As a reason of this problem, some code is broken or undefined.You may see an error in a java class such as "The type javax.servlet.http.HttpSession cannot be resolved. It is indirectly referenced from required .class files". you shuold download " javax.servlet.jar" as mentioned before. Then configure your project build path, add the javax.servlet.jar as an external jar.I hope it fixes the problem.At least it worked for me.