从服务器下载文件 DownloadServlet()

.html代码

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>

    <h1>
        使用<a>标签的方式实现文件下载
    </h1>
    <a href="/WEB14/download/a.txt">a.txt</a>
    <br>
    <a href="/WEB14/download/a.jpg">a.jpg</a>

    <h1>使用服务器端编码的方式实现文件下载</h1>
    <a href="/WEB14/downloadServlet?filename=a.txt">a.txt</a>
    <br>
    <a href="/WEB14/downloadServlet?filename=a.jpg">a.jpg</a>
    <br>
    <a href="/WEB14/downloadServlet2?filename=你的名字.txt">你的名字</a>

</body>
</html>

1.DownloadServlet()代码

package com.hdh.content;

import java.io.FileInputStream;
import java.io.IOException;

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 {
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        //1.获取下载文件的名称
        String filename=request.getParameter("filename");
        //*告诉客户端这个文件不是解析 而是以附件的形式下载
        response.setHeader("Content-Disposition", "attachment;filename="+filename);
        //2.获取文件的绝对路径
        String path=this.getServletContext().getRealPath("download/"+filename);
        //3.获得该文件的输入流
        FileInputStream in=new FileInputStream(path);
        //获得输出流---通过response获得的输出流  用于向客户端写内容
        ServletOutputStream out=response.getOutputStream();
        //拷贝文件
        int len=0;
        byte [] buffer=new byte[1024];

        while((len=in.read(buffer))>0) {
            out.write(buffer, 0, len);
        }
        in.close();
        out.close();
    }
    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        doGet(request, response);
    }

}

2.在服务器上运行后出现图片无法下载而是直接解析：

需要不进行解析而是以附件的形式下载：告诉客户端这个文件不是解析 而是以附件的形式下载

加上：response.setHeader("Content-Disposition", "attachment;filename="+filename);

package com.hdh.content;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

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 DownloadServlet2 extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        /*
         * 解决下载 你的名字.txt时乱码的问题
         */
        //1.获取下载文件的名称
        String filename=request.getParameter("filename");

        filename=new String(filename.getBytes("ISO8859-1"),"UTF-8");
        //*告诉客户端这个文件不是解析 而是以附件的形式下载
        response.setHeader("Content-Disposition", "attachment;filename="+filename);
        //2.获取文件的绝对路径
        String path=this.getServletContext().getRealPath("download/"+filename);
        //3.获得该文件的输入流
        InputStream in=new FileInputStream(path);
        //获得输出流---通过response获得的输出流  用于向客户端写内容
        ServletOutputStream out=response.getOutputStream();
        //拷贝文件
        int len=0;
        byte [] buffer=new byte[1024];

        while((len=in.read(buffer))>0) {
            out.write(buffer, 0, len);
        }
        in.close();
        out.close();
    }

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

}

3.如果在获取中文文件名时,文件名时乱码问题

filename=new String(filename.getBytes("ISO8859-1"),"UTF-8");