code: public String getServletPackageName() {
          if (isTagFile()) {
              String className = tagInfo.getTagClassName();
              int lastIndex = className.lastIndexOf('.');
              String pkgName = "";
              if (lastIndex != -1) {
                  pkgName = className.substring(0, lastIndex);
              }
              return pkgName;
          } else {
              String dPackageName = getDerivedPackageName();
              if (dPackageName.length() == 0) {
                  return basePackageName;
              }
              return basePackageName + '.' + getDerivedPackageName();
          }
      }
docs: Package name for the generated class is make up of the base package
  name, which is user settable, and the derived package name.  The
  derived package name directly mirrors the file hierarchy of the JSP page.
  @return the package name