ObjectDB Database Search

Fields of persistable user defined classes ( entity classes, embeddable classes and mapped ... , persistent 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

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

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

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

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 ... its state to Managed. The new entity object is stored in the database when the transaction

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 newly instantiated entity object. The scope of the persistence

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 ... Entity Class The following Point class, which represents points in the plane, is marked as an entity

Existing entity objects can be deleted from the database either explicitly by invoking the remove ... ); em. getTransaction (). begin (); em. remove (employee); em. getTransaction (). commit (); The entity ... that are contained in the entity object are also deleted. If the transaction is rolled back and not

Modifying existing entity objects that are stored in the database is based on transparent ... Once an entity object is retrieved from the database (no matter which way) it can simply be modified in memory ... (); The entity object is physically updated in the database when the transaction is committed

The element specifies settings of the two cache mechanisms for entities : The ref attribute specifies the reference type for holding non dirty entities in the persistence context of the EntityManager ... entities are always held by strong references in the persistence context (until commit or flush

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.  This chapter contains the following sections:

To store objects in an ObjectDB database using JPA we need to define an entity class: Open the [New Entity Class] dialog box, e.g. by right clicking the project node (in the [Projects] window) and selecting New Entity Class ... (or New Other... Persistence Entity Class and clicking Next ). Enter

To store objects in an ObjectDB database using JPA we need to define an entity class: Open the [New Entity Class] dialog box, e.g. by right clicking the project node (in the [Projects] window) and selecting  New Entity Class ... (or  New Other... Persistence Entity Class and clicking

. ObjectDB supports all the JPA persistable types, which are: User defined classes - Entity classes ... types and Serializable types (user or system defined). Note : Only instances of entity classes can be stored in the database directly. Other persistable types can be embedded in entity classes as fields

To store objects in an ObjectDB database using JPA we need to define an entity class: Right click ...   Finish to create the new entity class. A new class that should represent  Guest objects in ... java.io.Serializable; import java.sql.Date; import javax.persistence. Entity ; import javax.persistence

To store objects in an ObjectDB database using JPA we need to define an entity class: Open ... .Serializable; import java.sql.Date; import javax.persistence. Entity ; import javax.persistence.GeneratedValue; import javax.persistence.Id; @ Entity public class Guest implements Serializable { private

To store objects in an ObjectDB database using JPA we need to define an entity class: Open ... .Serializable; import javax.persistence.*; @ Entity public class Point implements Serializable { private ... objects in the database. Besides the @ Entity annotation and the id field (and its annotations

To store objects in an ObjectDB database using JPA we need to define an entity class: Open ... code: package guest; import java.io.Serializable; import java.sql.Date; import javax.persistence. Entity ; import javax.persistence.GeneratedValue; import javax.persistence.Id; @ Entity public class Guest

To store objects in an ObjectDB database using JPA we need to define an entity class: Right click ... ; import java.io.Serializable; import javax.persistence.*; @ Entity public class Point implements ... should represent Point objects in the database. Apart from the @ Entity annotation and the id field

To store objects in an ObjectDB database using JPA we need to define an entity class: Open ... .Serializable; import java.sql.Date; import javax.persistence. Entity ; import javax.persistence.GeneratedValue; import javax.persistence.Id; @ Entity public class Guest implements Serializable { private

Callback methods are user defined methods that are attached to entity lifecycle events ... methods are methods that are defined within an entity class. For example, the following entity class defines all the supported callback methods with empty implementations: @ Entity public static class

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 ... that is absent from other object oriented databases. Entity Identification Every entity object in

of bookmarked entity objects. The [Schema] window shows the user defined persistable types ( entity ... ] tabbed window or select an element for viewing (an entity class in the [Schema] tabbed window ... ). An entity object can be specified by type and primary key separated by # (e.g. Point#1). A collection

The ability to retrieve managed entity objects is a major advantage of JPQL. For example ... (); Because the results are managed entity objects they have all the support that JPA provides for managed entity objects, including transparent navigation to other database objects, transparent update

Querying without indexes requires iteration over entity objects in the database one by one. This may take a significant amount of time if many entity objects have to be examined. Using proper ... which fields to define with indexes should be done carefully. Single Field Index The following entity

Modifications to entity classes that do not change their persistent field definitions ... of an entity class are detected by ObjectDB. New entity objects have to be stored in the new class schema, and old entity objects, which were stored previously in the old class schema

Instances of user defined persistable classes ( entity classes, mapped super classes and embeddable ... and values. For example - c.capital , where c represents a Country entity object uses the capital persistent field in the Country class to navigate to the associated Capital entity object. Path expression

, if they happen, are detected earlier. Optimistic Locking ObjectDB maintains a version number for every entity object. The initial version of a new entity object (when it is stored in the database for the first time) is 1. In every transaction in which an entity object is modified its version number

JPA Method in javax.persistence.EntityManager void refresh (   Object  entity ,  ... the state of the instance from the database, overwriting changes made to the entity , if any, and lock ... is pessimistic and the entity instance is found but cannot be locked: the PessimisticLockException will be thrown

JPA Method in javax.persistence.EntityManager void refresh (   Object  entity ,  ... , overwriting changes made to the entity , if any, and lock it with respect to given lock mode type. If the lock mode type is pessimistic and the entity instance is found but cannot be locked

JPA Method in javax.persistence.EntityManager void detach (   Object  entity ) Remove the given entity from the persistence context, causing a managed entity to become detached. Unflushed changes made to the entity if any (including removal of the entity ), will not be synchronized

JPA Method in javax.persistence.EntityManager void lock (   Object  entity ,     LockModeType  lockMode,    Map  properties ) Lock an entity ... and with specified properties. If a pessimistic lock mode type is specified and the entity contains a version

JPA Method in javax.persistence.EntityManager void lock (   Object  entity ,     LockModeType  lockMode ) Lock an entity instance that is contained in ... and the entity contains a version attribute, the persistence provider must also perform optimistic version

JPA Method in javax.persistence.EntityManager void refresh (   Object  entity ,  ... the specified properties, and overwriting changes made to the entity , if any. If a vendor-specific property or hint is not recognized, it is silently ignored. Parameters: entity - entity instance

JPA Method in javax.persistence.EntityManager void refresh (   Object  entity ) Refresh the state of the instance from the database, overwriting changes made to the entity , if any. Parameters: entity - entity instance Throws: IllegalArgumentException - if the instance is not

; entity ) Return the id of the entity . A generated id is not guaranteed to be available until after the database insert has occurred. Returns null if the entity does not yet have an id. Parameters: entity - entity instance Return: id of the entity Throws: IllegalArgumentException - if the object is found not to be an entity Since: JPA 2.0

; entity ) Create and add a query root corresponding to the entity that is the target of the delete. A CriteriaDelete object has a single root, the entity that is being deleted. Parameters: entity - metamodel entity representing the entity of type X Return: query root corresponding to the given entity Since: JPA 2.1

; entity ) Determine the load state of an entity belonging to the persistence unit. This method can be used to determine the load state of an entity passed as a reference. An entity is considered loaded ... to unintended loading of state. Parameters: entity - entity instance whose load state

JPA Method in javax.persistence.EntityManager T merge (   T  entity ) Merge the state of the given entity into the current persistence context. Parameters: entity - entity instance ... - if instance is not an entity or is a removed entity TransactionRequiredException - if there is no transaction

JPA Method in javax.persistence.EntityManager void persist (   Object  entity ) Make an instance managed and persistent. Parameters: entity - entity instance Throws: EntityExistsException - if the entity already exists. (If the entity already exists, the EntityExistsException

JPA Method in javax.persistence.EntityManager void remove (   Object  entity ) Remove the entity instance. Parameters: entity - entity instance Throws: IllegalArgumentException - if the instance is not an entity or is a detached entity TransactionRequiredException - if invoked

; entity ) Create and add a query root corresponding to the entity that is the target of the update. A CriteriaUpdate object has a single root, the entity that is being updated. Parameters: entity - metamodel entity representing the entity of type X Return: query root corresponding to the given entity Since: JPA 2.1

JPA Annotation Entity Target: TYPE Implemented Interfaces: Annotation Specifies that the class is an entity . This annotation is applied to the entity class. Since: JPA 1.0 The JPA Persistable Types article explains how to use Entity . Public Annotation Attributes String name default "" (Optional

JPA Method in javax.persistence.metamodel.Metamodel EntityType entity (   Class  cls ) Return the metamodel entity type representing the entity . Parameters: cls - the type of the represented entity Return: the metamodel entity type Throws: IllegalArgumentException - if not an entity Since: JPA 2.0

JPA Method in javax.persistence.PersistenceUtil boolean isLoaded (   Object  entity ) Determine the load state of an entity . This method can be used to determine the load state of an entity passed as a reference. An entity is considered loaded if all attributes for which FetchType

JPA Method in javax.persistence.EntityManager boolean contains (   Object  entity ) Check if the instance is a managed entity instance belonging to the current persistence context. Parameters: entity - entity instance Return: boolean indicating if entity is in persistence context

; entity ) Create and add a query root corresponding to the given entity , forming a cartesian product with any existing roots. Parameters: entity - metamodel entity representing the entity of type X Return: query root corresponding to the given entity Since: JPA 2.0

; entity ) Get the current lock mode for the entity instance. Parameters: entity - entity instance Return: lock mode Throws: TransactionRequiredException - if there is no transaction or if the entity ... is not a managed entity and a transaction is active Since: JPA 2.0

; entity ,    String attributeName ) Determine the load state of a given persistent attribute of an entity belonging to the persistence unit. Parameters: entity - entity instance ... : false if entity's state has not been loaded or if the attribute state has not been loaded, else true Since: JPA 2.0

JPA Constructor in javax.persistence.PessimisticLockException PessimisticLockException (   String message,    Throwable cause,    Object  entity ... , and entity . Parameters: message - the detail message. cause - the cause. entity - the entity . Since: JPA 2.0