初学Java Web，看的是明日科技的《Java Web从入门到精通》，其中第六章 JSP内置对象 6.2.3节 获取cookie 有一个例子：
通过cookie保存并读取用户登录信息：
index.jsp 代码如下
<%@ page language="java" contentType="text/html; charset=utf-8"pageEncoding="utf-8"%><%@ page import="java.net.URLDecoder" %><html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><title>通过cookie保存并读取用户登录信息</title></head><body><%Cookie[] cookies = request.getCookies();//从request中获得Cookie对象的集合String user = ""; //登录用户String date = ""; //注册的时间if (cookies != null) {for (int i = 0; i < cookies.length; i++) { //遍历cookie对象的集合if (cookies[i].getName().equals("mrCookie")) {//如果cookie对象的名称为mrCookieuser = URLDecoder.decode(cookies[i].getValue().split("#")[0]);//获取用户名date = cookies[i].getValue().split("#")[1];//获取注册时间}}}if ("".equals(user) && "".equals(date)) {//如果没有注册%>游客您好，欢迎您初次光临！<form action="deal.jsp" method="post">请输入姓名：<input name="user" type="text" value=""><input type="submit" value="确定"></form><%} else {//已经注册%>欢迎[<b><%=user %></b>]再次光临<br>您注册的时间是：<%=date %><%}%></body></html>
deal.jsp 代码如下：
<%@ page language="java" contentType="text/html; charset=utf-8"pageEncoding="utf-8"%><%@ page import="java.net.URLEncoder" %><html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><title>写入cookie</title><script type="text/javascript">window.location.href="index.jsp"</script></head><body><%request.setCharacterEncoding("utf-8");String user=URLEncoder.encode(request.getParameter("user"),"utf-8"); //获取用户名Cookie cookie = new Cookie("mrCookie", user+"#"+new java.util.Date().toLocaleString());cookie.setMaxAge(60*60*24*30); //设置cookie有效期30天response.addCookie(cookie); //保存cookie%></body></html>
在用Eclipse编译运行的时候，报错：
Type Exception Report
Message An exception occurred processing JSP page [/deal.jsp] at line [17]
Description The server encountered an unexpected condition that prevented it from fulfilling the request.
Exception
org.apache.jasper.JasperException: An exception occurred processing JSP page [/deal.jsp] at line [17]
14: String user=URLEncoder.encode(request.getParameter("user"),"utf-8"); //鑾峰彇鐢ㄦ埛鍚�
15: Cookie cookie = new Cookie("mrCookie", user+"#"+new java.util.Date().toLocaleString());
16: cookie.setMaxAge(60*60*24*30); //璁剧疆cookie鏈夋晥鏈�30澶�
17: response.addCookie(cookie); //淇濆瓨cookie
18: %>
19:
20: </body>
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:588)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:481)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
Root Cause
java.lang.IllegalArgumentException: An invalid character [32] was present in the Cookie value org.apache.tomcat.util.http.Rfc6265CookieProcessor.validateCookieValue(Rfc6265CookieProcessor.java:182) org.apache.tomcat.util.http.Rfc6265CookieProcessor.generateHeader(Rfc6265CookieProcessor.java:115) org.apache.catalina.connector.Response.generateCookieString(Response.java:1010) org.apache.catalina.connector.Response.addCookie(Response.java:962) org.apache.catalina.connector.ResponseFacade.addCookie(ResponseFacade.java:385) org.apache.jsp.deal_jsp._jspService(deal_jsp.java:126) org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) javax.servlet.http.HttpServlet.service(HttpServlet.java:741) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:443) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329) javax.servlet.http.HttpServlet.service(HttpServlet.java:741) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
求助搜索，了解到 An invalid character [32] was present in the Cookie value 中32对应的编码是空格，Stack Overflow上的回答：This is due to Tomcat's cookie processing being changed to a RFC 6265 compliant implementation by default in 8.5, which does not allow space (character 32), among others. 我的tomcat版本是9.0，然而知道是空格的原因，但并不清楚是哪里产生了空格，逐条语句分析后，怀疑 new java.util.Date().toLocaleString()这句中有空格输出，使用控制台打印System.out.println(new java.util.Date().toLocaleString()), 输出值确实有空格，改用新的方式输入时间，避免出现空格。
修改后的deal.jsp代码：
<%@ page language="java" contentType="text/html; charset=utf-8"pageEncoding="utf-8"%><%@ page import="java.net.URLEncoder,java.util.*,java.text.*" %><html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><title>写入cookie</title><script type="text/javascript">window.location.href="index.jsp"</script><body><%request.setCharacterEncoding("utf-8");Date date = new Date();SimpleDateFormat dtf = new SimpleDateFormat("h:m:s");String user=URLEncoder.encode(request.getParameter("user"),"utf-8"); //从“user"获取用户名Cookie cookie = new Cookie("mrCookie", user+"#"+dtf.format(date));System.out.println(dtf.format(date));cookie.setMaxAge(60*60*24*30); //设置cookie有效期30天response.addCookie(cookie); //保存cookie%></body></html>
再次运行，输入用户名mr后，正常显示。
结论：println真的好用。