下载

下载的要求
  * 两个头一个流！
    > Content-Type：传递给客户端的文件是什么MIME类型，例如：image/pjpeg
      * 通过文件名称调用ServletContext的getMimeType()方法，得到MIME类型！
    > Content-Disposition：它的默认值为inline，表示在浏览器窗口中打开！attachment;filename=xxx
      * 在filename=后面跟随的是显示在下载框中的文件名称！
    > 流：要下载的文件数据！

<pre name="code" class="java">package servlet;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintWriter;

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

import org.apache.commons.io.IOUtils;

public class DownloadServlet1 extends HttpServlet {


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

		String filename="E:/吻别.mp3";
		//为了使下载框中的中文不出现乱码
	//	String framename=new String ("吻别.mp3".getBytes("GBK"),"ISO-8859-1");
		String framename=filenameEncoding("吻别.mp3",request);
		//获取流
		FileInputStream fis=new FileInputStream(filename);
		//获取头
		String contentType=this.getServletContext().getMimeType(filename);
		String contentDisposition ="attachment;filename="+framename;
		//设置头
		response.setHeader("Content-Type", contentType);
		response.setHeader("Content-Disposition",contentDisposition);
		
		//获取绑定了响应端的流
		ServletOutputStream sos=response.getOutputStream();
		//把输入流中的数据写入到输出流
		IOUtils.copy(fis, sos); 
		fis.close();
		
	}
	public static String filenameEncoding(String filename, HttpServletRequest request) throws IOException {
		String agent = request.getHeader("User-Agent"); //获取浏览器
		if (agent.contains("Firefox")) {
			BASE64Encoder base64Encoder = new BASE64Encoder();
			filename = "=?utf-8?B?"
					+ base64Encoder.encode(filename.getBytes("utf-8"))
					+ "?=";
		} else if(agent.contains("MSIE")) {
			filename = URLEncoder.encode(filename, "utf-8");
		} else {
			filename = URLEncoder.encode(filename, "utf-8");
		}
		return filename;
	}

	

}