servlet文件下载类的详细介绍

来源:爱站网时间:2022-09-30编辑:网友分享
小编来给大家分享下servlet文件下载类的详细内容,servlet文件下载类为了防止客户端浏览器直接打开目标文件在响应头里加入强制下载的MIME类型,想要了解详情,看看爱站技术频道小编整理的资料吧!

 

复制代码 代码如下:
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("<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Transitional//EN\" \"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd\">");
  out.println("<html>");
  out.println(" <head>");
  out.println("   <title>文件下载</title>");
  out.println("   <meta http-equiv=\"Content-Type\" content=\"text/html; charset=UTF-8\" />");
  out.println(" </head>");
  out.println(" <body>");
  out.print(" This is ");
  out.print(this.getClass().getName());
  out.println(", using the POST method");
  out.println(" </body>");
  out.println("</html>");
  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;
 }
}

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