Mysterious Eclipse JSP Validation Errors

Question

Eclipse (Helios) occasionally marks valid looking JSP content as having errors. It seems like it often breaks when I use the tag. For example, in a JSP with just th

Answer 1

I also see the same problem during I shift to Maven (with m2e), get error like "javax.servlet.http cannot be resolved" and some Spring tags undefined warning. finally I find it's because java version (v1.6) in my build configuration is not same as in facets configuration (v1.7). after change v1.7 to v1.6 the problem disappear.