package chensi.com;

import java.io.FileInputStream;

import java.io.IOException;

import java.net.URLEncoder;

import java.nio.file.FileAlreadyExistsException;

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;

/**

 * Servlet HttpServletResponse 下载文件  ,浏览器提示我们将图片下载下来。

 */

@WebServlet("/ResponseDemo7")

public class ResponseDemo7 extends HttpServlet {

    private static final long serialVersionUID = 1L;

    /**

     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)

     */

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

        //通过路径将图片以流的形式得到

        //通过相对路径得到绝对路径

        String path = this.getServletContext().getRealPath("/WEB-INF/classes/爪哇.jpg");

        //有了路径可以得到输入流（图片，要用字节输出流）

        FileInputStream fis = new FileInputStream(path); //使用绝对路径将图片用输入流变成一个流  fis（图片）

        //用response创建一个输出流

        ServletOutputStream outputStream = response.getOutputStream();    

        /*我们要将图片下载下来 */

        //得到要下载的文件名

        String fileName = path.substring(path.lastIndexOf("\\")+1);

        System.out.println(fileName);

        //设置文件的编码

        fileName = URLEncoder.encode(fileName,"UTF-8");

        //告知客户端要下载文件

        response.setHeader("content-disposition", "attachment;filename="+fileName);

        response.setHeader("content-type", "image/jpeg");

        //执行fileOutputStream的输出操作

        int len = 1;

        byte[] b = new byte[1024];

        while((len=fis.read(b))!=-1){

            outputStream.write(b, 0, len);

        }

        outputStream.close();

        fis.close();

    }

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

        // TODO Auto-generated method stub

        doGet(request, response);

    }

}