//struts.xml <struts> <constant name="struts.devMode" value="true" /> ..... </struts>

i) Check where struts.xml is defined - Path where the file exists. In netbeans, easy way to do this to add the struts.xml file to package folder. ii) Check if the correct namespace is added in the struts.xml iii) Check if the package name is given correctly for the class in execution.