Java代码实现文件下载

昨天晚上写了一篇文件上传的，今天上午把文件下载弄了一下，还是commons中的包

commons-fileupload.jar、commons-io.jar,下载位置就不说了,apache网站上找

这是一个web工程,下面有个截图

仅供参考,下面是index.jsp代码

View Code

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
    response.sendRedirect("showfile.jspx");
%>

showfile.jsp

View Code

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>文件下载</title>
  </head>
  <body>
    请选择您要下载的文件：<br/>
   <c:forEach items="${fileList}" var="fileName"> 
     <a href="download.jspx?filename=${fileName }">${fileName }</a><br/> 
    </c:forEach> 
  </body>
</html>

web.xml,这个没什么好看的,大家新建servlet时会自动完成web.xml中内容,其实就是请求servlet路径

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<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 
    xmlns="http://java.sun.com/xml/ns/javaee" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
    http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
  <display-name></display-name>
  <servlet>
    <servlet-name>ShowFileServlet</servlet-name>
    <servlet-class>ShowFileServlet</servlet-class>
  </servlet>
  <servlet>
      <servlet-name>DownLoadServlet</servlet-name>
      <servlet-class>DownLoadServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>ShowFileServlet</servlet-name>
    <url-pattern>/showfile.jspx</url-pattern>
  </servlet-mapping>
  <servlet-mapping>
      <servlet-name>DownLoadServlet</servlet-name>
      <url-pattern>/download.jspx</url-pattern>
  </servlet-mapping>    
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>

好了,下面是servlet了

ShowFileServlet.java

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import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

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


public class ShowFileServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String path="D:/file";//下载资源位置
        List<String> fileList = new ArrayList<String>();//声明集合存放目录下所有文件的文件名
        File folder = new File(path);
        //判断文件夹是否存在并且是否是一个目录
        if(folder.exists()&&folder.isDirectory()){
            //获得目录中所有文件及目录
            File[] files = folder.listFiles();
            for(File file:files){
                //如果是文件
                if(file.isFile()){
                    //将文件名放入集合
                    fileList.add(file.getName());
                }
            }
        }
        request.setAttribute("fileList", fileList);
        request.getRequestDispatcher("showfile.jsp").forward(request, response);
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        this.doGet(request, response);
    }

}

DownLoadServlet.java

View Code

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.URLEncoder;

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

public class DownLoadServlet extends HttpServlet {

    private static final long serialVersionUID = 1L;

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String path="D:/file";//资源位置
        String fileName1 = request.getParameter("filename");
        String fileName = new String(fileName1.getBytes("ISO-8859-1"),"utf-8");
        File file = new File(path+"/"+fileName);//下载资源文件
        //文件存在
        if(file.exists()){
            //设置响应类型及响应头
            System.out.println(fileName);
            response.setContentType("application/x-msdownload");
            //防止输出文件名乱码以下两种均可
            //response.setHeader( "Content-Disposition", "attachment;filename=\"" + new String( fileName.getBytes("gb2312"), "ISO8859-1" )+"\"");
            response.addHeader("Content-Disposition", "attachment;filename=\""+URLEncoder.encode(fileName,"UTF-8")+"\"");
            //读取文件
            InputStream inputStream = new FileInputStream(file);
            BufferedInputStream bis = new BufferedInputStream(inputStream);
            byte[] bytes = new byte[1024];
            ServletOutputStream outputStream = response.getOutputStream();//该对象可以在响应中写入二进制数据
            BufferedOutputStream bos = new BufferedOutputStream(outputStream);
            int readLength = 0;
            while((readLength = bis.read(bytes))!=-1){
                bos.write(bytes,0,readLength);
            }
            //释放资源
            inputStream.close();
            bis.close();
            bos.flush();
            outputStream.close();
            bos.flush();
        }
    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        this.doGet(request, response);
    }

}