练习上传下载时遇到的问题

• public class BaseServlet extends HttpServlet {
• @Override
• protected void service(HttpServletRequest req, HttpServletResponse res)
• throws ServletException, IOException {
• //页面的编码处理
• req.setCharacterEncoding("utf-8");
• res.setContentType("text/html;charset=utf-8");
• //获取页面要调用的method参数
• String methodName = req.getParameter("method");
• if(methodName==null || methodName.trim().isEmpty()){
• throw new RuntimeException("您未指定要调用的方法!");
• }
• //反射得到要调用的反射方法
• Class clazz = this.getClass();//所访问servlet的字节码文件对象
• Method method = null;
• try {
• method = clazz.getMethod(methodName, HttpServletRequest.class,HttpServletResponse.class);
• }
• catch (Exception e) {
• throw new RuntimeException("您要调用的方法"+methodName+"(HttpServletRequest,HttpServletResponse)不存在");
• }
• //执行方法
• try {
• String result = (String)method.invoke(this, req,res);
• if(result==null || result.trim().isEmpty()){
• return;
• }
• if(result.contains(":")){
• int addr = result.indexOf(":");
• String bef = result.substring(0,addr);
• String aft = result.substring(addr+1);
• if(bef.equalsIgnoreCase("r")){
• res.sendRedirect(req.getContextPath()+aft);
• }else if(bef.equalsIgnoreCase("f")){
• req.getRequestDispatcher(aft).forward(req, res);
• }else{
• throw new RuntimeException("您指定的操作有误");
• }
• }else{
• req.getRequestDispatcher(result).forward(req, res);
• }
• } catch (Exception e) {
• throw new RuntimeException("方法内部错误"+e);
• }
• }

• public class MyFileServlet extends BaseServlet {
• MyService service = new MyService();
• public String findAll(HttpServletRequest req,HttpServletResponse res){
• List<MyFile> list = service.findAll();
• req.setAttribute("list", list);
• return "f:/day22/list.jsp";
• }
• public String downLoad(HttpServletRequest req,HttpServletResponse res) {
• String fid = req.getParameter("fid");
• MyFile myfile = service.load(fid);
• try {
• //获取文件资源名称
• String path = req.getParameter("path");
• //解析路径
• String fname = myfile.getFilename();
• String name = myfile.getName();
• name = new String(name.getBytes("iso-8859-1"),"utf-8");
• //封装文件
• File file = new File(path,fname);
• if(!file.exists()){
• req.setAttribute("msg", "您要下载的资源不存在");
• return "f:/day22/msg.jsp";
• }
• int cnt = myfile.getCnt();
• /*
• 其中MyFile 类型的cnt属性是Integer的int cnt = myfile.getCnt();
• * myfile.setCnt(cnt+1);
• * service.edit(myfile);
• * 加入此句后会报出 方法内部错误
• * java.lang.reflect.
• * InvocationTargetException
• * 后来将接口参数由myfile对象换成两个
• * 需要的直接参数，而不是由myfile间接
• * 获取，问题解决，仔细思考之后发现其实是反射方法的
• 内部出了问题，也就是说baseservlet反射调用了我的这个
• 方法，而我这个方法内部有可能在处理或调用其他方法时出现问题
• * */
• service.edit(cnt+1,fid);
• name = new String(name.getBytes("GBK"),"iso-8859-1");
• res.addHeader("content-disposition", "attatchment;filename="+fname);
• IOUtils.copy(new FileInputStream(file), res.getOutputStream());
• } catch (Exception e) {
• throw new RuntimeException(e);
• }
• return null;
• }