文件的下载

来源：互联网发布：大学生如何找兼职知乎编辑：程序博客网时间：2024/05/19 04:04

package com.jsun.servlet;

import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.jsun.entity.FileMes;
import com.jsun.service.FileMesService;
import com.jsun.util.MyBeanFactory;

/**
* Servlet implementation class DownloadServlet
*/
@WebServlet(urlPatterns={"/DownloadServlet.jsp"})
public class DownloadFileServlet extends HttpServlet {

     public static final String FILE_DIR="d:/assets/files/";
private static final long serialVersionUID = 1L;

    /**
     * @see HttpServlet#HttpServlet()
     */
    public DownloadFileServlet() {
        super();
    }

/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}

/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   long id=Long.parseLong(request.getParameter("id"));
   String MIME="application/msword";   //文件MIME类型
   String fileName=MyBeanFactory.beanFactory.getBean("fileMesServiceImpl", FileMesService.class).getFileMes(new FileMes(id)).getName();

   downLoad(FILE_DIR+fileName, MIME, request, response);
}
/**
* 执行下载
* @param filePath
* @param MIME
* @param request
* @param response
* @throws IOException
*/
private void downLoad(String filePath,String MIME,HttpServletRequest request, HttpServletResponse response) throws IOException{
  File file = new File(filePath); //取得要传送的文件，实际应用时可以将文件路径以参数的形式传入
        long fileSize = file.length(); //文件长度
        byte[] b=new byte[1024];
        FileInputStream fin = new FileInputStream(file);
        DataInputStream in = new DataInputStream(fin);

//      设置响应头信息，让下载的文件显示保存信息
        response.setContentType("application/x-msdownload; charset=gbk");
        response.setHeader("Content-disposition", "attachment;filename="+new String(file.getName().getBytes("gbk"),"ISO8859_1"));
        response.setContentType(MIME); //设置输出流的MIME类型
        response.setContentLength((int) fileSize); //有什么区别
//      response.setHeader("Content-length", filesize);

        ServletOutputStream servletOut = response.getOutputStream();
//      发送文件数据，每次1024字节，最后一次单独计算
        long totalsize = 0;
        while(totalsize<fileSize){
            totalsize+=1024;
            if(totalsize>fileSize){ //最后一次传送的字节数
                byte[] leftpart = new byte[1024-(int)(totalsize-fileSize)];
                in.readFully(leftpart);
                servletOut.write(leftpart);
            }
            else{
                in.readFully(b); //读1024个字节至字节数组b
                servletOut.write(b);
            }
        }
        servletOut.close();
}

}