java 下载文件 && 下载文件名中文乱码问题

package com.itheima.login;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.URLEncoder;

import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import sun.misc.BASE64Encoder;


public class ServletDownload extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //response.getWriter().append("Served at: ").append(request.getContextPath());

        String filename = request.getParameter("filename");

        //解决获得中文参数的乱码问题----
        filename = new String(filename.getBytes("ISO8859-1"),"UTF-8");//美女.jpg


        //获得请求头中的User-Agent
        String agent = request.getHeader("User-Agent");
        //根据不同浏览器进行不同的编码
        String filenameEncoder = "";
        if (agent.contains("MSIE")) {
            // IE浏览器
            filenameEncoder = URLEncoder.encode(filename, "utf-8");
            filenameEncoder = filenameEncoder.replace("+", " ");
        } else if (agent.contains("Firefox")) {
            // 火狐浏览器
            BASE64Encoder base64Encoder = new BASE64Encoder();
            filenameEncoder = "=?utf-8?B?"
                    + base64Encoder.encode(filename.getBytes("utf-8")) + "?=";
        } else {
            // 其它浏览器
            filenameEncoder = URLEncoder.encode(filename, "utf-8");             
        }



        //System.out.println(filename);
        //要下载的文件类型----客户端通过文件的MINE类型区分类型
        String mimeType = this.getServletContext().getMimeType(filename);

        response.setContentType(mimeType);
        //告诉客户端该文件不是直接解析而是以附件形式打开(下载)
        response.setHeader("Content-Disposition", "attachment;filename="+filenameEncoder);

        //获取文件的绝对路径
        String filePath = this.getServletContext().getRealPath(filename);

        ServletOutputStream outputStream = response.getOutputStream();

        FileInputStream in = new FileInputStream(filePath);

        byte[] buffer = new byte[1024];
        int len = 0;
        while ((len = in.read(buffer)) > 0) {
            outputStream.write(buffer);
        }

        in.close();

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //doGet(request, response);
    }

}