Importing war file into eclipse and build path problem

I am facing some weird problem when importing .war file into eclipse.

The problem is, the build folder does not contain any necessary class folder. So when I try to set the build path, eclipse reports "Error while adding to build path. Reason: cannot nest output folder 'projectName/build/class' inside 'projectName/build'. From what I understand, 'build' folder is what classes get collected(as build version) right?

I tried to ignore build path and just export .war file into tomcat s开发者_JS百科erver, but somehow servlet file keeps showing old code, which I changed in eclipse. So, I am thinking without proper build folder, exported .war will not contain modified servlect code.( I am sorry if this doesn't sound clear)

What can I do to fix this problem? I already tried to create a whole new workspace and restarted eclipse several times and it didn't solve the problem.

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I figured it out. It was mistake to interpret build folder as what I described in the question. Build folder cannot be nested.