下载文件

package com.zy.down;

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;

/**
 * Servlet implementation class FileDown
 */
@WebServlet("/FileDown")
public class FileDown extends HttpServlet {
    
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        
        String file = request.getParameter("file"); //客户端传递的需要下载的文件名
        String path = request.getServletContext().getRealPath("/img")+"/"+file; //默认认为文件在当前项目的根目录
        FileInputStream fis = new FileInputStream(path);
        response.setCharacterEncoding("utf-8");
        //attachment 附件--有附件为下载，无附件为预览
        response.setHeader("Content-Disposition", "attachment; filename="+file);
        ServletOutputStream out = response.getOutputStream();
        byte[] bt = new byte[1024];
        int length = 0;
        //边读边写
        while((length=fis.read(bt))!=-1){
            out.write(bt,0,length);
        }
        out.close();

    }

    
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

jsp页面

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<a href="FileDown?file=110.jpg">下载图片</a>
</body>
</html>