What is table per concrete class in hibernate?
In Table Per Concrete Class strategy a table is defined for each concrete class in the inheritance hierarchy to store all the attributes of that class and all of its superclasses. This strategy is optional in several ORM technologies (e.g. JPA), and querying root or branch classes can be very difficult and inefficient.
What is table per subclass in hibernate?
In case of table per subclass class, there will be three tables in the database, each representing a particular class. The joined-subclass subelement of class, specifies the subclass. The key sub-element of joined-subclass is used to generate the foreign key in the subclass mapped table.
What is the additional tag we have to use under table per class inheritance mapping hierarchy?
You need to use @Inheritance(strategy=InheritanceType. SINGLE_TABLE), @DiscriminatorColumn and @DiscriminatorValue annotations for mapping table per hierarchy strategy. In case of table per hierarchy, only one table is required to map the inheritance hierarchy.
Which tag in XML mapping will help us to map the table per concrete class inheritance strategy?
union-subclass”
“union-subclass” tag is used for each subclass definition to specify the Table per concrete class inheritance.
When table per concrete class is used three tables will be present?
Table Per Concrete class using xml file. In case of Table Per Concrete class, there will be three tables in the database having no relations to each other. There are two ways to map the table with table per concrete class strategy.
How many layers are available in hibernate architecture?
four layers
The Hibernate architecture is categorized in four layers. This is the high level architecture of Hibernate with mapping file and configuration file. Hibernate framework uses many objects such as session factory, session, transaction etc.
When the table per concrete class is used three tables will be present in the database which have no relationship between them?
In case of Table Per Concrete class, there will be three tables in the database having no relations to each other. There are two ways to map the table with table per concrete class strategy.
Can you tell something about table per class strategy?
Table Per Class strategy is the most logical inheritance solution because it mirrors the object model in the data model. In this pattern a table is defined for each class in the inheritance hierarchy to store only the local attributes of that class. All classes in the hierarchy must share the same id attribute.
What is true about table per class strategy?
Is it necessary to use Hibernate CFG XML for configuration in Hibernate?
Basically you are setting all the required properties via your properties object so there is no real need to tell Hibernate to look for a hibernate. cfg. xml file which is exactly what the configure() method does.
What is dirty checking in hibernate?
Hibernate monitors all persistent objects. At the end of a unit of work, it knows which objects have been modified. Then it calls update statement on all updated objects. This process of monitoring and updating only objects that have been changed is called automatic dirty checking in hibernate.
Is a session thread safe in hibernate?
No, Session object is not thread-safe in Hibernate and intended to be used with-in single thread in the application.
Can we create two SessionFactory in Hibernate?
Q. What we can create more than one sessionFactory in Hibernate. Ans And Its true We can create.As in my app i am able to da same.
Which classes will you use while working with hibernate?
Hibernate takes care of mapping Java classes to database tables using XML files and without writing any line of code. Provides simple APIs for storing and retrieving Java objects directly to and from the database. If there is change in the database or in any table, then you need to change the XML file properties only.
What is Mappedsuperclass?
A mapped superclass is a special type of class that is not persistent itself, but has subclasses that are persistent. A mapped superclass is useful for defined a common persistence superclass that defines common behavior across a set of classes, such as an id or version attribute.
What is @inheritance strategy InheritanceType SINGLE_TABLE?
The annotation @Inheritance is used on the root entity class with strategy = InheritanceType. SINGLE_TABLE . @DiscriminatorColumn is used on the root entity class to specify the discriminator column attributes. Discriminator is a way to differentiate rows belonging to different classes in the hierarchy.
What is table class mapping?
A class mapping describes how a class maps to the database. It typically controls the primary table for the class and how the class is linked to its superclass data, if any. For classes using datastore identity, the class mapping also manages the primary key column for the class.
What is @EntityListeners?
An entity listener is a stateless class with a no-arg constructor. An entity listener is defined by annotating the entity class with the @EntityListeners annotation: @Entity.
How to implement table per concrete class inheritance strategy in hibernate?
Where as Payment class is not considered to be as concrete class because with out Card or Cheque there is no existence of Payment. To implement the table per concrete class inheritance strategy in hibernate, we need to configure the all inheritance hierarchy classes in hbm.xml file.
How to store concrete class objects in separate tables in hibernate?
If we want to store each concrete class objects of inheritance in separate tables of database then we can go with table per concrete class strategy in hibernate. What is concrete class? In our example, we have 3 classes in the hierarchy called Payment, Card and Cheque. Here Card and Cheque classes are considered to be concrete classes.
What is table per class in hibernate?
Table per Class is one of the Hibernate inheritance strategy. As we discussed in the previous tutorial Types of Inheritance Mapping Strategies in Hibernate. In this tutorials, we are going to implement the Table per Class strategy in Hibernate using xml configuration.
How many nullable values are there in a concrete table?
In case of Table Per Concrete class, tables are created per class. So there are no nullable values in the table. Disadvantage of this approach is that duplicate columns are created in the subclass tables.