A number of other things can generate it, and most of them are clerical errors: misspellings, wrong form bean names, wrong action attribute in your <html:form> tag.
If you'd like help in debuggin it, post the following:
1-The relevant portions of your struts-config.xml file. 2-The relevant portions of your jsp, including the <html:form> tag and all references to the fname property. 3-The ActionForm bean.
I would like to have the .java for struts for debugging purposes into my project. Where can I get that?
Just go to the Struts home page and select the download link. Find the download page for the version of Struts you're using. When you see a page that allows you to select between binaries and source, select source.