The JSP Files (part 6): State Of Grace - ...And Read
( Page 5 of 9 )

So that takes care of writing a cookie - but how about reading it? Here's the code.

<%
// declare some variables
Cookie cookieCounter = null;

// the cookie you want
String cookieName = "counter";
int cookieFound = 0;

// a few more useful variables
String tempString;
int count=0;

// get an array of all cookies available on client
Cookie[] cookies = request.getCookies();

// iterate through array looking for your cookie
for(int i=0; i<cookies.length; i++)
{
    cookieCounter = cookies[i];
    if (cookieName.equals(cookieCounter.getName()))
	{
	cookieFound = 1;
  	break;
	}

}
%>

Before you can read the cookie, you need to find it on the client's hard drive. Since JSP does not currently allow you to directly locate and identify the cookie by name, you need to iterate through all available cookies until you find the one you're looking for. In the example above, the "for" loop does just that; if and when it finds the cookie, it sets the "cookieFound" variable to 1 and breaks out of the loop.

At this point, the cookie is stored in the Cookie object "cookieCounter". You can then use the getValue() object method to get the current value of the cookie variable, and use it in your script.

<%
// if found
if(cookieFound == 1)
{

	// get the counter value as string
	tempString = cookieCounter.getValue();

	// convert it to a number
	count = Integer.parseInt(tempString);

	// increment it
	count++;

	// back to a string
	tempString = Integer.toString(count);

	// store it in the cookie for future use
	cookieCounter.setValue(tempString);

	// set some other attributes
	cookieCounter.setMaxAge(300);
	cookieCounter.setPath("/");

	// send cookie to client
	response.addCookie(cookieCounter);
}
%>

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