1. JPA2 BRIEF INTRO
by Tiziano Lattisi
mercoledì 13 febbraio 13

2. WHAT IS JPA2
Java Persistence API
JPA2 in Java EE 6 (JPA1 in Java EE 5)
It’s a O/RM (Object Relational Mapping)
Framework to provide persistence
An object is a row in a master table (...)
mercoledì 13 febbraio 13

3. AND...
annotation || XML descriptor (configuration by exception)
POJO (Plain Old Java Object) based
Outside container (no server required)
No Bean interface required (no implements Serializable)
Different persistence providers (Hibernate, EclipseLink, ...)
mercoledì 13 febbraio 13

4. CASE STUDY: LIBRARY
The library contains several books
The library can loan one or more books to a person
Actors: Library, Book, Person, Loan
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5. O/RM
public class Person {
private Long id; PERSON
private String name;
PK ID
private String surname;
private Date birthday;
? NAME
private Collection<Loan> loanCollection;
SURNAME
public Person() {} GENRE
/* accessor methods */
} LOAN
public class Loan { PK ID
private Long id; FROMDATE
private Date fromdate;
private Date todate; TODATE
private Person person; FK PERSON
private Book book;
FK BOOK
public Loan(){ }
}
BOOK
public class Book { PK ID
private Long id;
private String title; TITLE
private String description; DESCRIPTION
public Book(){ } GENRE
}
mercoledì 13 febbraio 13

6. O/RM
to map variables to database columns
to handle data types between database and Java
to map tables references in relationship between objects
to manage the cycle of life of the object
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7. PERSISTENCE.XML
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0" xmlns:xsi="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_2_0.xsd">
<persistence-unit name="DemoPU" transaction-type="RESOURCE_LOCAL">
<provider>org.eclipse.persistence.jpa.PersistenceProvider</provider>
<properties>
<property name="javax.persistence.jdbc.url" value="jdbc:h2:mem:demo"/>
<property name="javax.persistence.jdbc.driver" value="org.h2.Driver"/>
<property name="javax.persistence.jdbc.user" value=""/>
<property name="javax.persistence.jdbc.password" value=""/>
<property name="eclipselink.ddl-generation" value="create-tables"/>
</properties>
<class>com.axiastudio.pypapi.demo.entities.Book</class>
<class>com.axiastudio.pypapi.demo.entities.Loan</class>
<class>com.axiastudio.pypapi.demo.entities.Person</class>
</persistence-unit>
</persistence>
mercoledì 13 febbraio 13

8. IDE HELPS US
example:
PU setup in
Netbeans 7.2 IDE
mercoledì 13 febbraio 13

9. BY ANNOTATION
@Entity
@Table(name = "person")
public class Person implements Serializable {
@Id
@GeneratedValue(strategy=GenerationType.AUTO)
@Column(name = "id")
private Long id;
@Column(name = "name")
private String name;
@Column(name = "surname")
private String surname;
@Column(name = "birthday")
@Temporal(TemporalType.DATE)
private Date birthday;
@OneToMany(mappedBy = "person", orphanRemoval = true, cascade=CascadeType.ALL)
private Collection<Loan> loanCollection;
public Person() { }
/* accessor methods */
}
mercoledì 13 febbraio 13

10. BY XML DESCRIPTOR
<entity-mappings>
...
<entity class="com.axiastudio.pypapi.demo.entities.Person"
metadata-complete="true">
<table-name="PERSON"/>
<attributes>
<id name="id"/>
<id name="name"/>
<id name="surname"/>
<id name="birthday"/>
<id name="id"/>
</attributes>
</entity>
</entity-mappings>
mercoledì 13 febbraio 13

11. SEQUENCE
by annotation
@SequenceGenerator(name="genBook", sequenceName="book.book_id_seq",
initialValue=1, allocationSize=1)
@Id
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator="genBook")
private Long id;
by descriptor
<id name="id">
<generated-value strategy="SEQUENCE" generator="genBook"/>
<sequence-generator name="genBook" sequence-name="book.book_id_seq"/>
</id>
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12. INSERT
import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;
import com.axiastudio.pypapi.demo.entities.Book;
import com.axiastudio.pypapi.demo.entities.Genre;
EntityManagerFactory emf = Persistence.createEntityManagerFactory("DemoPU");
em = emf.createEntityManager();
Book book = new Book();
book.setTitle("Dubliners");
book.setDescription("a collection of 15 short stories");
book.setGenre(Genre.ROMANCE);
em.getTransaction().begin();
em.persist(book);
em.getTransaction().commit();
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13. SELECT
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Book> cq = cb.createQuery(Book.class);
TypedQuery<Book> tq = em.createQuery(cq);
List<Book> books = tq.getResultList();
for( Book book: books ){
switch (book.getDescription()) {
case "Anna Karenina":
assert "ROMANCE".equals(book.getGenre().toString());
break;
case "Pro JPA":
assert "REFERENCE".equals(book.getGenre().toString());
break;
}
}
}
mercoledì 13 febbraio 13

14. SELECT (CRITERIA)
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Book> cq = cb.createQuery(Book.class);
Root from = cq.from(Book.class);
// from.get("description")
Predicate predicate = cb.like(from.get(Book_.description), "%very%");
cq = cq.where(predicate);
TypedQuery<Book> tq = em.createQuery(cq);
List<Book> books = tq.getResultList();
assert books.size() == 1;
assert "Anna Karenina".equals(books.get(0).getTitle());
Book book = tq.getSingleResult();
assert "Anna Karenina".equals(book.getTitle());
mercoledì 13 febbraio 13

15. UPDATE
CriteriaBuilder cb = em.getCriteriaBuilder();
CriteriaQuery<Person> cq = cb.createQuery(Person.class);
Root from = cq.from(Person.class);
cq = cq.where(cb.and(cb.equal(from.get(Person_.name), "Tiziano"),
cb.equal(from.get(Person_.surname), "Lattisi")));
TypedQuery<Person> tq = em.createQuery(cq);
Person person = tq.getSingleResult();
assert "Tiziano".equals(person.getName()); assert person.getEmail() == null;
Long key = person.getId();
person.setEmail("tiziano.lattisi@gmail.com");
Person personByKey = em.find(Person.class, key);
assert "tiziano.lattisi@gmail.com".equals(personByKey.getEmail());
em.detach(person);
person = em.find(Person.class, key);
assert ! "tiziano.lattisi@gmail.com".equals(person.getEmail());
person.setEmail("tiziano.lattisi@gmail.com");
em.getTransaction().begin(); em.merge(person); em.getTransaction().commit();
Person personByKey2 = em.find(Person.class, key);
assert "tiziano.lattisi@gmail.com".equals(personByKey2.getEmail());
mercoledì 13 febbraio 13

16. DELETE
Person person = new Person();
person("Tiziano");
person("Lattisi");
em.getTransaction().begin();
em.persist(person);
em.getTransaction().commit();
Long aPrimaryKey = person.getId();
[...]
Person person = em.find(Person.class, aPrimaryKey);
em.getTransaction().begin();
em.remove(person);
em.getTransaction().commit();
person = em.find(Person.class, aPrimaryKey);
assert person == null;
mercoledì 13 febbraio 13

17. AND NOW...
Thank you.
Tiziano Lattisi
Me: http://www.linkedin.com/in/tizianolattisi/
Slides: http://www.slideshare.net/lattisi/
Examples: http://tinyurl.com/crn3wwq
mercoledì 13 febbraio 13