JSP下载文件

文件上传
浏览器在上传的过程中是将文件以流的形式提交到服务器端,一般选择采用apache的开源工具common-fileupload这个文件上传组件，common-fileupload依赖于common-io包，因此开发工程中需要导入common-fileupload 和 common-io包。 


文件下载
对于网站来说，网站本身常常需要提供一些资源或者资料进行下载，说到下载莫过于最原始的方法就是在网页上提供下载的网址。 

Content-disposition 是 MIME 协议的扩展，MIME 协议指示 MIME 用户代理如何显示附加的文件。当 Internet Explorer接收到头时，它会激活文件下载对话框，它的文件名框自动填充了头中指定的文件名。（请注意，这是设计导致的；无法使用此功能将文档保存到用户的计算机上，而不向用户询问保存位置。

一.ListFile.java

1.递归遍历指定目录下的所有文件和目录,并将文件名存储到Map集合中

package com.control;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

/**
 * Created by Ray on 2018/3/16 0016.
 **/
public class ListFile extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request,response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取指定目录
        String FilePath = "f:/test";
        //存储要下载的文件名
        Map fileNameMap = new HashMap();
        //递归遍历filepath目录下的所有文件和目录,将文件名存储到map集合中
        listfile(new File(FilePath),fileNameMap);//File既可以代表一个文件也可以代表一个目录
        //将Map集合发送到listfile.jsp页面显示
        request.setAttribute("fileNameMap", fileNameMap);
        request.getRequestDispatcher("listfile.jsp").forward(request,response);
    }

    /**
    * @Author: Ray
    * @Date: 2018/3/17 0017
    * @Description: 递归遍历指定目录下的所有文件和目录,并将文件名存储到Map集合中
    * @Return: 
    */
    public void listfile(File file,Map map){
        //如果file代表的不是一个文件,而是一个目录
        if(!file.isFile()){
            //列出该目录下的所有文件和目录
            File[] files = file.listFiles();
            //遍历files[]数组
            for(File f:files){
                //递归
                listfile(f,map);
            }
        }else{
            String fileOrgName = file.getName();
            int index = fileOrgName.lastIndexOf(".");
            String fileName = fileOrgName.substring(0,index);
            System.out.println(file.getName());
            map.put(file.getName(),fileName);
        }
    }
}

二.listfile.jsp

1.遍历Map集合

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<%
    String path = request.getContextPath();
    String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + path + "/";
%>




    

    

    
    
    
    
    
    




    
    
        
            
        
        ${fileItem.value}下载
        

    

三.Download.java

1.设置响应头,控制浏览器下载该文件

2.JSP文件下载中文和空格显示Content-Disposition设置

package com.control;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.net.URLEncoder;

/**
 * Created by Ray on 2018/3/16 0016.
 **/
public class Download extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request,response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //得到要下载的文件名
        String fileName = request.getParameter("filename");
        //要下载的文件的目录
        String fileSavePath = "f:/test";
        //要下载的文件
        File file = new File(fileSavePath + File.separator + fileName);
        //如果文件不存在
        if(!file.exists()){
            request.setAttribute("info","您要下载的资源已被删除!");
            request.getRequestDispatcher("messagedownload.jsp").forward(request,response);
            return;
        }

        //设置响应头,控制浏览器下载该文件
        response.setHeader("content-disposition","attachment;filename*=UTF-8''" + URLEncoder.encode(fileName,"UTF-8").replaceAll("\\+", "%20"));
        //读取要下载的文件,保存到文件输入流
        FileInputStream in = new FileInputStream(fileSavePath + File.separator + fileName);
        //创建输出流
        OutputStream out = response.getOutputStream();
        //创建缓冲区
        byte buffer[] = new byte[1024];
        int len = 0;
        //循环将输入流中的内容读取到缓冲区当中
        while(0<=(len=in.read(buffer))){
            //输出缓冲区的内容到浏览器,实现文件下载
            out.write(buffer, 0, len);
        }
        //关闭文件输入输出流
        out.close();
        in.close();
    }
}

四.messagedownload.jsp

1.输出提示信息

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8" %>
<%
    String path = request.getContextPath();
    String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + path + "/";
%>




    

    

    
    
    
    
    
    
    




下载操作

    <%
        //获取提示信息
        String info = String.valueOf(request.getAttribute("info"));
        //如果提示信息不为空,则输出提示信息
        if (info != "null") {
            out.print(info);
        }
    %>

五.web.xml

    
        BookList
        com.control.BookList
    
    
        BookList
        /BookList
    

    
        BookAdd
        com.control.BookAdd
    
    
        BookAdd
        /BookAdd
    

    
        BookUpdate
        com.control.BookUpdate
    
    
        BookUpdate
        /BookUpdate
    

    
        BookDoUpdate
        com.control.BookDoUpdate
    
    
        BookDoUpdate
        /BookDoUpdate
    

    
        BookDelete
        com.control.BookDelete
    
    
        BookDelete
        /BookDelete
    

    
        BookDoDelete
        com.control.BookDoDelete
    
    
        BookDoDelete
        /BookDoDelete
    

    
        BookBatchAdd
        com.control.BookBatchAdd
    
    
        BookBatchAdd
        /BookBatchAdd
    

    
        BookBatchDelete
        com.control.BookBatchDelete
    
    
        BookBatchDelete
        /BookBatchDelete
    

    
        BookFind
        com.control.BookFind
    
    
        BookFind
        /BookFind
    


    
    
        Login
        com.control.Login
    

    
        Login
        /Login
    

    
        DrawImage
        com.control.DrawImage
    
    
        DrawImage
        /DrawImage
    

    
        Register
        com.control.Register
    
    
        Register
        /Register
    

    
        LoginUser
        com.control.LoginUser
    
    
        LoginUser
        /LoginUser
    

    
        ExitLogin
        com.control.ExitLogin
    
    
        ExitLogin
        /ExitLogin
    


    
        Upload
        com.control.Upload
    
    
        Upload
        /Upload
    

    
        ListFile
        com.control.ListFile
    
    
        ListFile
        /ListFile
    

    
        Download
        com.control.Download
    
    
        Download
        /Download
    

    
    
        
        
        
            
            
        
    
    
        
        
    

    
    
        CharSetFilter
        com.Filter.CharSetFilter
        
            
            charset
            UTF-8
        
    

    
    
        CharSetFilter
        
        /*
    

    
    
        404
        /error/error404.jsp
    
    
        500
        /error/error500.jsp
    
    
        ErrorFilter
        com.Filter.ErrorFilter
    
    
        ErrorFilter
        /error.jsp
        ERROR
    

六.页面效果

ok!