Servlet 起航 文件上传 中文文件名下载

 @WebServlet(name = "ticketServlet",urlPatterns = {"/tickets"},loadOnStartup = 1)
 @MultipartConfig(fileSizeThreshold = 5242880,
 maxFileSize = 20971520L,//20MB
 maxRequestSize = 41943040L//40MB
 )
 public class TicketServlet extends HttpServlet{
     //线程可见性
     private volatile int TICKET_ID_SEQUENCE = 1;
     private Map<Integer,Ticket> ticketDatabase = new LinkedHashMap<>();

     @Override
     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
        //使用请求参数做了一个菜单
         String action = req.getParameter("action");
         if (action == null){
             action = "list";//默认ticket列表
         }
         switch (action){
             case "create":
                 this.showTicketForm(resp);//展示表单
                 break;
             case "view":
                 this.viewTicket(req,resp);//具体一张
                 break;
             case  "download":
                 this.downloadAttachment(req,resp);//下载附件
                 break;
             default:
                 this.listTickets(resp);//展示ticket
                 break;
         }
     }

     @Override
     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
         String action = req.getParameter("action");
         if(action == null){
             action = "list";
         }
         switch (action){
             case "create":
                 this.createTicket(req,resp);//表单提交实际创建方法
                 break;
             case "list":
             default:
                 resp.sendRedirect("tickets");//重定向 get
                 break;

         }

     }

     private void listTickets(HttpServletResponse response) throws IOException {
         PrintWriter writer = this.writeHeader(response);

         writer.append("<h2>Tickets</h2>\r\n");
         //createTicket入口 先展示一个表单
         writer.append("<a href=\"tickets?action=create\">Create Ticket")
                 .append("</a><br/><br/>\r\n");

         if(this.ticketDatabase.size() == 0)
             writer.append("<i>There are no tickets in the system.</i>\r\n");
         else
         {
             for(int id : this.ticketDatabase.keySet())
             {
                 String idString = Integer.toString(id);
                 Ticket ticket = this.ticketDatabase.get(id);
                 writer.append("Ticket #").append(idString)
                         .append(": <a href=\"tickets?action=view&ticketId=")
                         .append(idString).append("\">").append(ticket.getSubject())
                         .append("</a> (customer: ").append(ticket.getCustomerName())
                         .append(")<br/>\r\n");
             }
         }

         this.writeFooter(writer);
     }

     private void viewTicket(HttpServletRequest request, HttpServletResponse response) throws IOException {
         //从ticket列表进入某张ticket所需要id
         String idString = request.getParameter("ticketId");
         Ticket ticket = this.getTicket(idString, response);
         if(ticket == null)
             return;

         PrintWriter writer = this.writeHeader(response);

         writer.append("<h2>Ticket #").append(idString)
                 .append(": ").append(ticket.getSubject()).append("</h2>\r\n");
         writer.append("<i>Customer Name - ").append(ticket.getCustomerName())
                 .append("</i><br/><br/>\r\n");
         writer.append(ticket.getBody()).append("<br/><br/>\r\n");

         if(ticket.getNumberOfAttachments() > 0)
         {
             writer.append("Attachments: ");
             int i = 0;
             for(Attachment attachment : ticket.getAttachments())
             {
                 if(i++ > 0)
                     writer.append(", ");
                 writer.append("<a href=\"tickets?action=download&ticketId=")
                         .append(idString).append("&attachment=")
                         .append(attachment.getName()).append("\">")
                         .append(attachment.getName()).append("</a>");
             }
             writer.append("<br/><br/>\r\n");
         }

         writer.append("<a href=\"tickets\">Return to list tickets</a>\r\n");

         this.writeFooter(writer);
     }

     private Ticket getTicket(String id, HttpServletResponse response) throws IOException {
         //id.len == ''  一般合法性检查  有没有
         if (id == null || id.length()==0){
             response.sendRedirect("tickets");
             return null;
         }
         try {
             Ticket ticket = this.ticketDatabase.get(Integer.parseInt(id));
             if (ticket == null) {
                 response.sendRedirect("tickets");
                 return null;
             }
             return ticket;
         }catch (Exception e){
             response.sendRedirect("tickets");
             return null;
         }
     }

     private void showTicketForm(HttpServletResponse resp) throws IOException {
         PrintWriter writer = this.writeHeader(resp);
         writer.append("<h2>Create a Ticket</h2>\r\n");
         writer.append("<form method=\"POST\" action=\"tickets\" ")
                 .append("enctype=\"multipart/form-data\">\r\n");//编码类型multipart/form-data
         writer.append("<input type=\"hidden\" name=\"action\" ")//隐藏域提交 action value = create
                 .append("value=\"create\"/>\r\n");
         writer.append("Your Name<br/>\r\n");
         writer.append("<input type=\"text\" name=\"customerName\"/><br/><br/>\r\n");
         writer.append("Subject<br/>\r\n");
         writer.append("<input type=\"text\" name=\"subject\"/><br/><br/>\r\n");
         writer.append("Body<br/>\r\n");
         writer.append("<textarea name=\"body\" rows=\"5\" cols=\"30\">")
                 .append("</textarea><br/><br/>\r\n");
         writer.append("<b>Attachments</b><br/>\r\n");
         writer.append("<input type=\"file\" name=\"file1\"/><br/><br/>\r\n");
         writer.append("<input type=\"submit\" value=\"Submit\"/>\r\n");
         writer.append("</form>\r\n");

         this.writeFooter(writer);
     }

     private void downloadAttachment(HttpServletRequest request, HttpServletResponse response) throws IOException {
        //下载某一个attachment
         String idString = request.getParameter("ticketId");
         Ticket ticket = this.getTicket(idString, response);
         if(ticket == null)
             return;

         String name = request.getParameter("attachment");
         if(name == null)
         {
             response.sendRedirect("tickets?action=view&ticketId=" + idString);
             return;
         }

         Attachment attachment = ticket.getAttachment(name);
         if(attachment == null)
         {
             response.sendRedirect("tickets?action=view&ticketId=" + idString);
             return;
         }
         //header 内容位置   文件名
         response.setHeader("Content-Disposition",
                 "attachment; filename=" + attachment.getName());

         response.setContentType("application/octet-stream");
         //流
         ServletOutputStream stream = response.getOutputStream();
         stream.write(attachment.getContents());
     }

     private void createTicket(HttpServletRequest req, HttpServletResponse resp) throws IOException, ServletException {
         Ticket ticket = new Ticket();
         ticket.setCustomerName(req.getParameter("customerName"));
         ticket.setSubject(req.getParameter("subject"));
         ticket.setBody(req.getParameter("body"));

         Part filePart = req.getPart("file1");
         if (filePart!=null){
             Attachment attachment = this.processAttachment(filePart);
             if (attachment!=null)
                 ticket.addAttachment(attachment);
         }
         int id;
         synchronized (this){
             id = this.TICKET_ID_SEQUENCE++;
             this.ticketDatabase.put(id,ticket);
         }
         resp.sendRedirect("tickets?action=view&ticketId="+id);
     }

     private Attachment processAttachment(Part filePart) throws IOException {
         InputStream inputStream = filePart.getInputStream();//用户输入流
         ByteArrayOutputStream outputStream = new ByteArrayOutputStream();//写入attachment做准备

         int read;
         final byte[] bytes  = new byte[1024];//buffer
         while((read=inputStream.read(bytes))!=-1){//有多少
             outputStream.write(bytes,0,read);//写多少
         }

         Attachment attachment = new Attachment();
         attachment.setName(filePart.getSubmittedFileName());
         attachment.setContents(outputStream.toByteArray());

         return attachment;
     }

     private PrintWriter writeHeader(HttpServletResponse response)
             throws IOException
     {
         response.setContentType("text/html");
         response.setCharacterEncoding("UTF-8");

         PrintWriter writer = response.getWriter();
         writer.append("<!DOCTYPE html>\r\n")
                 .append("<html>\r\n")
                 .append("    <head>\r\n")
                 .append("        <title>Customer Support</title>\r\n")
                 .append("    </head>\r\n")
                 .append("    <body>\r\n");

         return writer;
     }

     private void writeFooter(PrintWriter writer)
     {
         writer.append("    </body>\r\n").append("</html>\r\n");
     }

 }

【文件下载细节】

 //header 内容位置   文件名
 response.setHeader("Content-Disposition",
         "attachment; filename=" +
                 new String(attachment.getName().getBytes("UTF-8"),"ISO8859-1"));//浏览器支持的编码是ISO8859-1
 response.setContentType("application/octet-stream");
 //流
 ServletOutputStream stream = response.getOutputStream();
 stream.write(attachment.getContents());