Hibernate

Criteria is a simplified API for retrieving entities by composing Criterion objects. This is a very convenient approach for functionality like “search” screens where there is a variable number of conditions to be placed upon the result set. Example :

List employees = 

session.createCriteria(Employee.class)
                        .add(Restrictions.like("name", "a%") )
                        .add(Restrictions.like("address", "Boston"))
                        .addOrder(Order.asc("name") )
                        .list();

There are three types of inheritance models in Hibernate:

• Table per class hierarchy
• Table per subclass
• Table per concrete class

Three types of instance states:

• Transient -The instance is not associated with any persistence context
• Persistent -The instance is associated with a persistence context
• Detached -The instance was associated with a persistence context which has been closed – currently not associated

Automatic dirty checking is a feature that saves us the effort of explicitly asking Hibernate to update the database when we modify the state of an object inside a transaction.

By mapping the property with access=”field” in Hibernate metadata. This forces hibernate to bypass the setter method and access the instance variable directly while initializing a newly loaded object.