Java e i database: da JDBC a JPALucio Benfante

lucio benfante.com@

verona.javaday.it www.jugpadova.it

database...chi era costui?

Application 1

The database and the applications

database

Application 2

Application 3

anotherdb

Atomicity

Consistency

Isolation

Durability

personid first_name last_name father born_in

1 Lucio Benfante 101

2 Giacomo Puccini 3 102

3 Michele Puccini 102

4 Antonio Puccini 2 103

city

id name

101 Venezia

102 Lucca

103 Milano

Relational databases

father

0

n

born_in_city

n 1

The term relational database was originally defined and coined by Edgar Codd at IBM Almaden Research Center in 1970.

SQL: Structured Query Language

SELECT first_name, last_name FROM person WHERE last_name = 'Puccini' ORDER BY first_name;

INSERT INTO person VALUES (5, 'Mario', 'Rossi', NULL, NULL);

DELETE FROM person WHERE id = ;1

UPDATE person SET first_name = 'Carlo' WHERE id = ;1

...and much more, included Data Definition Language (DDL).

RelationalDatabase Management Systems (DBMS)

DB2

InformixDynamic Server

DBMSApplication

specificDBMS

protocol

(just a small selection)

Java DataBase Connectivity(JDBC)

OracleDBMS

protocol

Application

OracleDBMS

OracleJDBC Driver

PostgreSQLJDBC Driver

PostgreSQLDBMS

PostgreSQLDBMS

protocol

JDBC API

JDBC Getting a connection

Class.forName("org.postgresql.Driver" );

Connection con = DriverManager.getConnection ( “jdbc:postgresql://localhost/javaday”, “username”, “password”);

JDBCExecuting an SQL statement

PreparedStatement ps = con.prepareStatement( "SELECT FROM Person WHERE last_name=* ?”);

ps.setString( , 1 "Puccini");

ResultSet rs = ps.executeQuery();

JDBCRetrieving your data

while ( rs.next() ) {

String firstName = rs.getString(“first_name”);

String lastName = rs.getString(“last_name”);

long fatherId = rs.getLong(“father”);

...etc.etc....}

JDBCAll together

Connection con=null;try { Class.forName( "com.mioDbms.mioDriver" ); con = DriverManager.getConnection ( “jdbc:...”, “user”, “pass”); PreparedStatement ps = con.prepareStatement( "SELECT FROM Person WHERE name=?”);* ps.setString( , "Lucio Benfante");1 ResultSet rs = ps.executeQuery(); while ( rs.next() ) rs.getString...ecc..ecc.... { } rs.close(); ps.close(); stmt.close(); catch(Exception e) ...} { finally } {

try { If (con != null) { con.close(); } catch( Exception ignoreMe ) } {}}

Object Relational Mapping (ORM)

ORM

HibernateMapping with XML

class name="Person" table="PERSON"< > id name="id" column="ID"< > generator class="native"/< > /id< > property name="firstName" column=”FIRST_NAME”/< > property name="lastName" column=”LAST_NAME”/< > many-to-one name=”father”< column=”FATHER”/> many-to-one name=”bornIn”< column=”BORN_IN” class=”City”/>/class< >

HibernateGetting your objects

SessionFactory sf = new Configuration().configure().buildSessionFactory();

Session session = sf.openSession();Transaction tx = session.beginTransaction();Query q = session.createQuery( “from Person p where p.lastName = :lastName”);q.setString(“lastName”, “Puccini”);List people = q.list();// here you'll have a list of persistent Person objects

Person person = ((Person)people.get( ))0City city = person.getBornIn();person.setFirstName(“Pippo”);

tx.commit();session.close();

sf.close();

HibernateCreating new records

Session session = sf.openSession();Transaction tx = session.beginTransaction();

Person person = new Person(“Lucio”, “Benfante”);session.save(person);

tx.commit();session.close();

HibernateConfiguration

!DOCTYPE hibernate-configuration PUBLIC<"-//Hibernate/Hibernate Configuration DTD 3. //EN"0"http://hibernate.sourceforge.net/hibernate-configuration-3. .dtd"0 >hibernate-configuration < >

session-factory< > !-- Database connection settings --< > property name=< "connection.driver_class">org.postgresql.Driver /property< > property name=< "connection.url">jdbc:postgresql://localhost/javaday /property< > property name=< "connection.username">username /property< > property name=< "connection.password">password /property< > !-- SQL dialect --< > property name=< "dialect">org.hibernate.dialect.PostgreSQLDialect /property< > !-- Echo all executed SQL to stdout --< > property name="show_sql" true /property< > < > !-- Create/Update the database schema on startup --< > property name=< "hbm2ddl.auto">update /property< > mapping resource=< "com/myproject/Person.hbm.xml"/> mapping resource=< "com/myproject/City.hbm.xml"/> /session-factory< >/hibernate-configuration< >

Look at our layers now

OracleDBMS

protocol

Application

OracleDBMS

OracleJDBC Driver

PostgreSQLJDBC Driver

PostgreSQLDBMS

PostgreSQLDBMS

protocol

JDBC API

ORM

●Hibernate●iBatis●JPA

− Hibernate− Toplink Essentials− EclipseLink− OpenJPA

●...

Java Persistence API (JPA)

A standard ORM in Java Enterprise Edition (JEE5)

JPAMapping with annotations

Entity@public class Person implements Serializable { Id@ GeneratedValue(strategy = GenerationType.AUTO)@ Basic(optional = false)@ private Integer id;

Column(name = "first_name")@ private String firstName;

Column(name = "last_name")@ private String lastName;

JoinColumn(name = "born_in", referencedColumnName = "id")@ ManyToOne@ private City bornIn;

OneToMany(mappedBy = "father")@ private Collection Person children;< >

JoinColumn(name = "father", referencedColumnName = "id")@ ManyToOne@ private Person father;

// ... normal getters and setters

// equals and hashCode implementation}

Hibernateor

JPA?

References

● www.hibernate.org

● http://java.sun.com/docs/books/tutorial/jdbc/index.html

● http://java.sun.com/javaee/5/docs/tutorial/doc/

● “Java Persistence with Hibernate”, Christian Bauer and Gavin King, Manning, 2007

● www.parancoe.org