java编写的下载程序无法显示图片 求大神指点 （详解）

代码如下：
package com.servelttest;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
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 FileDownLoad extends HttpServlet {

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

response.setContentType("text/html;charset=utf-8");
response.setCharacterEncoding("utf-8");
//System.out.println("<h1>fveveve！</h1>");
//System.out.println("<br/>");
try {
PrintWriter out = response.getWriter();

//演示下载文件
//告诉浏览器有东西要下载
response.setHeader("Content-Disposition","attachment;filename=1.jpg");
//获取要下载的文件的全路径
//String path=this.getServletContext().getRealPath("/images/5.png");
//String path=this.getServletContext().getResourcePaths("/images/5.png");
InputStream in = this.getServletContext().getResourceAsStream("/images/1.jpg");
//创建文件输入流
//FileInputStream fis=new FileInputStream(path);
//做一个缓冲字节数组
byte buff[]=new byte[1024];
int len=0;
OutputStream os=response.getOutputStream();
while((len=in.read(buff))>0){
os.write(buff, 0, len);
}
os.close();
in.close();

} catch (Exception e) {

}

}

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

this.doGet(request, response);
}

}