setAttribute(String, object) – This method is used to save an object in session by assigning a unique string to the object. Later, the object can be accessed from the session by using the same String till the session is active.

The JSP container performance is improved by disabling the session in some of the JSPs. The server resource is utilized by session objects. A small amount of system resources is used by each session object as it is reside on the server. This causes increase in the traffic as the session ids are sent to the client.

How can we prevent implicit session creation in JSP? By default JSP page creates a session but sometimes we don’t need session in JSP page. We can use JSP page directive session attribute to indicate compiler to not create session by default. It’s default value is true and session is created.

JSP makes use of the servlet provided HttpSession Interface. This interface provides a way to identify a user across. The JSP engine exposes the HttpSession object to the JSP author through the implicit session object.

Session management is used to facilitate secure interactions between a user and some service or application and applies to a sequence of requests and responses associated with that particular user.

Sessions are a simple way to store data for individual users against a unique session ID. Session IDs are normally sent to the browser via session cookies and the ID is used to retrieve existing session data. The absence of an ID or session cookie lets PHP know to create a new session, and generate a new session ID.

There are four techniques used in Session tracking:

• Cookies.
• Hidden Form Field.
• URL Rewriting.
• HttpSession.

There are four main ways to manage Session in Java Web application written using Servlet and JSP.

• URL rewriting.
• Cookies.
• Hidden Form fields.
• HTTPS and SSL.

There are two types of session management – cookie-based and URL rewriting. These can be used independently or together. A web administrator uses session management to track the frequency of visits to a website and movement within the site.

Session Interface Methods

SessionFactory is a factory class for Session objects. It is available for the whole application while a Session is only available for particular transaction. Session is short-lived while SessionFactory objects are long-lived. SessionFactory provides a second level cache and Session provides a first level cache.

In hibernate, get() and load() are two methods which is used to fetch data for the given identifier. They both belong to Hibernate session class. Get() method return null, If no row is available in the session cache or the database for the given identifier whereas load() method throws object not found exception.

Both operations are used to implement changes in the persistence context, in the case of persist operation, it is used to insert a new entity into the context and there must not be another entity with the same ID, otherwise an exception will be thrown (EntityExistsException), the merge operation is used to insert an …

The EntityManager. persist() operation is used to insert a new object into the database. The state of the object at the point of the commit of the transaction will be persisted, not its state at the point of the persist call. persist should normally only be called on new objects.

So the merge method does exactly that: finds an entity instance by id taken from the passed object (either an existing entity instance from the persistence context is retrieved, or a new instance loaded from the database); copies fields from the passed object to this instance; returns newly updated instance.

Merge returns the managed instance that the state was merged to. It does return something what exists in PersistenceContext or creates a new instance of your entity. In any case, it will copy the state from the supplied entity, and return managed copy.

If your application no longer needs an EntityManagerFactory , you should close it to free these resources. When an EntityManagerFactory closes, all EntityManager s from that factory, and by extension all entities managed by those EntityManager s, become invalid.

The EntityManager. flush() operation can be used the write all changes to the database before the transaction is committed. This means that when you call persist, merge, or remove the database DML INSERT , UPDATE , DELETE is not executed, until commit, or until a flush is triggered.