第一步：创建Servlet
第二步：写代码
public class FielDownLoad extends HttpServlet {
/*** Constructor of the object.*/public FielDownLoad() { super();}
/*** Destruction of the servlet. <br>*/public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here}
/*** The doGet method of the servlet. <br>** This method is called when a form has its tag value method equals to get.* * @param request the request send by the client to the server* @param response the response send by the server to the client* @throws ServletException if an error occurred* @throws IOException if an error occurred*/public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);}
/*** The doPost method of the servlet. <br>** This method is called when a form has its tag value method equals to post.* * @param request the request send by the client to the server* @param response the response send by the server to the client* @throws ServletException if an error occurred* @throws IOException if an error occurred*/public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String filename = request.getParameter("file_name"); if (filename == null) filename = ""; filename = filename.trim();
InputStream inStream = null; String attchname = "";
byte[] b = new byte[100]; int len = 0; try { attchname = getAttachName(filename); //取得附件的名称 filename = getRealName(request, filename); //取得附件的全路径 if (filename == null) { response.setContentType("text/html; charset=GBK"); response.getWriter().print("<span style='color:red'>文件不存在,或者禁止下载!</span>"); return; } attchname = toUtf8String(attchname); //将文件转码 UTF-8 inStream = new FileInputStream(filename); response.reset(); //必须reset，否则会出现文件不完整 SmartUpload su = new SmartUpload(); // 新建一个SmartUpload对象 su.initialize(this.getServletConfig(), request, response); // 初始化 // 设定contentDisposition为null以禁止浏览器自动打开文件， //保证点击链接后是下载文件。若不设定，则下载的文件扩展名为 //doc时，浏览器将自动用word打开它。扩展名为pdf时， //浏览器将用acrobat打开。 su.setContentDisposition(null); su.downloadFile(filename); // 下载文件 //循环取出流中的数据 while ((len = inStream.read(b)) > 0) { response.getOutputStream().write(b, 0, len); } inStream.close(); } catch (Exception e) { e.printStackTrace(); }
}
/*** Initialization of the servlet. <br>** @throws ServletException if an error occurs*/public void init() throws ServletException { // Put your code here}//取得附件的名称 public static String getAttachName(String filename) { if (filename == null) return ""; filename = filename.trim(); int pos = 0; pos = filename.lastIndexOf("\\"); if (pos > -1) { filename = filename.substring(pos + 1); } pos = filename.lastIndexOf("/"); if (pos > -1) { filename = filename.substring(pos + 1); } pos = filename.lastIndexOf(File.separator); if (pos > -1) { filename = filename.substring(pos + 1); } return filename; }
//UTF8转码 public static String toUtf8String(String string) { StringBuffer sb = new StringBuffer(); for (int i = 0; i < string.length(); i++) { char c = string.charAt(i); if (c >= 0 && c <= 255) { sb.append(c); } else { byte[] b; try { b = Character.toString(c).getBytes("utf-8"); } catch (Exception ex) { System.out.println(ex); b = new byte[0]; } for (int j = 0; j < b.length; j++) { int k = b[j]; if (k < 0) k += 256; sb.append("%" + Integer.toHexString(k).toUpperCase()); } } } String s_utf8 = sb.toString(); sb.delete(0, sb.length()); sb.setLength(0); sb = null; return s_utf8; }
//取得下载文件的真实全路径名称 private String getRealName(HttpServletRequest request, String filename) { if (request == null || filename == null) return null; filename = filename.trim(); if (filename.equals("")) return null;
String filepath = request.getRealPath(filename); if (filepath == null) return null; File file = new File(filepath); if (!file.exists()) return null; return filepath; }
}