JPA2 BRIEF INTROby Tiziano Lattisi

mercoledì 13 febbraio 13

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 (...)

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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, ...)

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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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O/RM

PERSONPERSONPK ID

NAMESURNAMEGENRE

public class Person { private String name; private String surname; private Date birthday;

public Person() {} /* accessor methods */}

public class Loan { private Date fromdate; private Date todate;

public Loan(){ }}

public class Book { private String title; private String description;

public Book(){ }}

LOANLOANPK ID

FROMDATETODATE

BOOKBOOKPK ID

TITLEDESCRIPTIONGENRE

?private Long id;

private Long id;

private Long id;

private Collection<Loan> loanCollection;

private Person person;private Book book;

FK PERSONFK BOOK

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O/RM

to manage the cycle of life of the object

to map variables to database columns

to map tables references in relationship between objects

to handle data types between database and Java

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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>

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IDE HELPS US

example:

PU setup in Netbeans 7.2 IDE

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BY ANNOTATION

public class Person {

private Long id;

private String name;

private String surname;

private Date birthday;

private Collection<Loan> loanCollection;

public Person() { } /* accessor methods */}

@Table(name = "person") implements Serializable

@GeneratedValue(strategy=GenerationType.AUTO) @Column(name = "id")

@Column(name = "name")

@Column(name = "surname")

@Column(name = "birthday")

@Entity

@Id

@Temporal(TemporalType.DATE)

@OneToMany(mappedBy = "person", orphanRemoval = true, cascade=CascadeType.ALL)

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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>

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SEQUENCE

@SequenceGenerator(name="genBook", sequenceName="book.book_id_seq", initialValue=1, allocationSize=1)

@Id@GeneratedValue(strategy = GenerationType.SEQUENCE, generator="genBook")private Long id;

<id name="id"> <generated-value strategy="SEQUENCE" generator="genBook"/> <sequence-generator name="genBook" sequence-name="book.book_id_seq"/></id>

by annotation

by descriptor

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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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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;

} }}

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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());

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UPDATECriteriaBuilder 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());

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DELETEPerson 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;

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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