java.sql.Connection and works as a factory for org.hibernate.Transaction. We should open session only when it’s required and close it as soon as we are done using it. Session object is the interface between java application code and hibernate framework and provide methods for CRUD operations.Session interface is primarily used by hibernate application. Session is light weight,short lived objects which are inexpensive to create and destroy. It allows you to create query objects to retrieve persistent objects.It wraps JDBC connection Factory for Transaction.It holds a mandatory (first-level) cache of persistent objects, used when navigating the object graph or looking up objects by identifier . ...
SessionFactory factory = cfg.buildSessionFactory();
Session session1 = factory.openSession();
Transaction tx=session2.beginTransaction();
Employee e1 = (Employee) session1.get(Employee.class, Integer.valueOf(101));
e1.setSalary(90000);
tx.commit();
session1.close();@ManyToMany annotation. It can either be unidirectional and bidirectional. In Unidirectional, the attributes model the association and you can use it to navigate it in your domain model or JPQL queries. The annotation tells Hibernate to map a Many-to-Many association. The bidirectional relationship, mapping allows you to navigate the association in both directions. Configuration config = new Configuration();
config.addResource("myinstance/configuration.hbm.xml");
config.setProperties( System.getProperties() );
SessionFactory sessions = config.buildSessionFactory();Session.save() method saves a record only if it’s unique with respect to its primary key and will fail to insert if primary key already exists in the table.Session.saveOrUpdate() method inserts a new record if primary key is unique and will update an existing record if primary key exists in the table already.createCriteria() method, which can be used to create a criteria object that returns instances of the persistence object’s class when your application executes a criteria query.hibernate.cfg.xml.Call EntityManager.createNativeQuery(String query)method.
Query q=em.createNativeQuery(“SELECT a.firstname,a.lastname”+”FROM Author a”);
Create hibernate.cfg.xml configuration file
Create Employee.hbm.xml mapping file
Create Employee.java source file and compile it.
Create ManageEmployee.java source file and compile it.
Execute ManageEmployee binary to run the program.SQLDialect, which contain the mapping between java language data type and database datatypes. There are many dialect classes for defining the RDBMS.Session s2=sf.openSession();
s2.beginTransaction();
a=(user)s2.get(user.class,102);
System.out.println(a);
s2.getTransaction().commit();
s2.close();Session.save() method is java.io.Serializable. It returns the newly generated identifier id value as a serializable object. While return type of the session.persist() method does not return anything. Serializable ser=session.save(object);markingmutable=false. The default value is true there which indicating that the class was not created by default.@Immutable annotation.get() :load() :session.lock() method is used to reattach a detached object to the session. session.lock() method does not check for any data synchronization between the database and the object in the persistence context and hence this reattachment might lead to loss of data synchronization. setMaxResults() the function works similar to LIMIT in SQL. Here, we set the maximum number of rows that we want to be returned. This method is implemented by all database drivers.setFetchSize() works for optimizing how Hibernate sends the result to the caller for example: are the results buffered, are they sent in different size chunks, etc. This method is not implemented by all the database drivers.createSQLQuery() method to let a developer call the native SQL statement directly and returns a Query object.Hibernate”. We don't want to use HQL-based features, instead, we want to write our own SQL queries. In this case, the code would be:Query query = session.createSQLQuery( "select * from interviewbit_employee ibe where ibe.fullName = :fullName")
.addEntity(InterviewBitEmployee.class)
.setParameter("fullName", "Hibernate"); //named parameters
List result = query.list();NamedQueries.getCurrentSession() method returns the session bound to the context and for this to work, you need to configure it in Hibernate configuration file. Since this session object belongs to the context of Hibernate, it is okay if you don’t close it. Once the SessionFactory is closed, this session object gets closed.openSession() method helps in opening a new session. You should close this session object once you are done with all the database operations. And also, you should open a new session for each request in a multi-threaded environment.save(), persist() or saveOrUpdate(). Persistent instances may be made transient by calling delete().get() or load() method is persistent.update(), saveOrUpdate(), lock() or replicate(). The state of a transient or detached instance may also be made persistent as a new persistent instance by calling merge().get() or load() methods. The method Class.newInstance() is used for this and it requires no-args constructor. So if you won’t have no-args constructor in entity beans, hibernate will fail to instantiate it and you will get HibernateException. <property name="hibernate.cache.use_query_cache">true</property>setCacheable(true) method of Query, quick example looks like below.Query query = session.createQuery("from Employee");
query.setCacheable(true);
query.setCacheRegion("ALL_EMP");sum(), min(), max() etc.createAlias(), setFetchMode() and setProjection()add() where we can add Restrictions.addOrder() method that we can use for ordering the results.<property name="hibernate.show_sql">true</property> beginTransaction() to start the transaction. This method returns the Transaction reference that we can use later on to either commit or rollback the transaction.DOMConfigurator or PropertyConfigurator. For web applications, you can use ServletContextListener to configure it.org.apache.log4j.Logger instance in the java classes and start logging.<property name="hibernate.connection.datasource">java:comp/env/jdbc/MyLocalDB</property> hibernate. cache. use_second_level_cache property to falseCACHEMODE.IGNOREorg.hibernate.cache.NoCacheProviderjava.util.set, java.util.Sortedset property in hibernate.java.util.List property in hibernate.java.util.Collection property in hibernate. java.util.Map property in hibernate.Session.beginTransaction method begins a unit of work and returns the associated Transaction object.