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)
It's possible that a `war` file with the same file name already exists. If that's the case then be sure to check the "overwrite existing files" checkbox in the export wizard.

If it is not the problem, for sure there is some bug in your Eclipse IDE.
The reason is you supposedly update the (WTP Patches 3.4.0) that causes the eclipse an error when exporting the `war` file.

I encountered this problem once and the solution is to install a new Eclipse IDE.