How to check whether the session is existed?

By mkyong | Updated: August 30, 2012

Viewed: 2,244 (+22 pv/w)

Tags: servlet session

There are two ways to detect whether the session is existed.

1) request.getSession(); + session.isNew()

– Retrieve a session from “request.getSession();”, this function will always return a session no matter what, it’s equivalent to request.getSession(true);. The only problem is you do not know whether this is new or existed session.
– Later you can check with “session.isNew()”, true if this is a new session else return an existed session.

public void doGet(HttpServletRequest request, HttpServletResponse response)
	throws IOException{

		response.setContentType("text/html");
		PrintWriter pw = response.getWriter();

		HttpSession session = request.getSession();
		if(session.isNew()){
			pw.println("New session is jutst created");
		}else{
			pw.println("This is old session");
		}	
	}

2) request.getSession(false); + if(session ==null)

– Retrieve a session from “request.getSession(false);”, this function will return a session if existed , else a null value will return.
– Later you can do a “null” checking with the session object, null means no existed session available.

public void doGet(HttpServletRequest request, HttpServletResponse response)
	throws IOException{
	
		response.setContentType("text/html");
		PrintWriter pw = response.getWriter();
		
		HttpSession session = request.getSession(false);
		if(session ==null){
			pw.println("No session available");
		}else{
			pw.println("This is old session");
		}	
	}