 183 | Fields of persistable user defined classes (entity classes, embeddable classes and mapped ... and inverse fields) can be used in both entity classes and embeddable classes. However, the last two groups (primary key and version fields) can only be used in entity classes. Primary key fields |
182 | JPA Entity classes are user defined classes whose instances can be stored in a database. To store data in an ObjectDB database using JPA you have to define entity classes that represent your application data object model. This chapter explains how to define and use entity classes. |
179 | of the database. The persistence context serves as a cache of retrieved entity objects. If a requested entity object is not found in the persistence context a new object is constructed and filled with data that is retrieved from the database (or from the L2 cache - if enabled). The new entity object |
177 | Entity objects are in-memory instances of entity classes (persistable user defined classes ... requires using entity objects for many operations, including storing, retrieving, updating and deleting database objects. Entity Object Life Cycle The life cycle of entity objects consists of four states |
177 | Entity objects are in-memory instances of entity classes (persistable user defined classes ... requires using entity objects for many operations, including storing, retrieving, updating and deleting database objects. Entity Object Life Cycle The life cycle of entity objects consists of four states |
176 | New entity objects can be stored in the database either explicitly by invoking the persist method ... an instance of the Employee entity class in the database:
Employee employee = new Employee("Samuel ... and changes its state to Managed. The new entity object is stored in the database when the transaction |
175 | Detached entity objects are objects in a special state in which they are not managed by any EntityManager but still represent objects in the database. Compared to managed entity objects, detached ... that have been loaded before detachment should be used. Changes to detached entity objects are not stored in |
174 | Every EntityManager owns a persistence context, which is a collection of all the entity objects ... an entity object that is already managed by the EntityManager returns the existing instance from the persistence context, rather than a new instantiated entity object. The scope of the persistence context |
170 | Existing entity objects can be deleted from the database either explicitly by invoking the remove ... ();
The entity object is physically deleted from the database when the transaction is committed. Embedded objects that are contained in the entity object are also deleted. If the transaction is rolled |
169 | To be able to store Point objects in the database using JPA we need to define an entity class. A JPA entity class is a POJO (Plain Old Java Object) class, i.e. an ordinary Java class that is marked ... to serializable classes, which are marked as having the ability to be serialized. The Point Entity |