文件的处理操作

不得不说，在一次次的学习过程中，我慢慢的明白了web操作的一些常见的问题关于路径的问题也渐渐明白了

<%--
  Created by IntelliJ IDEA.
  User: mr.wang
  Date: 2021/10/31
  Time: 22:35
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>$Title$</title>
  </head>
  <body>
<%--创建不同的接收方式--%>
<%--将数据传到servlet里面--%>
  <a href="/_war_exploded/download?type=png">猫粮</a>
<hr/>
  <a href="/_war_exploded/download?type=txt">java学习资源包</a>
  </body>
</html>

上面为最基本的前端的跳转界面

将数据跳转到指定的servlet里面

package com.wx.servlet;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
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;

@WebServlet("/download")
public class DownloadServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//      获取要下载的文件的类型
        String type = req.getParameter("type");
//      先设置文件名为空
        String fileName="";
//        判断文件的格式类型
        switch (type) {
            case"png":{
                fileName = "1.png";
                        break;
            }
            case "txt":{
                fileName = "javadata.txt";
                break;
            }
        }
        //设置响应的方式,下面是下载之后的文件名
        resp.setContentType("application/x-msdownload");
//        String fileName = "1.png";
        //设置下载后的文件名,其他地方都是写死的
        resp.setHeader("Content-Disposition","attachment;filename="+fileName);
        //获取输出流
        OutputStream outputStream =resp.getOutputStream();
        String path = req.getServletContext().getRealPath("file/"+fileName);
        InputStream inputStream = new FileInputStream(path);
        int temp = 0;
//      循环操作
        while ((temp = inputStream.read())!=-1) {
            outputStream.write(temp);
        }

        //关闭输入与输出流
        inputStream.close();
        outputStream.close();
    }

}