Cookie cookie = new Cookie(username,value);
cookie.setMaxAge(60*60*24*7,cookie);
response.addCookie(cookie);
在执行到 response.addCookie(cookie); 时 报错，发现在 cookie中保存的 username 变量是 英文时无问题，如果是中文则会出现以下异常～
严重: Servlet.service() for servlet [Login] in context with path [/learntest] threw exception
java.lang.IllegalArgumentException: Control character in cookie value or attribute.
at org.apache.tomcat.util.http.LegacyCookieProcessor.needsQuotes(LegacyCookieProcessor.java:431)
at org.apache.tomcat.util.http.LegacyCookieProcessor.generateHeader(LegacyCookieProcessor.java:303)
at org.apache.catalina.connector.Response.generateCookieString(Response.java:959)
at org.apache.catalina.connector.Response.addCookie(Response.java:907)
at org.apache.catalina.connector.ResponseFacade.addCookie(ResponseFacade.java:392)
at com.test.cookietest.Login.doPost(Login.java:74)
at com.test.cookietest.Login.doGet(Login.java:41)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1096)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:674)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2500)
at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2489)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)
原因（猜测）:
由于cookie 中只能以ASCII码的格式进行保存(即只能保存英文) 而在 Cookie.addCookie 方法中检查了 保存的文本内容 发现无法识别 抛出异常
解决方案:
在把变量保存到 cookie对象中之前 先 对 username 变量 使用 URLEncoder工具类 进行编码，使之以 unicode 编码格式进行保存
在提取 cookie 中 username 变量时 先使用 URLDecoder 工具类进行解码，使之以 utf-8 进行使用。
value = URLEncoder.encode(value, "utf-8");
Cookie cookie = new Cookie(username,value);
cookie.setMaxAge(60*60*24*7,cookie);
response.addCookie(cookie);
问题解决