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javax.persistence Interface EntityManager Interface used to interact with the persistence context. An EntityManager instance is associated with a persistence context. A persistence context is a set ... . The EntityManager API is used to create and remove persistent entity instances, to find entities by their primary


Method javax.persistence.EntityManager T unwrap( Class<T> cls ) Return an object of the specified type to allow access to the provider-specific API. If the provider's EntityManager implementation ... of the object to be returned. This is normally either the underlying EntityManager implementation


Method javax.persistence.EntityManager Object getDelegate() Return the underlying provider object for the EntityManager, if available. The result of this method is implementation specific. The unwrap method is to be preferred for new applications. Returns: underlying provider object for EntityManager Since: JPA 1.0

Obtaining a JPA Database Connection

In JPA a database connection is represented by the EntityManager interface. Therefore, in order to manipulate an ObjectDB database we need an EntityManager instance. Operations that modify database ... an EntityManager instance consists of two steps. First we need to obtain an instance

refresh(entity, lockMode, properties)

Method javax.persistence.EntityManager void refresh( Object entity, LockModeType lockMode, Map<String,Object> properties ) Refresh the state of the instance from the database, overwriting changes ... EntityManager instance with PersistenceContextType.TRANSACTION or with a lock mode

refresh(entity, lockMode)

Method javax.persistence.EntityManager void refresh( Object entity, LockModeType lockMode ) Refresh the state of the instance from the database, overwriting changes made to the entity, if any ... -managed EntityManager instance with PersistenceContextType.TRANSACTION or with a lock mode


Method javax.persistence.EntityManager void close() Close an application-managed entity manager. After the close method has been invoked, all methods on the EntityManager instance and any Query and TypedQuery objects obtained from it will throw the IllegalStateException except for getProperties


Method javax.persistence.EntityManager Query createQuery( String qlString ) Create an instance of Query for executing a Java Persistence query language statement. Parameters: qlString - a Java Persistence query string Returns: the new query instance Throws: IllegalArgumentException - if the query string is found to be invalid Since: JPA 1.0

find(entityClass, primaryKey, lockMode, properties)

Method javax.persistence.EntityManager T find( Class<T> entityClass, Object primaryKey, LockModeType lockMode, Map<String,Object> properties ) Find by primary key and lock, using the specified properties. Search for an entity of the specified class and primary key and lock it with respect


Method javax.persistence.EntityManager CriteriaBuilder getCriteriaBuilder() Return an instance of CriteriaBuilder for the creation of CriteriaQuery objects. Returns: CriteriaBuilder instance Throws: IllegalStateException - if the entity manager has been closed Since: JPA 2.0

Getting Started

ObjectDB is very easy to use. Follow the Getting Started Tutorial and the Quick Tour manual chapter and in minutes you may be able to write and run first Java programs against ObjectDB.

Prior knowledge or experience in database programming (SQL, JDBC, ORM, JPA, etc.) is not required, but some background in using the Java language is essential.

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