文件 - 文件下载 - 《Java笔记》

<servlet>
        <servlet-name>downLoad</servlet-name>
        <servlet-class>controller.DownLoadController</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>downLoad</servlet-name>
        <url-pattern>/downLoad</url-pattern>
    </servlet-mapping>

download.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
    <head>

    </head>
    <body>
        <a href="downLoad?fileName=美甲.txt">下载</a>
    </body>
</html>

package controller;

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

public class DownLoadController extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.获取请求传递的文件名（需要下载的文件）
        String fileName=req.getParameter("fileName");
        //2.通过fileName找到服务器中真实的文件，找到文件需要一个输入流来读取文件内容
        InputStream is=new FileInputStream("D://Test//"+fileName);
        //3.如果文件名含有中文，可能出现乱码问题，可以通过以下方式解决
        fileName= URLEncoder.encode(fileName,"UTF-8");
        //4.设置响应的contentType
        resp.setContentType("application/x-msdownload");
        resp.setHeader("Content-disposition","attachment;filename="+fileName);
        //5.将内容响应回浏览器
        OutputStream os= resp.getOutputStream();
        byte[] b=new byte[1024];
        int length=is.read(b);
        while (length!=-1){
            os.write(b,0,length);
            os.flush();
            length=is.read(b);
        }
    }
}