Eclipse: "SDK directory '/myproject/war' does not exist"

Earlier today my Eclipse started to behave strangely. When I change the Google App Engine SDK of my project in Properties → Google → App Engine and click on OK, a dialog appears saying:

'Updating /myproject/war/WEB-INF/lib with jars from /home/dominik/.eclipse/org.eclipse.platform_3.7.0_1543616141/plugins/com.google.appengine.eclipse.sdkbundle_1.5.2.r37v201107211953/appengine-java-sdk-1.5.2 - 1.5.2' has encountered a problem.

SDK directory '/myproject/war' does not exist

If I click on Details >> it says:

SDK directory '/myproject/war' does not exist

There is no error on stdout. I don't know why eclipse is looking for /myproject/war. It should be /home/dominik/workspace/myproject/war. In Properties → Resource I have:

Path: /myproject

Type: Project

Location: /home/dominik/workspace/myproject

Deleting the .eclipse folder and reinstalling the plugin didn't help. The log (workspace/.metadata/.log) has the following lines:

!ENTRY com.google.appengine.eclipse.core 4 0 2011-08-06 18:59:33.999

!MESSAGE SDK directory '/myproject/war' does not exist

I posted a more detailed stack trace on the App Engine issue tracker:开发者_Go百科 http://code.google.com/p/googleappengine/issues/detail?id=5518

A Google search found one thread with the same problem but no solution: http://forum.springsource.org/showthread.php?91089-Spring-3.0.2-JPA-2.0-Hibernate-3.5.0

I still don't know what caused the problem, but creating a new project and manually moving all the project files into the new folder solved it.

A slightly easier solution to the same problem; delete the project inside Eclipse and re-import it.