Session tracking In Java

SESSION
TRACKING
HoneyGurnaniM.EComputer
Prof Honey Gurnani
I/C Computer Department
Tolani FG Polytechnic

WHAT IS SESSION
 Session simply means a particular interval of time.
 A series of related interactions between a single client
and web server over a period of time.
WHAT IS SESSION TRACKING
 A way to maintain state (data) of an user. It is also
known as session management in servlet.
 Tracking data among request in a session.

HTTP PROTOCOL & SESSION TRACKING
 Http protocol is a stateless so we need to maintain
state using session tracking techniques.
 Each time user requests to the server, server treats
the request as the new request.
 So we need to maintain the state of an user to
recognize to particular user.
 In many cases, information has to be saved for the
future purpose or for some reference.
 Session provides such mechanism

SESSION TRACKING TECHNIQUES
There are four techniques used in Session tracking:
 HttpSession
 Cookies
 Hidden Form Field
 URL Rewriting

MAINTAINING SESSION THROUGH SESSION
TRACKING API -: HTTPSESSION INTERFACE
 In such case, container creates a session id for
each user.
 The container uses this id to identify the particular
user.
 An object of HttpSession can be used to perform
two tasks:
1. bind objects
2. view and manipulate information about a session,
such as the session identifier, creation time, and
last accessed time.

HOW TO GET THE HTTPSESSION OBJECT ?
 public HttpSession getSession():Returns the
current session associated with this request, or if
the request does not have a session, creates one.
 public HttpSession getSession(boolean
create):Returns the current HttpSession associated
with this request or, if there is no current session
and create is true, returns a new session.

METHODS OF HTTPSESSION INTERFACE
 public String getId():Returns a string containing
the unique identifier value.
 public long getCreationTime():Returns the time
when this session was created, measured in
milliseconds since midnight January 1, 1970 GMT.
 public long getLastAccessedTime():Returns the
last time the client sent a request associated with
this session, as the number of milliseconds since
midnight January 1, 1970 GMT.
 public void invalidate():Invalidates this session
then unbinds any objects bound to it.

ADVANTAGES OF HTTP SESSIONS IN
SERVLET
 Any kind of object can be stored into a session, be
it a text, database, dataset etc.
 Usage of sessions is not dependent on the client’s
browser.
 Sessions are secure and transparent

MAINTAINING SESSION THROUGH COOKIES
 A cookie is a small piece of information that is
persisted between the multiple client requests.
 A cookie has a name, a single value, and optional
attributes such as a comment, path and domain
qualifiers, a maximum age, and a version number.

WORKING OF COOKIE
 By default, each request is considered as a new
request.
 In cookies technique, we add cookie with response
from the servlet.
 So cookie is stored in the cache of the browser.
 After that if request is sent by the user, cookie is
added with request by default.
 Thus, we recognize the user as the old user.

TYPES OF COOKIES
 There are 2 types of cookies in servlets.
Non-persistent cookie
Persistent cookie
 Non-persistent cookie
It is valid for single session only. It is removed each
time when user closes the browser.
 Persistent cookie
It is valid for multiple session . It is not removed
each time when user closes the browser. It is
removed only if user logout or signout.

ADVANTAGE OF COOKIES
 Simplest technique of maintaining the state.
 Cookies are maintained at client side.

DISADVANTAGE OF COOKIES
 It will not work if cookie is disabled from the
browser.
 Only textual information can be set in Cookie
object.

COOKIE CLASS
 javax.servlet.http.Cookie class provides the
functionality of using cookies. It provides a lot of
useful methods for cookies.
 Cookie Constructor
Constructor Description
Cookie() Constructs a cookie.
Cookie(String name, String value) Constructs a cookie with a specified
name and value.

METHODS OF COOKIES
Method Description
public void setMaxAge(int expiry) Sets the maximum age of the cookie
in seconds.
public String getName() Returns the name of the cookie. The
name cannot be changed after
creation.
public String getValue() Returns the value of the cookie.
public void setName(String name) changes the name of the cookie.
public void setValue(String value) changes the value of the cookie.

HIDDEN FIELD
 A hidden (invisible) textfield is used for
maintaining the state of an user.
 Store the information in the hidden field and get it
from another servlet.
 This approach is better if we have to submit form in
all the pages and we don't want to depend on the
browser.

REAL APPLICATION OF HIDDEN FORM FIELD
 It is widely used in comment form of a website. In
such case, we store page id or page name in the
hidden field so that each page can be uniquely
identified.

ADVANTAGE OF HIDDEN FORM FIELD
 It will always work whether cookie is disabled or
not.

DISADVANTAGE OF HIDDEN FORM FIELD:
 It is maintained at server side.
 Extra form submission is required on each pages.
 Only textual information can be used.

URL REWRITING
 In URL rewriting, we append a token or identifier to
the URL of the next Servlet or the next resource.
 url?name1=value1&name2=value2&??
 A name and a value is separated using an equal =
sign, a parameter name/value pair is separated
from another parameter using the ampersand(&).
 When the user clicks the hyperlink, the parameter
name/value pairs will be passed to the server.
 From a Servlet, we can use getParameter() method
to obtain a parameter value.

ADVANTAGE OF URL REWRITING
 It will always work whether cookie is disabled or not
(browser independent).
 Extra form submission is not required on each
pages.

DISADVANTAGE OF URL REWRITING
 It will work only with links.
 It can send Only textual information.

THANKYOU

Session tracking In Java

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