1、 问题描述
Servlet中执行下面一段代码:
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8");
System.out.println( new Date().toString()); Cookie cookie = new Cookie("lasttime", new Date().toString());
response.addCookie(cookie); String s = "欢迎您首次访问该网站!~";
Cookie[] cookies = request.getCookies();
if (cookies != null)
for (Cookie cs : cookies) {
if (cs.getName().equals("lasttime")) {
s = "您上次登录的时间为:" + cs.getValue().replace("-", " ");
}
} response.getWriter().print(s);
}
抛出如下异常:
2、 追根溯源
出现上述问题觉得很奇怪,因为程序编译通过,至少证明没有语法错误,根据编译器提示,定位问题到:
Cookie cookie = new Cookie("lasttime", new Date().toString());
response.addCookie(cookie);
查看JAVAEE-API,发现有如下
回过去看代码,发现
输入: System.out.println( new Date().toString());
输出: Fri Apr 20 21:56:39 CST 2018
很明显输出字符串中存在 空格 ,所以程序会报错,存在无效字符。
3、解决方案
解决问题的方法其实很简单,只要字符串中不存在空格即可成功,下面将给出几种具体的解决办法,程序修改如下:
法一
思路:用“-”代替“ ”,之后记得换回来即可,程序成功运行。 public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8");
System.out.println( new Date().toString()); Cookie cookie = new Cookie("lasttime", new Date().toString().replace(" ", "-"));
cookie.setMaxAge(60*60);
response.addCookie(cookie); String s = "欢迎您首次访问该网站!~";
Cookie[] cookies = request.getCookies();
if (cookies != null)
for (Cookie cs : cookies) {
if (cs.getName().equals("lasttime")) {
s = "您上次登录的时间为:" + cs.getValue().replace("-", " ");
}
} response.getWriter().print(s);
}
法二
思路:进行URL编码,然后把编码后的字符串放到Cookie中,之后进行URL解码即可。 public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8");
System.out.println( new Date().toString()); Cookie cookie = new Cookie("lasttime", URLEncoder.encode(new Date().toString(), "UTF-8"));
cookie.setMaxAge(*);
response.addCookie(cookie); String s = "欢迎您首次访问该网站!~";
Cookie[] cookies = request.getCookies();
if (cookies != null)
for (Cookie cs : cookies) {
if (cs.getName().equals("lasttime")) {
s = "您上次登录的时间为:" + URLDecoder.decode(cs.getValue(), "UTF-8");
}
}
response.getWriter().print(s);
}
程序运行正常,符合预期值。