Question: When I try to create a WAR file ()in eclipse by Right Click on Project--> Export--> War File, 
the window indicating WAR file creation exits without notice. Is it normal? If not, can I get some suggestions why am I getting this error?

Answer: 
You need to change type of eclipse java project into web project.

Best way is to create a new Web project and copy data from old project into web project.

In my case, I did the following steps

1. Old Project\WEB-INF\src to New Web Project\src
2. Old Project\WEB-INF\lib to New Web Project\lib

Otherwise if you want to do steps manually then please refer the below link
["Module name is invalid" when exporting an existing eclipse project to a war file](https://stackoverflow.com/questions/6129780/module-name-is-invalid-when-exporting-an-existing-eclipse-project-to-a-war-fil)
Sometimes wizard error can appear due to insufficient storage in C: drive.
Tried creating the same after clearing Temp storage and it works for me.