实现简单图片下载功能及防盗链

@Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置编码
                response.setContentType("text:html;charset=utf-8");
        
        //下载功能，并实现防盗链
        String referer = request.getHeader("Referer"); //获取Referer上的链接信息
                //判断连接是否为空或者是以自己项目名开头
        if(referer == null || !referer.startsWith("http://localhost:8080/day1111")){
            response.sendRedirect("/day1111/error.html");
            return;   //阻止代码往下运行
        }
        
        //下载功能实现
        String temp = request.getParameter("filename");
        String filename = URLEncoder.encode(temp, "utf-8");  //避免页面显示文件名乱码问题
        response.setHeader("content-disposition", "attachment;filename="+filename);
    
        //获取当前的真实物理路径(在服务器上的路径)
        String realPath = getServletContext().getRealPath("images/"+temp);
        //文件输入流
        FileInputStream fis = new FileInputStream(realPath);
        //文件输出流
        OutputStream os =response.getOutputStream();
        //缓冲数组
        byte[] buffer = new byte[1024];
        int len = 0;
        while((len=fis.read(buffer))>0){
            os.write(buffer, 0, len);
        }
        os.close();
        fis.close();
    }