code: public static void toWriter(String templateFileName, javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) {
  		final VelocityContext context = new VelocityContext();
  		parseRequest(context, request);
  		parseSession(context, request.getSession(false));
  
  		Writer writer = null;
  		try {
  			writer = response.getWriter();
  			toWriter(templateFileName, context, writer);
  		} catch (Exception e) {
  			throw new UtilException(e, "Write Velocity content template by [{}] to response error!", templateFileName);
  		} finally {
  			IoUtil.close(writer);
  		}
  	}
docs: 生成内容写到响应内容中<br>
  模板的变量来自于Request的Attribute对象
  
  @param templateFileName 模板文件
  @param request 请求对象，用于获取模板中的变量值
  @param response 响应对象