Servlet response下载文件

package com.wlt.response.c.body;

import java.io.IOException;
import java.io.InputStream;

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 org.apache.tomcat.util.http.fileupload.IOUtils;

/**
 * 文件下载
 */
@WebServlet("/download")
public class DownloadServlet 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 {
        // 
        String filename = request.getParameter(" ");
        ServletContext s = this.getServletContext();
        //设置mine
        String mt = s.getMimeType(filename);
        response.setContentType(mt);
        
        //设置下载头信息
        response.setHeader("content-disposition", "attchment;filename="+filename);
        //对考流
        //获取输入流
        InputStream is = s.getResourceAsStream("/download/"+filename);
        //获取输出流
        ServletOutputStream os = response.getOutputStream();
        
        /*  第一种

        int len=-1;
        byte[] b=new byte[1024];
        while ((len=is.read(b))!=-1) {
            os.write(b,0,len);
        }*/

     // 第二种：利用工具类的方法commons-io-1.4.rar
        IOUtils.copy(is, os);
        //关流
        os.close();
        is.close();
    }
        
    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}