Eclipse Template Proposals (aka auto completion) not working

recently the proposals (Ctrl+Space) for Eclipse/Java stopped working, as suggested in the wiki 开发者_运维百科I looked at the Preferences of Content Assist for Java, but all options are checked and still not working, any idea?

EDIT: One error is shown while trying to display proposals: Project facet grails.app has not been defined. It is used in plugin com.springsource.sts.server.tc.core.

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Somehow the references to the JDK where broken, so no completions could be made!

UPDATE: Solved by going to Window -> Preferences -> Installed JREs and changing the JDK folder to the right one.