一、放置一张图片

 二、创建servlet读取图片

 public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
		ServletOutputStream out = response.getOutputStream();                                                                       
		ServletContext context = this.getServletContext();                                                            
		// 获取文件绝对路径                                                                                                   
		String path = context.getRealPath("/WEB-INF/classes/cn/itcast/servlet/1.png");                                      
		FileInputStream in = new FileInputStream(path);                                                               
		response.setContentType("image/png");//告诉浏览器显示图片
        //response.setContentType("multipart/form-data");//告诉浏览器下载图片
        out = response.getOutputStream();
        //读取文件流
        int len = 0;
        byte[] buffer = new byte[1024 * 10];
        while ((len = in.read(buffer)) != -1){
            out.write(buffer,0,len);
        }
        out.flush();                                             
    }