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servlet实现文件下载的实用类分享

程序员文章站 2024-02-08 21:02:16
复制代码 代码如下:package com; import java.io.ioexception;import java.io.printwriter;import j...

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;
 }
}