My code works just fine.  Then I added some extra features.  And everything is not working.  So I decide to revert back, but I got the error

Errors during build.
  Errors running builder 'Integrated External Tool Builder' on project 'csns'.
  The builder launch configuration could not be found.

What is the problem?

And at the same time, the pgsql does not work either.

Error connecting to the server: server closed the connectin unexpectedly

This probably means the server terminated abnormally before or while processing the request.

And I checked my source code, it seems that eclips cannot find the lib file for thins like:

org.apache

org.springframework

and so on

Problem solved, I need to restart my computer and everyting works fine.

Except that some of code is missing during the whole process.  So I need to rewrite them again.