下载乱码问题

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);
}

}