Enterprise Java v120215Java Persistence: EntityManager1.

EnterpriseJava

v120215 Java Persistence: EntityManager 1

Java Persistence: EntityManager

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Goals

• Become familiar with the Java Persistence API and EntityManager

• Become familiar with how to setup a project using JPA and a provider (Hibernate)

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Objectives

• Provide an Overview of the Java Persistence API• Go through Details of the EntityManager• Go through some implementation details associated

with class projects

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Overview

• Earlier versions of EJB Specification defined the persistence layer– javax.ejb.EntityBean

• Java EE 5 moved persistence to its own specification– Java Persistence API (JPA) version 1.0– javax.persistence

• ease of use API above JDBC• Provides

– Object/Relational Mapping (ORM) Engine– Query Language (SQL-Like, based on former EJB-QL)

• Java EE 6 uses JPA 2.0

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javax.persistence.EntityManager

• Replaces much of the EJB 2.x “Home” functionality• Handles O/R Mapping of Entities to the database• Provides APIs

– inserting objects into database– getting objects from database– synchronizing objects with database– querying database

• Provides caching• Coordinates with transactional services (JTA)• Tightly integrated with Java EE and EJB, but not

limited to that environment

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Entities

• (formerly and sometimes still called Entity Beans)• are now Plain Old Java Objects (POJOs)

– nothing special happens when calling new

Author author = new Author();

• are not persistent until associated with an EntityManager

em.persist(author);

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Example Author POJO [email protected] class Author { private long id; private long version=0; private String firstName; private String lastName; private String subject; private Date publishDate; public Author() {} public Author(long id) { this.id = id; } @Id @GeneratedValue public long getId() { return id;} private void setId(long id) { this.id = id; } public String getFirstName() { return firstName; } public void setFirstName(String firstName) { this.firstName = firstName; } ... }

Warning: Using GeneratedValue without specifying a specific strategy should only be used when you have no intention of controlling how the provider manages primary keys for this object type. This would be rare.

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Creating Entity in DatabaseAuthor author = new Author(); //primary key will be genauthor.setFirstName("dr");author.setLastName("seuss");author.setSubject("children");author.setPublishDate(new Date());

log_.info("creating author:" + author);em.persist(author);log_.info("created author:" + author);

//output-creating author:id=0, fn=dr, ln=seuss, subject=children,

pdate=Fri Sep 15 11:54:15 EDT 2006-created author:id=50, fn=dr, ln=seuss, subject=children,

pdate=Fri Sep 15 11:54:15 EDT 2006

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Managed and Unmanaged Entities

• Unmanaged state (detached)– instance not associated with an EntityManager– state changes are not tracked– can be serialized to client and returned to be

synchronized with database– nothing equivalent to this state in EJB 2.1 entity beans

• Managed state (attached)– instance associated with an EntityManager– state changes are tracked within a Persistence Context– EJB 2.1 entity beans were always managed

• client interfaced with data through a proxy or state transferred through a Data Transfer Object

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Persistence Context

• A set of attached entity instances managed by an EntityManager

• All entities become detached once closed• Two types

– Transaction-scoped Persistence Contexts• begin/end at transaction boundaries• only made available through container managed

persistence contexts– Extended Persistence Contexts

• live beyond any single transaction• allow longer-lived interactions with database without

lengthy transactions tying up database resources

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Persistence Context Examples

• Transaction-scoped (inside server container)@PersistenceContext(unitName=”jpaDemo”)

EntityManager em;@TransactionAttribute(REQUIRED)public void update(long authorId, String type) {

Author author = em.find(Author.class, authorId);author.setType(type);

}

• Extended (inside or outside server container)EntityManager em = Persistence. createEntityManagerFactory(“jpaDemo”).createEntityManager();tx.begin(); //tx 1 beginsAuthor author = em.find(Author.class, authorId);tx.commit(); //tx 1 ends, but author remains managed...tx.begin(); //tx 2 beginsauthor.setType(type);tx.commit(); //tx 2 ends, and author is still managed until close

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Persistence Unit

• A set of classes that are mapped to the database• defined in META-INF/persistence.xml • must have an identity

– “” is a valid identity• Classes

– may be named in persistence.xml file– may be automatically scanned for in the classpath

• orm.xml– optionally provided to augment, provide, or replace class

persistence metadata– (more on orm.xml in Core ORM topic)

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Example Component Layout

META-INF/ +---persistence.xmlejava + ---examples +---… +---DAOException.class +---AuthorDAO.class +---jpa | +---JPAAuthorDAO.class

+--bo +---Author.class

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Example persistence.xml<?xml version="1.0" encoding="UTF-8"?><persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd" version="1.0">

<persistence-unit name="jpaDemo">

<jta-data-source>java:/ejavaDS</jta-data-source>

<properties> <property name="hibernate.hbm2ddl.auto" value="create"/> <property name="hibernate.show_sql" value="true"/ </properties> </persistence-unit> </persistence>

referenced by name

• global JNDI name by which provider references resource(will be used when deployed within server)• may use properties element in Java SE environments that lack JNDI

• vendor-specific way to configure persistence provider

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Another Example persistence.xml<?xml version="1.0" encoding="UTF-8"?><persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd" version="1.0">


<provider>org.hibernate.ejb.HibernatePersistence</provider>

<properties> <property name="hibernate.cache.provider_class" value="net.sf.ehcache.hibernate.Provider"/> <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/> <property name="hibernate.connection.url" value="jdbc:hsqldb:hsql://localhost:9001"/> <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/> <property name="hibernate.connection.password" value=""/> <property name="hibernate.connection.username" value="sa"/> <property name="hibernate.show_sql" value="false"/> <property name="hibernate.hbm2ddl.auto" value="create"/> </properties> </persistence-unit>

</persistence

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Solution-specific property option: hibernate.properties

• Easier to provide unit testing options that do not get propagated into production artifacts

$ cat hibernate.propertieshibernate.dialecte=org.hibernate.dialect.HSQLDialecthibernate.connection.url=jdbc:hsqldb:hsql://localhost:9001hibernate.connection.driver_class=org.hsqldb.jdbcDriverhibernate.connection.password=hibernate.connection.username=sahibernate.hbm2ddl.auto=create#hibernate.show_sql=true#hibernate.format_sql=true#hibernate.jdbc.batch_size=0

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persistence.xml elements

• name – identity to reference Persistence Unit• provider – fully qualified name of javax.persistence.PersistenceProvider

– not needed if provider found in classpath acceptable• mapping-file – resource path to optional mapping file

– can be used to specify <class>es or specify/override @Annotation details• jta-data-source

– vendor-specific reference to data source using JTA transactions• non-jta-data-source

– vendor-specific reference to data source using RESOURCE_LOCAL transactions• jar-file

– optional/additional jar file to scan for classes• class

– specifies entity classes not automatically scanned by provider• exclude-unlisted-classes

– if set, provider will not automatically scan archive for entity classes• properties

– may be used to provide vendor-specific properties to configure persistence providers

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Specifying an optional orm.xml file<?xml version="1.0" encoding="UTF-8"?><persistence xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd" version="1.0">


<provider>...</provider>

<mapping-file>META-INF/orm.xml</mapping-file>

<properties>

... </properties>

</persistence-unit>

</persistence

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Optional orm.xml overrides<?xml version="1.0" encoding="UTF-8"?><entity-mappings xmlns="http://java.sun.com/xml/ns/persistence/orm" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm http://java.sun.com/xml/ns/persistence/orm_1_0.xsd" version="1.0"> <entity class="ejava.examples.daoex.bo.Author" metadata-complete="false">

<table name="DAO_AUTHOR"/>

</entity></entity-mappings>

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Entities Discovered

• classes with @Entity annotation – in the persistence.xml's JAR file– contained in any JAR file listed in jar-file element

• classes mapped– with META-INF/orm.xml– with custom mapping files

• classes listed in persistence.xml's “<class>” element

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Java SE Steps

• Startup– Get EntityManagerFactory

• Runtime– Create EntityManager– Start Transaction– Interact with Entity Manager– Commit Transaction– Close EntityManager

• Shutdown– Close EntityManagerFactory

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javax.persistence.Persistence

• used to bootstrap persistence in Java SE environmentspublic class javax.persistence.Persistence { public static java.lang.String PERSISTENCE_PROVIDER; public javax.persistence.Persistence(); public static EntityManagerFactory createEntityManagerFactory(String puName); public static EntityManagerFactory createEntityManagerFactory(String puName, Map props);}

• example usageEntityManagerFactory emf = Persistence

.createEntityManagerFactory(“jpaDemo”);

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javax.persistence.EntityManagerFactory

• used to obtain reference to EntityManager in standard Java SE environmentspackage javax.persistence;public interface EntityManagerFactory{ EntityManager createEntityManager(); EntityManager createEntityManager(Map props); void close(); boolean isOpen();}

• Map used to supply or override properties in persistence.xml

• close() and isOpen() only valid for non-injected EMFs• example usage

– EntityManager em = emf.createEntityManager();

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javax.persistence.EntityManagerpackage javax.persistence;public interface EntityManager{ EntityTransaction getTransaction(); void persist(java.lang.Object); Object<T> find(Class<T>, Object pKey); Object<T> getReference(Class<T>, Object pKey); boolean contains(Object); Object merge(java.lang.Object); void refresh(java.lang.Object); void remove(java.lang.Object); Object find(java.lang.Class, java.lang.Object); void flush(); void clear(); void close(); isOpen();--- Query createQuery(java.lang.String); Query createNamedQuery(java.lang.String); Query createNativeQuery(java.lang.String); Query createNativeQuery(java.lang.String, java.lang.Class); Query createNativeQuery(java.lang.String, java.lang.String);

...

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persist()

Author author = new Author();author.setFirstName("dr");author.setLastName("seuss");author.setSubject("children");author.setPublishDate(new Date());em.persist(author);

• Extended persistence contexts– queues write until associated with transaction

• Transaction-scoped persistence contexts– illegal to call outside the scope of a transaction

• Actual write to the database depends on FlushMode– manually controlled with flush() call

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find()

Author author2=null;author2 = em.find(Author.class, id);log_.info("got author author:" + author2);

got author author:id=51, fn=thing, ln=one, subject=children, pdate=Fri Sep 15 11:54:15 EDT 2006

• Returns an instance of the class associated with the specified primary key value

– relationships are instantiated according to lazy-loading policies• Returns null if primary key not found• Uses generics, so no casting is necessary• Ids can be autoboxed without a manual wrapper• can be called outside the scope of a transaction• will be attached to open persistence context

– second find() will return same object

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getReference()

Author author2=null;author2 = em.getReference(Author.class, id);log_.info("got author author:" + author2);

• Similar to find()– Returns an instance of the class associated with the

specified primary key value• no guarantee that object state initialized

– Throws EntityNotFoundException if primary key not found

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createQuery()

• 5 createQuery() methodsQuery createQuery(String ejbqlString);Query createNamedQuery(String name);Query createNativeQuery(String sqlString);Query createNativeQuery(String sqlString, Class resultClass);Query createNativeQuery(String sqlString, String resultSetMap);

• example usageQuery query = em.createQuery("from jpaAuthor where id=" + id);Author author = (Author)query.getSingleResult();

• use EJB-QL and native (SQL) query languages• similar to find/getReference()–returned objects attached to open persistence context

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updating entities

• Updates to managed entities automatically get propagated to database according to flush policy public Author update(Author author) { Author dbAuthor = em.find(Author.class,author.getId()); dbAuthor.setFirstName(author.getFirstName()); dbAuthor.setLastName(author.getLastName()); dbAuthor.setSubject(author.getSubject()); dbAuthor.setPublishDate(author.getPublishDate()); return dbAuthor;}

– Note that if author passed in was already managed...• the changes have already been queued• the dbAuthor returned from the find() will be the same object as author• the sets are unnecessarily changing the values of the Author to their current

values

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merge()

• merges state changes to detached objects back into persistent storage

public Author updateByMerge(Author author) { Author managedAuthor = em.merge(author); return managedAuthor;}

• Original is left detached• Object returned is managed• Returned object is added to persistence if did not

already exist• Updates are made to existing object if already exists

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remove()

public void remove(Author author) { em.remove(author);}

– removes object from database• physically performed in database according to flush policy• cascades to related objects according to cascade policy

– object will be detached

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refresh() and contains()

• refresh()Author author = em.find(Author.class, id);em.refresh(author);

– used to make sure entity is in sync with database• cascades to related entities depending on cascade policy

– entity must be currently managed by entity manager instance

• contains()

if (em.contains(author)) { ...}

– used to test if instance is being managed by entity manager instance

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clear() and flush()

• clear()– detaches all entities– does not commit queued changes

• call flush() prior to clear()• flush()

– changes not synchronized with database until entity manager flushed• persist(), merge(), remove()

– occurs automatically before executing• correlated queries

– permits query to reflect changes in persistence context• transaction commit

– not impacted by primary key finders• find(), getReference()

– FlushMode• AUTO – default and most sane• COMMIT – an optimization to only flush and end of transaction. May

limit amount of database locking that occurs

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lock() and getDelegate()

• lock()– provides a pessimistic write lock for entity– will be covered with later during transaction topics

• getDelegate()– returns vendor object that implements EntityManager

interface– used to expose vendor-specific extension API

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EntityTransactions

• Only available for Entity Managers with an extended persistence context– Transaction-scoped persistence contexts are only

available with containers that support JTA transactions– Extended persistence contexts generally pertain to Java

SE applications using javax.persistence.Persistence class to get EntityManagerFactory

• transaction-like API for managing transactions within the single resource

• transaction context obtained from EntityManagerjavax.persistence.EntityTransaction tx = em.getTransaction();

tx.begin()tx.commit()tx.isActive()tx.rollback()

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Example private EntityManager em = ...

public void testQuery() throws Exception {

Author author = new Author(); author.setFirstName("test"); author.setLastName("Query"); author.setSubject("testing"); author.setPublishDate(new Date()); em.persist(author); //need to associate em with Tx to allow query to see entity in DB try { em.getTransaction().begin(); //note that the persist does not have to be within the tx em.getTransaction().commit(); } catch (Exception ex) { em.getTransaction().rollback(); fail("" + ex); }

Author author2 = null; Query query = em.createQuery( "from jpaAuthor where id=" + author.getId()); author2 = (Author)query.getSingleResult(); assertNotNull(author2); assertEquals(author.getFirstName(), author2.getFirstName()); assertEquals(author.getLastName(), author2.getLastName()); assertEquals(author.getSubject(), author2.getSubject()); assertEquals(author.getPublishDate(), author2.getPublishDate()); }

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Implementation/Testing Details

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Add JPA Dependencies• JPA API

– JPA 1.0<dependency> <groupId>javax.persistence</groupId> <artifactId>persistence-api</artifactId> <version>1.0</version> <scope>provided</scope></dependency>

– JPA 2.0<dependency> <groupId>org.hibernate.javax.persistence</groupId> <artifactId>hibernate-jpa-2.0-api</artifactId> <version>1.0.0.Final</version> <scope>provided</scope></dependency>

– Both available from the JBoss Maven/Nexus repository

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Add Provider Dependencies• Identify the JBoss repository <repositories> <repository> <id>jboss-nexus</id> <name>JBoss Nexus Repository</name> <url>https://repository.jboss.org/nexus/content/groups/public-jboss/</url> </repository> </repositories>

• Add hibernate-entitymanager– primary dependency we need to pull in hibernate– maven will pull in many other dependencies based on hibernate-

entitymanager's pom.xml <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-entitymanager</artifactId> <version>3.6.0.Final</version> <scope>test</scope> </dependency>

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Add Dependency Overrides• We have to pull in a library that will allow hibernate to use log4j

<dependency><groupId>org.slf4j</groupId><artifactId>slf4j-log4j12</artifactId><version>1.5.8</version><scope>test</scope>

</dependency>

• Otherwise, we’ll get the following error

Tests run: 12, Failures: 0, Errors: 12, Skipped: 0, Time elapsed: 0.078 sec <<< FAILURE!

testCreate(ejava.examples.dao.jpa.JPAAuthorDAODemo) Time elapsed: 0.031 sec <<< ERROR!

java.lang.NoClassDefFoundError: org/slf4j/impl/StaticLoggerBinder at org.slf4j.LoggerFactory.<clinit>(LoggerFactory.java:60)

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Add Standard DB Properties

• Identical to what was needed for JDBC <profile>  <id>hsql</id> <activation> <property>  <name>jdbcdb</name> <value>hsql</value> </property> </activation> <properties> <jdbc.driver>org.hsqldb.jdbcDriver</jdbc.driver> <jdbc.url>jdbc:hsqldb:hsql://localhost:9001</jdbc.url> <jdbc.user>sa</jdbc.user> <jdbc.password /> <hibernate.dialect>org.hibernate.dialect.HSQLDialect </hibernate.dialect> </properties> <dependencies> <dependency> <groupId>hsqldb</groupId> <artifactId>hsqldb</artifactId> <version>1.8.0.4</version> <scope>test</scope> </dependency> </dependencies> </profile>

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Design Mechanism to Pass DB Properties

• Compile-time property filtering– default values end up in .jar file; not ideal– much less work; good for prototypes– demonstrated here within JPA examples

• Runtime property passing– more realistic– more work

• could delegate details to a Test Utility Class– demonstrated in JDBC examples

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src/main/resources/META-INF/persistence.xml

<persistence ...> <persistence-unit name="jpaDemo"> <provider>org.hibernate.ejb.HibernatePersistence</provider> <properties> <property name="hibernate.dialect" value="${hibernate.dialect}"/> <property name="hibernate.connection.url" value="${jdbc.url}"/> <property name="hibernate.connection.driver_class" value="${jdbc.driver}"/> <property name="hibernate.connection.password" value="${jdbc.password}"/> <property name="hibernate.connection.username" value="${jdbc.user}"/> <property name="hibernate.show_sql" value="false"/> <property name="hibernate.format_sql" value="false"/> <!–- used in special cases <property name="hibernate.hbm2ddl.auto" value="create"/> <property name="hibernate.jdbc.batch_size" value=“0"/> --> </properties> </persistence-unit></persistence>

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src/test/resources/hibernate.properties

hibernate.dialecte=${hibernate.dialect}hibernate.connection.url=${jdbc.url}hibernate.connection.driver_class=${jdbc.driver}hibernate.connection.password=${jdbc.password}hibernate.connection.username=${jdbc.user}#only use auto create for quick prototypes#hibernate.hbm2ddl.auto=createhibernate.show_sql=truehibernate.format_sql=true# eliminate batching to help debug DB errors#hibernate.jdbc.batch_size=0

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Add Resource Filtering Spec to pom.xml

• This overrides the default behavior of resource handling

<build>  <!–- if $vars in src/main/resources branch --> <resources> <resource> <directory>src/main/resources</directory> <filtering>true</filtering> </resource> </resources> <!-- if $vars in src/test/resources branch <testResources> <testResource> <directory>src/test/resources</directory> <filtering>true</filtering> </testResource> </testResources>

... </build>

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target/classes/META-INF/persistence.xml

<persistence ...> <persistence-unit name="jpaDemo"> <provider>org.hibernate.ejb.HibernatePersistence</provider> <properties> <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/> <property name="hibernate.connection.url" value="jdbc:hsqldb:hsql://localhost:9001"/> <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/> <property name="hibernate.connection.password" value=""/> <property name="hibernate.connection.username" value="sa"/> <property name="hibernate.show_sql" value="false"/> <property name="hibernate.hbm2ddl.auto" value="create"/> </properties> </persistence-unit></persistence>

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target/test-classes/hibernate.properties

hibernate.dialecte=org.hibernate.dialect.HSQLDialecthibernate.connection.url=jdbc:hsqldb:hsql://localhost:9001hibernate.connection.driver_class=org.hsqldb.jdbcDriverhibernate.connection.password=hibernate.connection.username=sahibernate.hbm2ddl.auto=createhibernate.show_sql=false#hibernate.format_sql=true#hibernate.jdbc.batch_size=0

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Setup JUnit TestCase

import static org.junit.Assert.*;import org.junit.*;

public class JPAAccountDAOTest {

@BeforeClasspublic static void setUpClass() throws Exception { … }

@Beforepublic void setUp() throws Exception { … }

@Afterpublic void tearDown() throws Exception { … }

@AfterClasspublic static void tearDownClass() throws Exception { … }

@Testpublic void testJPACreate() throws Exception { … }

@Testpublic void testXXX() throws Exception { … }

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Setup EntityManager within TestCasepublic class JPAAccountDAOTest {

private static Log log = LogFactory.getLog(JPAAccountDAO.class);

private EntityManagerFactory emf;private EntityManager em;private AccountDAO dao;

@Beforepublic void setUp() throws Exception { emf = Persistence.createEntityManagerFactory("eSalesBO"); em = emf.createEntityManager();

dao = new JPAAccountDAO(); ((JPAAccountDAO)dao).setEntityManager(em);

cleanup(); //get env to a known state before starting tests //may want in its own transaction

em.getTransaction().begin(); //optional //have transaction started prior to test

}

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Teardown EntityManager within TestCase

@Afterpublic void tearDown() throws Exception {

if (em != null) {EntityTransaction tx = em.getTransaction();if (tx.isActive()) {

if (tx.getRollbackOnly()) { tx.rollback(); }else { tx.commit(); }

}em.close();

}if (emf != null) {

emf.close();}

}

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(optional!)Potential Utiltity Classpackage ejava.examples.dao.jpa;

import java.util.HashMap;import java.util.Map;import javax.persistence.EntityManagerFactory;import javax.persistence.Persistence;

public class JPAUtil { private static final Map<String, EntityManagerFactory> factories = new HashMap<String, EntityManagerFactory>(); public static EntityManagerFactory getEntityManagerFactory(String puName) { EntityManagerFactory emf = factories.get(puName); if (emf == null) { synchronized(factories) { emf = factories.get(puName); if (emf == null) { emf = Persistence.createEntityManagerFactory(puName); factories.put(puName, emf); } } } return emf; } public static void close() { synchronized(factories) { for(String puName : factories.keySet()) { factories.get(puName).close(); } factories.clear(); } }}

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(optional!) Junit Test Suites

• Supports the one-time startup or shutdown of components

public class AllTest extends TestCase { private static Log log_ = LogFactory.getLog(AllTest.class); public static Test suite() { TestSuite tests = new TestSuite(); tests.addTestSuite(JPAAuthorDAODemo.class); tests.addTestSuite(JPANoDAODemo.class); TestSetup wrapper = new TestSetup(tests) { //one-time setup public void setUp() throws Exception { }

//one-time tear down public void tearDown() throws Exception { JPAUtil.close(); } }; return wrapper; }

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JUnit Tests@Testpublic void testJPACreate() throws Exception {

log.info("*** testJPACreate ***");… Account account = new Account(userId); account.setFirstName(firstName); account.getAddresses().add(new Address(0, "Shipping", "Laurel")); account.getAddresses().add(new Address(0, "Billing", "Columbia")); log.debug("instantiated Account:" + account); dao.createAccount(account); log.debug("dao created Account:" + account); … Account account2 = em.find(Account.class, userId); assertNotNull(account2); assertEquals("unexpected first name", firstName, account2.getFirstName()); assertEquals("unexpected number of addresses", account.getAddresses().size(), account2.getAddresses().size());

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Summary

• Java Persistence API– Java standard for mapping objects to relational databases– currently part of Java EE; will be in Java SE 6– eliminates the need or desire for EJB 2.1 entity

• Entity– a POJO – operates both detached and managed by OR Mapping

• Persistence Unit– a set of entity classes mapped to the database schema

• Persistence Context– a set of objects that managed– Transaction-scoped or Extended

• javax.persistence.EntityManager– manages objects in a persistence context

• javax.persistence.EntityManagerFactory– used to create individual entity managers

• javax.persistence.Persistence– used to bootstrap EntityManagerFactory into Java SE applications

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References

• “Enterprise JavaBeans 3.0, 5th Edition”; Burke & Monsen-Haefel; ISBN 0-596-00978-X; O'Reilly

Enterprise Java v120215Java Persistence: EntityManager1.

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