文件下载

一、后台程序

package com.gjxx.gps.common;

import com.gjxx.util.PropertiesUtil;

import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.util.Properties;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * 文件下载既可以是get请求也可以是post
 * @author Administrator
 *
 */
public class DownLoadServlet extends HttpServlet{

   @Override
   protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
      doPost(req, resp);
   }

   @Override
   protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
      req.setCharacterEncoding("UTF-8");
      String name = req.getParameter("name");
      String[] buffer = name.split("/");
      String fileName = buffer[buffer.length-1];//获取要下载的文件名

      // 读取相关的配置
      Properties ossProp = PropertiesUtil.Oss();
      String ossUrl = "";
      if(ossProp.get("oss.url") != null){
         ossUrl = ossProp.get("oss.url").toString();
      }
      URL url = new URL(ossUrl+name);
      HttpURLConnection conn = (HttpURLConnection)url.openConnection();
      //设置超时间为3秒
      conn.setConnectTimeout(3*1000);
      //防止屏蔽程序抓取而返回403错误
      conn.setRequestProperty("User-Agent", "Mozilla/4.0 (compatible; MSIE 5.0; Windows NT; DigExt)");

      //设置响应头，对文件进行url编码
      fileName = URLEncoder.encode(fileName, "UTF-8");
      resp.setHeader("Content-Disposition", "attachment;filename="+fileName);
      resp.setContentType("application/force-download");//应用程序强制下载

      //得到输入流
      InputStream inputStream = conn.getInputStream();
      //获取自己数组
      byte[] getData = readInputStream(inputStream);

      OutputStream out = resp.getOutputStream();
      out.write(getData);
      if(out!=null){
         out.close();
      }
      if(inputStream!=null){
         inputStream.close();
      }
   }
   /**
    * 从输入流中获取字节数组
    * @param inputStream
    * @return
    * @throws IOException
    */
   public static  byte[] readInputStream(InputStream inputStream) throws IOException {
      byte[] buffer = new byte[1024];
      int len = 0;
      ByteArrayOutputStream bos = new ByteArrayOutputStream();
      while((len = inputStream.read(buffer)) != -1) {
         bos.write(buffer, 0, len);
      }
      bos.close();
      return bos.toByteArray();
   }

}

二、web.xml配置文件

<servlet>
   <servlet-name>DownLoadServlet</servlet-name>
   <servlet-class>com.gjxx.gps.common.DownLoadServlet</servlet-class>
</servlet>

<servlet-mapping>
   <servlet-name>DownLoadServlet</servlet-name>
   <url-pattern>/servlet/DownLoadServlet</url-pattern>
</servlet-mapping>

三、jsp和js文件

<a href='#' onclick=Down('"+d.filePath+"')><img src='"+path+"/static/img/sortdown23_21.png' alt='下载文件' title='下载文件'/></a>

function Down(filePath) {
    window.open(path+"/servlet/DownLoadServlet?name="+filePath);
}