How to check if a property has value in Ant

I have an Ant XML file which I use for build.

I have 3 properties. I want to break the build if these properties does not contain any value. Also I want to break the build if the value is empty.

How …

Ant: Class not found: javac1.8

I am trying to build a project using Ant in eclipse. I right-clicked on build.xml > Run As > Ant Build. However, I am getting the following error: