package com.lsm.web.servlet;

import com.lsm.utils.DownLoadUtils;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
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;

@WebServlet("/downLoadServlet")
public class DownLoadServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request,response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.获取要下载的文件名称
        String filename = request.getParameter("filename");
        //2.找到文件在服务器中的真实路径
        ServletContext servletContext = this.getServletContext();
        String realPath = servletContext.getRealPath("/image/" + filename);
        //3.关联输入流
        FileInputStream fis=new FileInputStream(realPath);
        //设置响应文件类型
        String mimeType = servletContext.getMimeType(filename);
        response.setHeader("content-type",mimeType);
        //通过user-agenet判断来源那个浏览器
        String agent = request.getHeader("user-agent");
        System.out.println(agent);
        //借助工具类解决附件弹窗的中文乱码
        filename = DownLoadUtils.getFileName(agent,filename);
        //下载时弹出附件框
        response.setHeader("content-disposition","attachment;filename="+filename);
        //通过sos交互到浏览器
        ServletOutputStream sos = response.getOutputStream();
        byte[] buff=new byte[1024*10];
        int len=0;
        while ((len=fis.read(buff))!=-1){
            sos.write(buff,0,len);
        }
        fis.close();

    }
}

package com.lsm.web.servlet;

import com.lsm.utils.DownLoadUtils;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
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;

@WebServlet("/downLoadServlet")
public class DownLoadServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request,response);
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.获取要下载的文件名称
        String filename = request.getParameter("filename");
        //2.找到文件在服务器中的真实路径
        ServletContext servletContext = this.getServletContext();
        String realPath = servletContext.getRealPath("/image/" + filename);
        //3.关联输入流
        FileInputStream fis=new FileInputStream(realPath);
        //设置响应文件类型
        String mimeType = servletContext.getMimeType(filename);
        response.setHeader("content-type",mimeType);
        //通过user-agenet判断来源那个浏览器
        String agent = request.getHeader("user-agent");
        System.out.println(agent);
        //借助工具类解决附件弹窗的中文乱码
        filename = DownLoadUtils.getFileName(agent,filename);
        //下载时弹出附件框
        response.setHeader("content-disposition","attachment;filename="+filename);
        //通过sos交互到浏览器
        ServletOutputStream sos = response.getOutputStream();
        byte[] buff=new byte[1024*10];
        int len=0;
        while ((len=fis.read(buff))!=-1){
            sos.write(buff,0,len);
        }
        fis.close();

    }
}