图片下载，将真实的图片送到浏览器

package com.zr;

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

import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class DownPicture
 */
@WebServlet("/DownPicture")
@MultipartConfig
public class DownPicture extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public DownPicture() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		doPost(request, response);
	}

	/**
	 * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
				//处理文件下载
				//通过设置响应头
				response.setContentType("application/x-download");
				response.addHeader("Content-Dsiposition", "attachment;filename=pic.jpg");
				//将真实的图片送到浏览器
				OutputStream out = response.getOutputStream();
				//获取地址
				String downaddress = request.getParameter("downAddress");
				//3,创建文件输入流对象FileInputStream
				InputStream in = new FileInputStream(downaddress);
				//字节数组
						//4,定义字节数组
						byte[] buffer = new byte[1024];
						//len是实际的长度
						int len = in.read(buffer);
						while(len != -1){
							//5，将图片写入输出流中（相当于文件拷贝）
							out.write(buffer, 0, len);//长度为len ,从0开始
							len = in.read(buffer);
						
						}
						//6，关闭
							in.close();
							out.close();
	}

}