Java Persistence API

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1 Java Persistence API Entities and EntityManager Revision: v Built on: :40 EST Copyright 2015 jim stafford This presentation provides and introduction to JPA and coverage of the methods of the EntityManager.

3 Purpose... v 1. Goals... v 2. Objectives... v 1. JPA Overview Background EntityManager Entity JPA Example Entity States Managed Detached Persistence Context Persistence Unit Example Layout Persistence.xml Application Example Server Example Optional hibernate.properties Sample orm.xml persistence.xml Elements Entity Discovery Basic Steps Entity Manager Methods Basic CRUD Operations Membership Operations State Synchronization Operations Locking Operations Query Operations Other Operations Entity Manager CRUD Methods persist() find() getreference() merge() remove() Entity Manager Membership Methods contains() clear() detach() Entity Manager State Synchronization Methods flush() FlushMode refresh() Entity Manager Locking Methods iii

4 Java Persistence API 5.1. Primary Lock Types LockModeType lock() find(lock) refresh(lock) getlockmode() Entity Manager Query Methods JPA Queries Native Queries Criteria Queries Other Entity Manager Methods isopen() close() gettransaction() jointransaction() unwrap() getdelegate() getmetamodel() getentitymanagerfactory() setproperties()/getproperties() JPA Maven Environment JPA Maven Dependencies JPA API classes JPA Provider classes Database Supplying Runtime Properties Turn on Resource Filtering in pom.xml Use ${variable References in Resource Files Define Property Values in Parent pom.xml Run with Filtered Values iv

5 Purpose 1. Goals Introduce the Java Persistence API and its capabilities 2. Objectives At the completion of this topic, the student shall have an understanding of: Requirements for entity classes How to define a persistence unit How to obtain an entity manager Persistence methods available from EntityManager be able to: Define a Java class as an entity Define a persistence unit with entity class(es) Implement DAO operations in terms of javax.persistence.persistence API v

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7 Chapter 1. JPA Overview 1.1. Background Earlier versions of EJB Spec defined persistence as part of javax.ejb.entitybean JavaEE 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 (JPA-QL) - SQL-like - main carryover from EJB 2.x JavaEE 6 advanced specification Java Persistence API (JPA) version 2.0 More mapping capabilities More entity manager capabilities Standardization of properties Criteria API JavaEE 7 enhanced specification Java Persistence API (JPA) version 2.1 Converters - to convert attributes to/from DB types Criteria API Bulk Updates Stored Procedure Query support Partial fetching of objects EntityManager Replaced EJB 2.x Home Functionality Handles O/R Mapping to the database Provides APIs for Inserting into database Updating entities in database Finding and querying for entities in database Removing entities from database Provides caching Integrates with JTA transactions Tightly integrated with JavaEE and EJB, but not coupled to it 1.3. Entity Plain Old Java Objects (POJOs) Nothing special happens when calling new() Author author = new Author(); 1

8 Chapter 1. JPA Overview From JPA perspective the above is a new/unmanaged entity Persistent when associated with an entity manager/persistence context public class private long id; private long version=0; private String firstname; private String lastname; private String subject; private Date publishdate; public Author() {... Entity minimum requirements: Annotated as entity or declared in orm.xml Unique identity (form primary key(s)) Non-private default constructor 1.4. JPA Example Author author = new Author(); author.setfirstname("dr"); author.setlastname("seuss"); author.setsubject("children"); author.setpublishdate(new Date()); log.debug("creating author:" + author); assertfalse("unexpected initialized id", author.getid() > 0); log.debug("em.contains(author)=" + em.contains(author)); em.persist(author); log.debug("created author:" + author); asserttrue("missing id", author.getid() > 0); log.debug("em.contains(author)=" + em.contains(author)); -creating author:ejava.examples.daoex.bo.author@1d8e9e, id=0, fn=dr, ln=seuss, subject=children, pdate=mon Sep 17 00:22:25 EDT 2012, version=0 -em.contains(author)=false -created author:ejava.examples.daoex.bo.author@1d8e9e, id=50, fn=dr, ln=seuss, subject=children, pdate=mon Sep 17 00:22:25 EDT 2012, version=0 2

9 Entity States -em.contains(author)=true 1.5. Entity States Managed Associated with persistence context Has identity Changes to the entity will impact the database Method em.contains(entity) returns true Detached Has identity but not associated with persistence context Changes to entity will not impact the database Method em.contains(entity) returns false An entity becomes detached when: Has not yet been persisted After a transaction-scoped transaction is committed After a transaction rollback Manually detaching entity from persistence context thru em.detach() Manually clearing the persistence context thru em.clear() Closing EntityManager Serializing entity thru a remote interface 1.6. Persistence Context A set of managed instances managed by an EntityManager All entities become detached once closed Two types: Extended Author author = new Author();... em.persist(author); em.gettransaction().begin(); em.gettransaction().commit(); author.setfirstname("foo"); em.gettransaction().begin(); em.gettransaction().commit(); em.gettransaction().begin(); author.setfirstname("bar"); em.gettransaction().commit(); Live beyond a single transaction Allow long-lived algorithms to process without tying up a database transaction 3

10 Chapter 1. JPA Overview public Author createauthor(...) { Author author = new Author();... em.persist(author); return author; Begin/end at transaction boundaries Injected by containers 1.7. Persistence Unit A set of classes that are mapped to the database Defined in META-INF/persistence.xml Entity classes may be named in persistence.xml or searched for Entity mapping may be provided, augmented, or overridden with orm.xml mapping file 1.8. Example Layout -- ejava `-- examples `-- daoex -- AuthorDAO.class -- bo `-- Author.class -- DAOException.class `-- jpa `-- JPAAuthorDAO.class `-- META-INF -- orm.xml `-- persistence.xml 1.9. Persistence.xml Application Example <?xml version="1.0" encoding="utf-8"?> <persistence xmlns=" xmlns:xsi=" xsi:schemalocation= " version="2.0"> <persistence-unit name="jpademo"> 4

11 Server Example <provider>org.hibernate.ejb.hibernatepersistence</provider> <mapping-file>meta-inf/orm.xml</mapping-file> <properties>  <property name="javax.persistence.jdbc.url" value="jdbc:h2:./target/h2db/ejava"/> <property name="javax.persistence.jdbc.driver" value="org.h2.driver"/> <property name="javax.persistence.jdbc.user" value="sa"/> <property name="javax.persistence.jdbc.password" value=""/>  <property name="hibernate.dialect" value="org.hibernate.dialect.h2dialect"/> <property name="hibernate.hbm2ddl.auto" value="create"/> <property name="hibernate.show_sql" value="true"/> <property name="hibernate.format_sql" value="true"/>  </properties> </persistence-unit> </persistence> Above example defines properties for entity manager to establish physical connections to database Server Example <?xml version="1.0" encoding="utf-8"?> <persistence xmlns=" xmlns:xsi=" xsi:schemalocation= " version="2.0"> <persistence-unit name="ejbsessionbank"> <provider>org.hibernate.ejb.hibernatepersistence</provider> <jta-data-source>java:jboss/datasources/exampleds</jta-data-source> <jar-file>lib/ejbsessionbankimpl snapshot.jar</jar-file> <properties> <property name="hibernate.dialect" value="org.hibernate.dialect.h2dialect"/> <property name="hibernate.show_sql" value="false"/>  <property name="hibernate.hbm2ddl.auto" value="create"/>  </properties> </persistence-unit> </persistence> Above example used DataSource from JNDI tree to obtain connections to database 5

12 Chapter 1. JPA Overview Optional hibernate.properties Can be used to specify connection properties outside of persistence.xml Useful in separating production mapping information from runtime connection properties #hibernate-specific alternate source of persistence.xml properties hibernate.dialect=org.hibernate.dialect.h2dialect hibernate.connection.url=jdbc:h2:./target/h2db/ejava hibernate.connection.driver_class=org.h2.driver hibernate.connection.password= hibernate.connection.username=sa hibernate.hbm2ddl.auto=create hibernate.show_sql=true hibernate.format_sql=true #hibernate.jdbc.batch_size= Sample orm.xml <?xml version="1.0" encoding="utf-8"?> <entity-mappings xmlns=" xmlns:xsi=" xsi:schemalocation= " version="2.0"> <entity class="ejava.examples.daoex.bo.author" access="field" metadata-complete="false" name="jpaauthor"> <table name="dao_author"/> <attributes> <id name="id"> <generated-value strategy="sequence" generator="author_sequence"/> </id> </attributes> </entity> </entity-mappings> Note The JPA 2.1 schema references are shown below. They have been left out of all class examples because they are not yet compatible with the schema generation plugin (hibernate3) used in class. It is unlikely that you will need features unique to JPA 2.1 declared in your XML files but know if you include references to JPA 2.1 you must use an alternate means of generating schema -- possibly manually. 6

13 persistence.xml Elements <?xml version="1.0" encoding="utf-8"?> <persistence xmlns=" xmlns:xsi=" xsi:schemalocation=" persistence/persistence_2_1.xsd" version="2.1"> <?xml version="1.0" encoding="utf-8"?> <entity-mappings xmlns=" xmlns:xsi=" xsi:schemalocation=" persistence/orm_2_1.xsd" version="2.1"> persistence.xml Elements name Identity used to reference persistence unit provider Fully qualified name of javax.persistence.persistenceprovider Not needed if provider is in classpath mapping-file Path reference to an orm.xml mapping file jta-data-source JNDI path of a JTA javax.sql.datasource non-jta-datasource JNDI path of a RESOURCE_LOCAL javax.sql.datasource jarfile Reference to an archive with entity classes class Fully qualified package name of entity class One source of entity information exclude-unlisted-classes If set, provider will not scan to discover entity classes properties name/value property pairs to express additional configuration info Entity Discovery Classes annotation In persistence.xml's JAR file Contained in any JAR listed in persistence.xml#jar-file element Classes mapped 7

14 Chapter 1. JPA Overview With a META-INF/orm.xml file With custom mapping files Classes listed in persistence.xml#class element Basic Steps setup Create EntityManagerFactory public class javax.persistence.persistence extends java.lang.object{ public static javax.persistence.entitymanagerfactory createentitymanagerfactory(java.lang.string); public static javax.persistence.entitymanagerfactory createentitymanagerfactory(java.lang.string, java.util.map);... private static EntityManagerFactory public static void setupclass() { emf = Persistence.createEntityManagerFactory("jpaDemo"); Create EntityManager public interface javax.persistence.entitymanagerfactory{ public abstract javax.persistence.entitymanager createentitymanager(); public abstract javax.persistence.entitymanager createentitymanager(java.util.map);... private EntityManager public void setup() throws Exception { em = emf.createentitymanager(); Runtime Start Transaction em.gettransaction().begin(); Interact with EntityManager em.persist(author); Commit Transaction em.gettransaction().commit(); 8

15 Entity Manager Methods teardown Close public void teardown() throws Exception { try { if (em!= null) { if (!em.gettransaction().isactive()) { em.gettransaction().begin(); em.gettransaction().commit(); else if (!em.gettransaction().getrollbackonly()) { em.gettransaction().commit(); else { em.gettransaction().rollback(); finally { if (em!= null) { em.close(); em=null; Close public static void teardownclass() { if (emf!= null) { emf.close(); emf=null; Entity Manager Methods public interface javax.persistence.entitymanager{ Basic CRUD Operations void persist(object entity); <T> T find(class<t> entityclass, Object primarykey); <T> T find(class<t> entityclass, Object primarykey, Map<String, Object> properties); <T> T merge(t entity); void remove(object entity); <T> T getreference(class<t> entityclass, Object primarykey); 9

16 Chapter 1. JPA Overview Membership Operations void clear(); void detach(object entity); boolean contains(object entity); State Synchronization Operations void flush(); void setflushmode(javax.persistence.flushmodetype); javax.persistence.flushmodetype getflushmode(); void refresh(object); void refresh(object, java.util.map); Locking Operations void lock(object entity, javax.persistence.lockmodetype); void lock(object entity, javax.persistence.lockmodetype, Map<String, Object> properties); <T> T find(class<t> entityclass, Object primarykey, javax.persistence.lockmodetype); <T> T find(class<t> entityclass, Object primarykey, javax.persistence.lockmodetype, Map<String, Object> properties); void refresh(object, javax.persistence.lockmodetype); void refresh(object, javax.persistence.lockmodetype, Map<String, Object> properties); javax.persistence.lockmodetype getlockmode(object entity); Query Operations javax.persistence.query createquery(string jpaql); <T> javax.persistence.typedquery<t> createquery(string jpaql, Class<T> resultclass); javax.persistence.query createnamedquery(string name); <T> javax.persistence.typedquery<t> createnamedquery(string name, Class<T> resultclass); javax.persistence.query createnativequery(string sql); javax.persistence.query createnativequery(string sql, Class resultclass); javax.persistence.query createnativequery(string sql, String resultmapping); <T> javax.persistence.typedquery<t> createquery(javax.persistence.criteria.criteriaquery<t> criteria); javax.persistence.criteria.criteriabuilder getcriteriabuilder(); Other Operations 10

17 Other Operations void close(); boolean isopen(); javax.persistence.entitytransaction gettransaction(); void jointransaction(); void setproperty(string key, Object value); java.util.map getproperties(); <T> T unwrap(class<t> clazz); Object getdelegate(); javax.persistence.metamodel.metamodel getmetamodel(); javax.persistence.entitymanagerfactory getentitymanagerfactory(); 11

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19 Chapter 2. Entity Manager CRUD Methods 2.1. persist() Author author = new Author(); author.setfirstname("dr"); author.setlastname("seuss"); author.setsubject("children"); author.setpublishdate(new Date()); log.debug("creating author:" + author); em.persist(author); log.debug("created author:" + author); -creating author:ejava.examples.daoex.bo.author@17e7691, id=0, fn=dr, ln=seuss, subject=children, pdate=sun Sep 16 10:14:32 EDT 2012, version=0 -created author:ejava.examples.daoex.bo.author@17e7691, id=50, fn=dr, ln=seuss, subject=children, pdate=sun Sep 16 10:14:32 EDT 2012, version=0 Inserts entity into database Actual insert time depends on transaction active and FlushMode Extended Persistence Context - queues insert until transaction active Transaction-Scoped Persistence Context - always has transaction active Flush occurs automatically prior to or during commit() Flush can be forced with manual em.flush() call New or removed entity enters managed state All further changes are watched and will update database log.debug("em.contains(author)=" + em.contains(author)); em.persist(author); log.debug("created author:" + author); log.debug("em.contains(author)=" + em.contains(author)); -em.contains(author)=false -created author:... -em.contains(author)=true Existing entity is ignored Cascades will still occur for CascadeType.PERSIST and ALL relationships em.persist(author);... em.persist(author); Detached entities will be rejected 13

20 Chapter 2. Entity Manager CRU... Entities with an identity but not associated with a persistence context... Author author = new Author(1); author.setfirstname("dr"); log.debug("creating author:" + author); log.debug("em.contains(author)=" + em.contains(author)); try { em.persist(author); fail("did not detect detached entity"); catch (PersistenceException ex) { log.debug("caught expected exception:" + ex.getlocalizedmessage(), ex); log.debug("em.contains(author)=" + em.contains(author)); -creating author:ejava.examples.daoex.bo.author@ad339b, id=1,... -em.contains(author)=false -caught expected exception:javax.persistence.persistenceexception: org.hibernate.persistentobjectexception: detached entity passed to persist: ejava.examples.daoex.bo.author -em.contains(author)=false 2.2. find() <T> T find(class<t> entityclass, Object primarykey); <T> T find(class<t> entityclass, Object primarykey, Map<String, Object> properties); Searches for the entity by primary key value Returns managed entity if found, else null Properties permitted for vendor-specific values and ignored if not understood 2.3. getreference() <T> T getreference(class<t> entityclass, Object primarykey); Searches for the entity by primary key Returns a LAZY load reference if found Throws EntityNotFoundException if not exist 2.4. merge() //create initial author Author author = new Author();... 14

21 remove() em.persist(author); //create detached author with changes Author author2 = new Author(author.getId()); author2.setfirstname("updated " + author.getfirstname());... //merge changes Author tmp = em.merge(author2); em.gettransaction().begin(); em.gettransaction().commit();... //verify results assertfalse("author2 is managed", em.contains(author2)); asserttrue("tmp Author is not managed", em.contains(tmp)); assertsame("merged result not existing managed", author, tmp);... //verify changes were made to the DB Author author3 = em.find(author.class, author.getid()); assertequals("updated " + firstname, author3.getfirstname()); Update database with state of detached object State of detached object copied into managed entity or new instance created Merging a managed entity is ignored. CascadeType.MERGE and ALL relationships are propagated Merging a removed entity instance results in an IllegalArgumentException Includes automatic checking property Could be replaced with manual merge 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 The above manual merge will successfully merge a transient entity -- but what errors and conditions does it not account for? 2.5. remove() void remove(object entity); Managed entity is removed from database 15

22 Chapter 2. Entity Manager CRU... Actual delete time depends on transaction active and FlushMode Extended Persistence Context - queues delete until transaction active New entities are ignored but CascadeType.REMOVE and ALL relationships are cascaded log.debug("em.contains(author)=" + em.contains(author)); em.remove(author); log.debug("em.contains(author)=" + em.contains(author)); -em.contains(author)=false -HHH000114: Handling transient entity in delete processing -em.contains(author)=false Detached entities are rejected Author author = new Author(1);... try { em.remove(author); fail("did not reject removal of detached object"); catch (IllegalArgumentException ex) { log.debug("caught expected exception:" + ex); -caught expected exception:java.lang.illegalargumentexception: Removing a detached instance ejava.examples.daoex.bo.author#1 Removed entities are ignored Author author = new Author();... log.debug("peristed:" + author); log.debug("em.contains(author)=" + em.contains(author)); em.remove(author); log.debug("em.contains(author)=" + em.contains(author)); //entity managers will ignore the removal of a removed entity em.remove(author); log.debug("em.contains(author)=" + em.contains(author)); -peristed:ejava.examples.daoex.bo.author@6c5356, id=50,... -em.contains(author)=true -em.contains(author)=false -em.contains(author)=false 16

23 Chapter 3. Entity Manager Membership Methods 3.1. contains() boolean contains(object entity); Returns true if object is managed in the persistence context 3.2. clear() void clear(); Clears all entities and queued changes from the persistence context All entities become detached 3.3. detach() em.persist(author); //callers can detach entity from persistence context log.debug("em.contains(author)="+em.contains(author)); log.debug("detaching author"); em.gettransaction().begin(); em.flush(); em.detach(author); log.debug("em.contains(author)="+em.contains(author)); em.gettransaction().commit(); //changes to detached entities do not change database author.setfirstname("foo"); em.gettransaction().begin(); em.gettransaction().commit(); Author author2 = em.find(author.class, author.getid()); log.debug("author.firstname=" + author.getfirstname()); log.debug("author2.firstname=" + author2.getfirstname()); assertfalse("unexpected name change", author.getfirstname().equals(author2.getfirstname())); -em.contains(author)=true -detaching author -em.contains(author)=false -author.firstname=foo 17

24 Chapter 3. Entity Manager Mem... -author2.firstname=dr Detaches existing entity from persistence context Detach cascaded to CascadeType.DETACH and ALL relationships Subsequent changes to entity will not change database Portable use requires call to flush() prior to detach() New entities are ignored Author author = new Author(); log.debug("em.contains(author)="+em.contains(author)); log.debug("detaching author"); em.detach(author); log.debug("em.contains(author)="+em.contains(author)); -em.contains(author)=false -detaching author -em.contains(author)=false Detached entities are ignored Author author = new Author();... em.persist(author); em.gettransaction().begin(); em.gettransaction().commit(); //detaching detached entity will be ignored Author detached = new Author(author.getId()); log.debug("em.contains(author)="+em.contains(detached)); log.debug("detaching detached author"); em.detach(detached); log.debug("em.contains(author)="+em.contains(detached)); -em.contains(author)=false -detaching detached author -em.contains(author)=false 18

25 Chapter 4. Entity Manager State Synchronization Methods 4.1. flush() void flush(); Synchronizes cached changes with underlying database Requires active transaction 4.2. FlushMode void setflushmode(javax.persistence.flushmodetype); javax.persistence.flushmodetype getflushmode(); AUTO (default) - unspecified COMMIT - flush only happens during commit 4.3. refresh() em.persist(author); em.gettransaction().begin(); em.gettransaction().commit(); //change DB state out-of-band from the cache em.gettransaction().begin(); String newname="foo"; int count=em.createquery( "update jpaauthor a set a.firstname=:name where a.id=:id").setparameter("id", author.getid()).setparameter("name", newname).executeupdate(); em.gettransaction().commit(); assertequals("unexpected count", 1, count); //object state becomes stale when DB changed out-of-band log.debug("author.firstname=" + author.getfirstname()); assertfalse("unexpected name", author.getfirstname().equals(newname)); //get the cached object back in sync log.debug("calling refresh"); em.refresh(author); 19

26 Chapter 4. Entity Manager Sta... log.debug("author.firstname=" + author.getfirstname()); assertequals("unexpected name", newname, author.getfirstname()); -author.firstname=dr -calling refresh -author.firstname=foo Updates/overwrites cached entity state with database state Refresh of new entity results in java.lang.illegalargumentexception Author author = new Author(); author.setfirstname("test"); author.setlastname("new"); try { em.refresh(author); fail("refresh of new entity not detected"); catch (IllegalArgumentException ex) { log.debug("caught expected exception:" + ex); -caught expected exception:java.lang.illegalargumentexception: Entity not managed Refresh of detached entity results in java.lang.illegalargumentexception em.persist(author); em.gettransaction().begin(); em.gettransaction().commit(); //refreshing a detached entity will get rejected Author detached = new Author(author.getId()); em.refresh(author); log.debug("refreshed managed entity"); try { em.refresh(detached); fail("refresh of detached entity not detected"); catch (IllegalArgumentException ex) { log.debug("caught expected exception:" + ex); -refreshed managed entity -caught expected exception:java.lang.illegalargumentexception: Entity not managed 20

27 Chapter 5. Entity Manager Locking Methods 5.1. Primary Lock Types Optimistic Entity assumed not to have concurrent access No active database locks are obtained at start Success judged based on entity state at end State tracked in field Pessimistic Entity requires mitigation for concurrent access Active database locks are obtained at start of transaction 5.2. LockModeType NONE No locks OPTIMISTIC (was READ) Requires entity to have property Prevent dirty reads Prevent non-repeatable reads OPTIMISTIC_FORCE_INCREMENT (was WRITE) Requires entity to have property Update only occurs if change has proper version Version is incremented upon update Incorrect version results in OptimisticLockException PESSIMISTIC_READ Supported with or property Obtains active database lock Provides repeatable reads Does not block other reads PESSIMISTIC_WRITE Supported with or property Forces serialization of entity updates among transactions PESSIMISTIC_FORCE_INCREMENT Requires entity to have property PESSIMISTIC_WRITE lock with increment 5.3. lock() void lock(object entity, javax.persistence.lockmodetype); void lock(object entity, javax.persistence.lockmodetype, Map<String, Object> properties); 21

28 Chapter 5. Entity Manager Loc... Requests lock on entity 5.4. find(lock) <T> T find(class<t> entityclass, Object primarykey, javax.persistence.lockmodetype); <T> T find(class<t> entityclass, Object primarykey, javax.persistence.lockmodetype, Map<String, Object> properties); Find object by primary key and lock 5.5. refresh(lock) void refresh(object, javax.persistence.lockmodetype); void refresh(object, javax.persistence.lockmodetype, Map<String, Object> properties); Refresh entity state and obtain lock 5.6. getlockmode() javax.persistence.lockmodetype getlockmode(object entity); Get lock mode for entity 22

29 Chapter 6. Entity Manager Query Methods 6.1. JPA Queries javax.persistence.query createquery(string jpaql); <T> javax.persistence.typedquery<t> createquery(string jpaql, Class<T> resultclass); javax.persistence.query createnamedquery(string name); <T> javax.persistence.typedquery<t> createnamedquery(string name, Class<T> resultclass); Create query based on JPA Query Language (JPAQL) 6.2. Native Queries javax.persistence.query createnativequery(string sql); javax.persistence.query createnativequery(string sql, Class resultclass); javax.persistence.query createnativequery(string sql, String resultmapping); Create query based on SQL 6.3. Criteria Queries <T> javax.persistence.typedquery<t> createquery(javax.persistence.criteria.criteriaquery<t> criteria); javax.persistence.criteria.criteriabuilder getcriteriabuilder(); Create query based on typed criteria API 23

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31 Chapter 7. Other Entity Manager Methods 7.1. isopen() boolean isopen(); Returns true if persistence context is open 7.2. close() void close(); Closes persistence context All contained entities become detached 7.3. gettransaction() javax.persistence.entitytransaction gettransaction(); Returns transaction object for inspection and control Invalid call for transaction-scoped persistence contexts 7.4. jointransaction() void jointransaction(); Associate a persistence context with a JTA transaction 7.5. unwrap() <T> T unwrap(class<t> clazz); Return object of specified type Provides access to underlying implementation classes 25

32 Chapter 7. Other Entity Manag getdelegate() Object getdelegate(); Returns vendor-specific object backing EntityManager 7.7. getmetamodel() javax.persistence.metamodel.metamodel getmetamodel(); Returns metamodel object for persistence context 7.8. getentitymanagerfactory() javax.persistence.entitymanagerfactory getentitymanagerfactory(); Returns EntityManagerFactory associated with EntityManager 7.9. setproperties()/getproperties() void setproperty(string key, Object value); java.util.map getproperties(); Access EntityManager properties 26

33 Chapter 8. JPA Maven Environment src -- main -- java `-- ejava `-- examples `-- daoex -- AuthorDAO.java -- bo `-- Author.java -- DAOException.java `-- jpa `-- JPAAuthorDAO.java `-- resources `-- META-INF -- orm.xml `-- persistence.xml (could be placed in src/test branch) `-- test -- java `-- ejava `-- examples `-- daoex `-- jpa -- JPAAuthorDAOTest.java -- JPACRUDTest.java `-- JPATestBase.java `-- resources -- hibernate.properties (optional) `-- log4j.xml 8.1. JPA Maven Dependencies JPA API classes <dependency> <groupid>org.hibernate.javax.persistence</groupid> <artifactid>hibernate-jpa-2.1-api</artifactid> <version>1.0.0.final</version> <scope>provided</scope> </dependency> JPA Provider classes <dependency> <groupid>org.hibernate</groupid> <artifactid>hibernate-entitymanager</artifactid> 27

34 Chapter 8. JPA Maven Environment <version>4.3.4.final</version> <scope>test</scope> </dependency> <dependency> <groupid>org.slf4j</groupid> <artifactid>slf4j-log4j12</artifactid> <version>1.6.1</version> <scope>test</scope> </dependency> Database <dependency> <groupid>com.h2database</groupid> <artifactid>h2</artifactid> <scope>test</scope> </dependency> 8.2. Supplying Runtime Properties Turn on Resource Filtering in pom.xml <build> <resources> <resource> <directory>src/main/resources</directory> <filtering>true</filtering> </resource> </resources> <testresources> <testresource> <directory>src/test/resources</directory> <filtering>true</filtering> </testresource> </testresources>... </build> Above will depend on whether you use src/main or src/test for resource file(s) Use ${variable References in Resource Files <properties>  <property name="javax.persistence.jdbc.url" value="${jdbc.url"/> <property name="javax.persistence.jdbc.driver" value="${jdbc.driver"/> <property name="javax.persistence.jdbc.user" value="${jdbc.user"/> <property name="javax.persistence.jdbc.password" value="${jdbc.password"/> 28

35 Define Property Values in Parent pom.xml  <property name="hibernate.dialect" value="${hibernate.dialect"/>... </properties> Define Property Values in Parent pom.xml <properties> <jdbc.driver>org.h2.driver</jdbc.driver> <jdbc.url>jdbc:h2:${basedir/target/h2db/ejava</jdbc.url> <jdbc.user>sa</jdbc.user> <jdbc.password/> <hibernate.dialect> org.hibernate.dialect.h2dialect </hibernate.dialect> </properties> Run with Filtered Values <properties>  <property name="javax.persistence.jdbc.url" value="jdbc:h2:/home/jcstaff/proj/ejava-javaee/git/jpadao/target/h2db/ ejava"/> <property name="javax.persistence.jdbc.driver" value="org.h2.driver"/> <property name="javax.persistence.jdbc.user" value="sa"/> <property name="javax.persistence.jdbc.password" value=""/>  <property name="hibernate.dialect" value="org.hibernate.dialect.h2dialect"/>... </properties> 29

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Database Connection using JPA. Working with the Java Persistence API (JPA) consists of using the following interfaces:

Database Connection using JPA. Working with the Java Persistence API (JPA) consists of using the following interfaces: JPA - drugi deo Database Connection using JPA Working with the Java Persistence API (JPA) consists of using the following interfaces: Database Connection using JPA Overview A connection to a database is