Response下载文件

package com.wyl.servlet;


import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileInputStream;
import java.io.IOException;

public class FileServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //1.获取文件下载路径
        //String realPath = this.getServletContext().getRealPath("/桌面图片.png");
        String realPath = "D:\idea项目\javaweb-servlet\response\target\classes\1.png";
        System.out.println("文件路径"+realPath);
        //2.下载的文件名是什么
            //substring传递一个参数代表从索引1的字符串开始,到结束
            //路径realpath.lastIndexOf  ABCDABCD".lastIndexOf("BC") ;返回5
        String filename = realPath.substring(realPath.lastIndexOf("\") + 1);
        System.out.println("下载的文件名"+filename);
        //3让浏览器支持（Content-disposition）我们下载所需要的东西
        resp.setHeader("Content-disposition","attachment;filename="+filename);
        //4.获取要下载文件的输入流
        FileInputStream  in = new FileInputStream(realPath);
        //5.创建缓冲区
        int len=0;
        byte [] buffer=new byte[1024];
        //6.获取outputStream对象
        ServletOutputStream outputStream = resp.getOutputStream();
        //7.将FileInputStream写道buff缓冲区
        while ((len=(in.read(buffer)))>0){
            //8.相应到客户端
            outputStream.write(buffer,0,len);
        }
        //关闭流
        in.close();
        outputStream.close();
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doGet(req, resp);
    }
}