• Servlet官方文檔

public HttpSessiongetSession(boolean create)
Returns the currentHttpSession associated with this request or, if if there is no current sessionand create is true, returns a new session.
If create is falseand the request has no valid HttpSession, this method returns null.
To make sure thesession is properly maintained, you must call this method before the responseis committed. If the container is using cookies to maintain session integrityand is asked to create a new session when the response is committed, anIllegalStateException is thrown.
Parameters: true -to create a new session for this request if necessary; false to return null ifthere's no current session
Returns: theHttpSession associated with this request or null if create is false and therequest has no valid session

翻譯意思：

getSession(boolean create)意思是返回當前reqeust中的HttpSession ，如果當前reqeust中的HttpSession 為null，當create為true，就創(chuàng)建一個新的Session，否則返回null；
簡而言之：
HttpServletRequest.getSession(ture)等同于 HttpServletRequest.getSession()
HttpServletRequest.getSession(false)等同于 如果當前Session沒有就為null；

原文地址：https://blog.csdn.net/earthchinagl/article/details/80523986