Servlet实现文件的下载

（1）项目的主文件夹例如以下：（演示出image和servlet的位置所在）

（2）详细实现的代码例如以下：

package com.lc.HttpTest;

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

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

public class xiazaiwenjian extends HttpServlet {

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

		response.setContentType("text/html");
		
		//演示下载文件
		response.setHeader("Content-Disposition","attachment;filename=1.jpg");
		
		//打开文件     web网站下载文件的原理  先把文件读进servlet的内存  把文件发送给浏览器段
		//字符流仅仅能发文本     字节流发文件
		
		//1获取要下载文件的全路径
		String path = this.getServletContext().getRealPath("/images/1.jpg");
		//2创建文件传输流
		FileInputStream fis = new FileInputStream(path);
		//做一个缓冲字节数组
		byte buff[] = new byte[1024];
		int len = 0; //实际每次读取的字节数
		OutputStream os = response.getOutputStream();
		while((len=fis.read(buff)) > 0){
			os.write(buff,0,len);
		}
		
		//关闭
		os.close();
		fis.close();	

	}

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

		this.doGet(request, response);
	}

}