Inheritance Mapping We can map the inheritance hierarchy classes with the table of the database. There are several inheritance mapping strategies defined in the JPA specification : MappedSuperclass : the parent classes, can’t be entities Single Table : the entities from different classes with a common ancestor are placed in a single table Joined Table : […]
What Is Cascading ? Entity relationships often depend on the existence of another entity. Cascading is the way to achieve this. When we perform some action on the target entity, the same action will be applied to the associated entity. JPA Cascade Type All JPA-specific cascade operations are represented by the javax.persistence.CascadeType enum containing entries: ALL […]
hibernate dialects is a Java class available in org.hibernate.dialect package, which used to map Java Application with the database. If we need to interact with a database, we need to define the required database dialect in the hibernate configuration. Hibernate uses the dialect configuration to know which database is using in the App.
Why we use @GeneratedValue ? Hibernate supports different type of generation strategies to generate a primary key in the database table (MySQL / Oracle / PostgreSQL…). Using the annotation @GeneratedValue we can specifies how to generate values for the given column With @GeneratedValue annotation we have to set two parameters, strategy, and GenerationType. The GenerationType […]
JPA ASSOCIATIONS : Il existe plusieurs type d’associations entre entités :• One to One (1:1) -Unidirectionnelle / Bidirectionnelle• One to Many (1:N) -Unidirectionnelle / Bidirectionnelle• Many to One (N:1) -Unidirectionnelle / Bidirectionnelle• Many to Many (N:M) -Unidirectionnelle / Bidirectionnelle– TP : Mise en oeuvre des différentes associations JPA ASSOCIATIONS : • One To One entre […]
Why in “One to Many” Mapping hibernate data is getting inserted in child table while updating parent table ? Solution : You are using cascade = CascadeType.ALL in both @OneToMany mappings of your Sets. This means that whatever operation done on the parent entity, will be propagate also to the child entity That is when […]
If Hibernate does not insert element in child table , The reason is because the mapping does not cascade the persist operation. Example : The solution is : Cascade operations are extremely useful, but be mindful of their potential side effects, particularly if you modify Ticket which you don’t intend for an operation to be […]
(SOLVED) : “object references an unsaved transient instance – save the transient instance before flushing ” error
How to fix the Hibernate “object references an unsaved transient instance – save the transient instance before flushing” error ! SOLUTION : You should include on your collection mapping: (if using xml) or (if using annotations) This happens because you have a collection in your entity, and that collection has one or more items which […]
Request processing failed; nested exception is org.hibernate.HibernateException: No Session found for current thread Solution : If you have this exception using Hibernate , that mean that you forgot the annotation @Transaction in your service implement class function that caused this Exception.