Jar, War and Ear files are essentially the archived files. There are no structural differences among the three types, though these are intended for different purposes.
Jar: Jar files (Java Archive file : .jar extension) stores of Java classes, resources, auxiliary files, etc. Java source files are compiled and then distributed in jar format.
War files (Web Archive File : .war extension) are intended to contain complete Web applications. A Web Application is a collection of files, classes, resources, .jar files that can be packaged and accessed as one servlet context. Usually, sample web applications are distributed using war format.
Ear files (Enterprise Archive file : .ear extension) are intended to contain complete Enterprise applications. In this context, an enterprise application is defined as a collection of .jar files, resources, classes, and multiple Web applications.
All three types of files can be generated using Ant.
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