删除Cookie的两个步骤

引用

Sets the maximum age of the cookie in seconds. 
A positive value indicates that the cookie will expire after that many seconds have passed. Note that the value is the maximum age when the cookie will expire, not the cookie's current age. 

A negative value means that the cookie is not stored persistently and will be deleted when the Web browser exits. A zero value causes the cookie to be deleted. 

By default, -1 indicating the cookie will persist until browser shutdown. 

以上是javax.servlet.http.Cookie类的setMaxAge(int expire)方法的API文档里的描述。 

一开始我以为只要将cookie的maxAge设置为0就行了，但调试项目发现设置maxAge为0的cookie并没有删除，而是还能得到。 
原来除了第一步cookie.setMaxAge(0);之外，还需要有一个步骤，那就是response.addCookie(cookie);作用是将此修改后的cookie返回给浏览器。