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;

/**
 * 中文文件名问题
 */
@WebServlet("/Servlet_demo2")
public class Servlet_demo2 extends HttpServlet {
    /*
	    * 解决思路：
	    	1. 获取客户端使用的浏览器版本信息
	    	2. 根据不同的版本信息，设置filename的编码方式不同
     */
    @Override
    public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1. 定义页面，编辑超链接href属性，指向Servlet_demo1，传递资源名称filename
        //2、获取请求参数，文件名称
        String filename = request.getParameter("filename");

        //3、读取文件 -- 找到文件真实路径，读入内存，输出文件流
        ServletContext servletContext = this.getServletContext();
        String realPath = servletContext.getRealPath("/img/" + filename);

        FileInputStream fileInputStream = new FileInputStream(realPath);//加载文件，进入内存

        //4、设置response的响应头
        String mimeType = servletContext.getMimeType(filename);//获取文件类型
        response.setContentType(mimeType);//告诉浏览器如何解析

        //解决中文文件名乱码问题
        //获取user-agent请求头
        String agent = request.getHeader("user-agent");
        filename = DownLoadUtils.getFileName(agent, filename);

        //设置文件的展示方式 -- 下载下来
        response.setHeader("content-disposition", "attachment;filename=" + filename);

        //输出
        ServletOutputStream outputStream = response.getOutputStream();
        byte[] bytes = new byte[1024 * 8];
        int len = 0;
        while ((len = fileInputStream.read(bytes)) != -1) {
            outputStream.write(bytes, 0, len);
        }

        //关闭流
        fileInputStream.close();


    }

    @Override
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doGet(request, response);
    }

}