http下载文件（通用格式） .jsp j ava

package com.yqcf.util;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class DownFile {
 /**
  *
  * 在jsp页面调用fileDown(request,response) url传参：dirPath(文件的全路径),fileName(文件名)
  *
  * @return boolean
  */
 public boolean fileDown(HttpServletRequest request,
   HttpServletResponse response) {
  // ************取得文件的路径和文件名***************//
  String dirPath = request.getParameter("dirPath");
  String fileName = request.getParameter("fileName");
  // ************判断文件是否存在********************//
  File file = new File(dirPath, fileName);
  if (!file.exists()) {
   System.out.println("文件下载失败：文件或路径错误");
   return false;
  }
  long fileLength = file.length();
  String length = String.valueOf(fileLength);
  // 设置返回文件的类型和头信息，application/octet-stream:文件类型的通用格式//
  response.setContentType("application/octet-stream");
  response.setHeader("Content-disposition", "attachment;filename="
    + fileName);
  response.setHeader("Content_Length", length);
  FileInputStream input = null;
  ServletOutputStream output = null;
  try {
   // **************产生输入流和输出流*************//
   input = new FileInputStream(file);
   output = response.getOutputStream();
   byte[] block = new byte[1024];
   int len = 0;
   // **************开始下载文件*****************//
   while ((len = input.read(block)) != -1) {
    output.write(block, 0, len);
   }
   output.flush();
   return true;
  } catch (IOException e) {
   System.out.println("文件下载失败：" + e.getMessage());
   return false;
  } finally {
   // *************关闭文件流****************//
   try {
    if (input != null) {
     input.close();
    }
    if (output != null) {
     output.close();
    }
   } catch (IOException ex) {
    System.out.println(ex.getMessage());
   }
  }
 }

}