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11

Query Parameters in JPA

getCountryByName(EntityManager em, String name) { TypedQuery<Country> query = em.createQuery ... Country getCountryByName(EntityManager em, String name) { TypedQuery<Country> query = em ... without parameters: public Country getCountryByName(EntityManager em, String name) { TypedQuery
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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 ... are not associated with an EntityManager and changes to them when a transaction is active are not
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ObjectDB Object Database Features

entity object cache (per EntityManager). L2 shared entity data cache (per EntityManagerFactory ... and fault tolerance. Online Backup Online backup by a simple query on an EntityManager
9

Entity Management Settings

the persistence context of the EntityManager (which serves as a first level cache). The valid values are "weak ... all its EntityManager instances. The level 2 cache is disabled by specifying 0 or 0mb. The <fetch> element <fetch
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JPA Metamodel API

by the EntityManager's getMetamodel method (both methods are equivalent). For example, given an EntityManager, em, a Metamodel instance can be obtained by: Metamodel metamodel = em.getMetamodel
6

JPA Query API

with an EntityManager (represented by em in the following code snippets), which serves as a factory
6

JPA Queries

getCriteriaBuilder method or by the EntityManager's getCriteriaBuilder method (both methods
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Step 3: Define an EJB Session Bean

.persistence.EntityManager; import javax.persistence.PersistenceContext; import javax.persistence.TypedQuery ... : @PersistenceContext private EntityManager em; // Stores a new guest: public void persist(Guest guest ... shown in the next step). Prepares an EntityManager automatically and injects it into the em field
1

Step 4: Add a Servlet Class

= (EntityManagerFactory)getServletContext().getAttribute("emf"); EntityManager em ... the application scope attribute, and then an EntityManager (representing a database connection
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Step 4: Add a Servlet Class

().getAttribute("emf"); EntityManager em = emf.createEntityManager(); try ... : The EntityManagerFactory is retrieved from the application scope attribute, and then an EntityManager

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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