About object

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Manual
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Database Explorer

objects. The [Schema] window shows the user defined persistable types (entity and embeddable classes ... the approach of traditional visual database tools. Every row in the table represents a single object ... a single database object. This type of viewer is useful for viewing data of a simple object model. In
Manual
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SELECT clause (JPQL / Criteria API)

The ability to retrieve managed entity objects is a major advantage of JPQL. For example, the following query returns Country objects that become managed by the EntityManager em: TypedQuery ... > results = query.getResultList(); Because the results are managed entity objects they have all the support
Manual
22

CRUD Database Operations with JPA [2011-02-11]

Given an EntityManager, em, that represents a JPA connection to the object database, we can use it to store, retrieve, update and delete database objects. Storing New Entity Objects The following code fragment stores 1,000 Point objects in the database: em.getTransaction().begin(); for (int i
Manual
22

CRUD Database Operations with JPA

Given an EntityManager, em, that represents a JPA connection to the object database, we can use it to store, retrieve, update and delete database objects. Storing New Entity Objects The following code fragment stores 1,000 Point objects in the database: em.getTransaction().begin(); for (int i
Manual
21

Locking in JPA

in ObjectDB (and in JPA) is always at the database object level, i.e. each database object is locked separately. Optimistic locking is applied on transaction commit. Any database object ... is being performed on an old version of a database object, for which another update has already been committed
Manual
20

JPA Primary Key

Every entity object that is stored in the database has a primary key. Once assigned, the primary key cannot be modified. It represents the entity object as long as it exists in the database. As an object database, ObjectDB supports implicit object IDs, so an explicitly defined primary key is not
Manual
18

FROM clause (JPQL / Criteria API)

The FROM clause declares query identification variables that represent iteration over objects in ... a program, since both are used for iteration over objects. Range Variables Range variables are query identification variables that iterate over all the database objects of a specific entity class
Manual
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GROUP BY and HAVING clauses

properties of generated groups instead of individual objects and fields. The position of a GROUP BY ... 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
Manual
16

Shared (L2) Entity Cache

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
Manual
15

Paths and Types in JPQL and Criteria API

as arguments. Path expressions that navigate from one object to another. Instances of user defined ... ) and uses the dot (.) operator to navigate through persistent fields to other objects and values. For example - c.capital, where c represents a Country entity object uses the capital persistent field