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Manual
23

JPA Entity Fields

otherwise (e.g. by using the @Transient annotation). Storing an entity object in the database does not ... . When an entity object is stored in the database every persistent field must contain either null or a value ... in the database for the first time) is 1. For every transaction in which an entity object
Manual
21

Defining a JPA Entity Class

To be able to store Point objects in the database using JPA we need to define an entity class ... (annotated) as having the ability to represent objects in the database. Conceptually this is similar ... , and accordingly, provides the ability to store Point objects in the database and retrieve Point
Manual
21

Shared (L2) Entity Cache

the database and added to the shared cache. On commit - new and modified entity objects are added ... 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
Manual
20

Running JPA Queries

(with getResultList) The following query retrieves all the Country objects in the database. Because multiple ... object reflecting the number of Country objects in the database: TypedQuery query = em ... on the database content. For example, the following query is expected to return a single Country object
Manual
20

JPA Persistable Types

class can only be stored in the database as embedded objects, i.e. as part of a containing entity ... The term persistable types refers to data types that can be used in storing data in the database ... can be stored in the database directly. Other persistable types can be embedded in entity classes as fields. In
Tutorial
20

Step 3: Add a Main Class

= emf.createEntityManager(); // Store 1000 Point objects in the database: em ... (); // Find the number of Point objects in the database: Query q1 = em.createQuery("SELECT COUNT(p ... objects from the database: TypedQuery query = em.createQuery("SELECT p
Tutorial
20

Step 3: Add a Main Class

to store Point objects in the database and then retrieve them from the database. Use copy and paste ... Point objects in the database: em.getTransaction().begin(); for (int i = 0; i ... ); } em.getTransaction().commit(); // Find the number of Point objects in the database
Manual
19

UPDATE SET Queries in JPA/JPQL

the content of specified entity objects in the database. Updating entity objects in the database using ... with the database. For example, the EntityManager may not be aware that a cached entity object in ... Existing entity objects can be updated, as explained in chapter 2, by: Retrieving the entity
Manual
19

GROUP BY and HAVING clauses

clause. When a GROUP BY clause exists in a JPQL query, database objects (or tuples of database objects ... over all the Country objects in the database. The GROUP BY clause groups these Country objects by ... properties of generated groups instead of individual objects and fields. The position of a GROUP BY
Manual
18

JPA Query Structure (JPQL / Criteria)

rather than just field values from database tables, as with SQL. That makes JPQL more object oriented friendly ... JPQL Query The following query retrieves all the Country objects in the database: SELECT c FROM ... over objects in the database. A query variable that is bound to an entity class is referred to as