1- Configuration class – includes 2 things
(i)Database connection- Using either .cfg or .properties file.
(ii)mapping – connection between java classes to database tables using either .hbm files or annotations.
- Object of Session is created each time when any operation is required.
- Session objects are used to create physical connection with database.
- Session is thread-safe, so many threads can execute it simultaneously.
- Session holds a mandatory (first-level) cache of saved java objects in database.
- Session wraps JDBC connection for Transaction(actual db interaction).
- Object of SessionFactory should be created only once per database.
- SessionFactory is used to create session objects.
4- Transaction Interface-
- Transaction represents unit of work with database OR Transaction is actual interaction with database to perform operations defined on session.
- Transaction is associated with session.
- Query is used to create manual queries(hql/sql).
- Criteria is used to apply conditions.