jsp实现Servlet文件下载的方法

 package com; import java.io.IOException; import java.io.PrintWriter; import java.net.URLEncoder; import java.util.Date; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import com.sun.xml.internal.messaging.saaj.packaging.mime.internet.MimeUtility; /** * 文件下载类。为了防止客户端浏览器直接打开目标文件（例如在装了MS Office套件的Windows中的IE浏览器可能就会直接在IE浏览器中打开你想下载的doc或者xls文件），在响应头里加入强制下载的MIME类型。 */ public class DownloadFile extends HttpServlet { private static final Log log = LogFactory.getLog(DownloadFile.class); public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException { long timeStart = 0; if(log.isDebugEnabled()){ timeStart=System.currentTimeMillis(); } response.setContentType("application/x-download charset=UTF-8"); java.io.FileInputStream fis = null; String filepath = request.getRealPath(""); javax.servlet.ServletOutputStream sos = null; // System.out.println("DownloadFile filename:" + filename); try { if(request.getParameter("filename")==null ||request.getParameter("showName")==null){ return; } String filename = request.getParameter("filename"); String showName = request.getParameter("showName"); request.setCharacterEncoding("UTF-8"); response.setCharacterEncoding("UTF-8"); java.io.File file = new java.io.File(filepath + filename); if (!file.exists()) { log.error(file.getAbsolutePath() + " 文件不存在!"); return; } // 读取文件流 fis = new java.io.FileInputStream(file); // 设置下载保存的文件名 sos = response.getOutputStream(); showName += filename.substring(filename.lastIndexOf(".")); String contentDisposition = "", browser = getBrowser(request); if ("IE".equals(browser)) { contentDisposition = "attachment; filename=" + URLEncoder.encode(showName, "UTF-8").replace("+", "%20"); } else if ("CH".equals(browser)) { contentDisposition = "attachment; filename=" + MimeUtility.encodeText(showName, "UTF8", "B"); } else if ("SF".equals(browser)) { contentDisposition = "attachment; filename=" + new String(showName.getBytes("UTF-8"), "ISO8859-1"); } else { contentDisposition = "attachment; filename*=UTF-8''" + URLEncoder.encode(showName, "UTF-8").replace("+", "%20"); } response.setHeader("Content-Disposition", contentDisposition); int byteCount = 0; if (fis != null) { byte[] buff = new byte[1024]; int bytesRead; while(-1 != (bytesRead = fis.read(buff, 0, buff.length))) { sos.write(buff, 0, bytesRead); sos.flush(); byteCount += bytesRead; } } sos.flush(); if(log.isDebugEnabled()){ log.debug("文件下载完成，文件大小："+ byteCount +"，总共用时:"+ (new Date().getTime() - timeStart) +"毫秒。"); } } catch(IOException ioe) { ioe.printStackTrace(); } finally { try { if(fis!=null){ fis.close(); } } catch (IOException e) { } finally { try { if(sos!=null){ sos.close(); } } catch (IOException e) { } } } } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html"); PrintWriter out = response.getWriter(); out.println(""); out.println(""); out.println(" "); out.println("  "); out.println("  "); out.println(" "); out.println(" "); out.print(" This is "); out.print(this.getClass().getName()); out.println(", using the POST method"); out.println(" "); out.println(""); out.flush(); out.close(); } private String getBrowser(HttpServletRequest request) { String userAgent = request.getHeader("USER-AGENT").toLowerCase(); if (userAgent != null) { if (userAgent.indexOf("msie") >= 0) { return "IE"; } else if (userAgent.indexOf("mozilla") >= 0) { return "FF"; } else if (userAgent.indexOf("applewebkit") >= 0) { return "CH"; } else if (userAgent.indexOf("safari") >= 0) { return "SF"; } else if (userAgent.indexOf("opera") >= 0) { return "OP"; } } return null; } }