Apache Ant difference - exec vs apply

Can anyone tell me the开发者_JAVA技巧 difference between <exec> and <apply> in Apache Ant?

The main difference is that apply works for a resource collection - fileset, dirset and the like - so you can, for example, run a script once for each member of a fileset. exec doesn't operate on a fileset; each instance of the task only runs a single external program. Otherwise the tasks are quite similar.