variable, you can          The function of taping in the environment (OS) is as they create qualities (pls refer to the example).  
 Hope this will be helpful.