服务器通过IO流响应图片数据

在上一篇文章里，介绍了Android客户端如何通过IO流（http://blog.csdn.net/ceovip/article/details/79100368），从服务器获取图片数据。这里的服务器端测试代码比较简单，示例如下：

package com.li.downloadtest;

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

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


public class DownloadServlet extends HttpServlet {

    /**
     * The doGet method of the servlet. <br>
     *
     * This method is called when a form has its tag value method equals to get.
     * 
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        doPost(request, response);
    }

    /**
     * The doPost method of the servlet. <br>
     *
     * This method is called when a form has its tag value method equals to post.
     * 
     * @param request the request send by the client to the server
     * @param response the response send by the server to the client
     * @throws ServletException if an error occurred
     * @throws IOException if an error occurred
     */
    @SuppressWarnings("static-access")
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        //读取输入流数据
        ServletInputStream is = request.getInputStream();
        BufferedReader bufRd = new BufferedReader(new InputStreamReader(is, "UTF-8"));

        StringBuffer strBuf = new StringBuffer();
        String strContent = new String("");
        while((strContent = bufRd.readLine()) != null){
            strBuf.append(strContent);
        }
        //获取请求参数
        String jsStr = strBuf.toString();
        System.out.println("param--->" + jsStr);

        //输出图片数据
        try {
            response.setContentType("image/jpeg;charset=UTF-8");
            OutputStream out = response.getOutputStream();

            String imgUrl = "C:\\Users\\lish\\Desktop\\test.jpg";
            FileInputStream fis = new FileInputStream(imgUrl);

            int len = -1;
            byte[] data = new byte[1024];  

            while((len = fis.read(data)) != -1){
                out.write(data, 0 , len);
            }

            fis.close();
            out.close();

        } catch (Exception e) {

            PrintWriter writer = response.getWriter(); 
            response.setContentType("text/html;charset=UTF-8"); 
            writer.write("无法打开图片!"); 
            writer.close(); 
        }
    }
}